hmi - b 584

BENSCEXPERIMENTAL REPORTS

2001

edited byY. Kirschbaum, M. Tovar, D. Bischoff and R. Michaelsen

Berlin Neutron Scattering CenterHahn-Meitner-Institut Berlin

May 2002

Berichte des Hahn-Meitner-Instituts Berlin

HMI - B 584

ISSN 0936 - 0891

Cover picture:

Diffuse scattering from a [Co/CoO/Au]20 multilayer measured via polarized neutron reflectometry(PNR)

Experiments were performed at the V6 reflectometer at the HMI using a position sensitive detector (PSD).The image shows a perspective view of an ainitial (incoming angle) - afinal (scattering angle) scan. Thediagonal “mountain range” corresponds to the specular reflected intensity as a function of the incomingangle (Q-2Q scan). For further details see p. 95.

The cover was designed by screenworks, www.screenworks.de

Editorial:

The Berlin Neutron Scattering Center(BENSC) is a department of theHahn-Meitner-Institut Berlin GmbH.BENSC develops and runs theNeutron Scattering Instruments at theBerlin Research Reactor BER II and isresponsible for the service to externalusers.The Hahn-Meitner-Institute (HMI) is anational research institution financedby the Federal Republic of Germanyand the City State of Berlin.

Address:

Berlin Neutron Scattering CenterBENSCThe Scientific SecretaryDr. Rainer MichaelsenHahn-Meitner-InstitutGlienicker Strasse 100D – 14109 Berlin (Wannsee)

Phone:

Fax:

Email:

Net:

+49 - 30 - 8062 3043, -2304

+49 - 30 - 8062 2523

[email protected]

http://www.hmi.de/bensc

II

CONTENTS

Introduction IV

List of BENSC Instruments VI

How to apply for BENSC beam time VIII

Acknowledgement for Support by the European Commission IX

List of Contributed Reports X

Part I: EXPERIMENTAL REPORTS 2001

Experimental Reports

Magnetism 1

Magnetic Structure and Magnetic Phase Transitions 1

Magnetic Excitations 72

Magnetic Thin Films 87

Structure 96

Chemical Structure 96

Structural Excitations 106

Soft Matter 120

Biology 152

Material Science and Industrial Applications 175

Instrument Development 213

Part II: LIST OF BENSC PUBLICATIONS

Papers 2000 (supplement), 2001, 2002 (preview) 236

Conference Contributions & Seminar Talks, Posters 2001 253

Theses 2001 278

AUTHOR INDEX 280

III

Introduction

The present volume contains 229 BENSCExperimental Reports and gives anoverview on the experimental work carriedout on BENSC during the year 2001.

BENSC User Service

BENSC is open to both, the national and theinternational user community, wherebyabout 70 percent of the beam time isavailable to external users; 20% for longterm collaborating groups from Germanuniversities and other research institutionsand 50 % for peer reviewed short termprojects.Detailed descriptions of all essential BENSCneutron scattering instruments are available- permanently updated - on the BENSCWebpage.

h t t p: / / ww w. hm i . de / b en s c / i ns t r um en t a t i on

The recently updated four colour printedversion (brochure HMI-B 577) is on themarket since March 2001 and available onrequest..

BENSC puts special emphasis on sampleenvironment under extreme conditions: highfields, high pressure, high, low and ultra lowtemperatures. The sample environmentgroup has published a detailed technicalhandbook on BENSC sample environment.The handbook is updated continuously andavailable in the INTERNET under

http://www.hmi.de/bensc/sample-env/home.html

Scientific Selection Panel

The short term project beam timeallocations for the scheduled instrumentsare established on a semi-annual basis incollaboration with a scientific selectionpanel, the 'user committee'. The 2001 beamtime quota for the short term projects of theexternal user groups were allocated at twouser committee sessions in November 2000and May 2001. Eleven external and two in-house committee members have beeninvolved:

External members:

Prof. Dr. P. Baglioni,Univ. Firenze, Italy

Prof. Dr. G. Decher, (May. 2001)Univ. Strasbourg, France

Prof. Dr. P. Fratzl,Univ. Leoben, Austria

Prof. Dr. Gottstein (Nov. 2000)RWTH Aachen, Germany

Prof. Dr. M. Jansen,Max-Planck-Institut für Festkörperforschung,Stuttgart, Germany

Prof. Dr. D. Kaczorowski,Polish Acad. of Sciences, Wroclaw, Poland

Prof. Dr. W. PrandlUniv. Tübingen, Germany

Dr. H. Riegler (Nov 2000)Max-Planck-Institut für Kolloid- undGrenzflächenforschung, Golm, Germany

Dr U. SteigenbergerCCLRC, ISIS, Rutherford Appleton Lab., U.K.

Prof. Dr. B. Stühn (Nov 2000)Techn. Univ. Ilmenau, Germany

Prof. Dr. B. Toudic,Univ. Rennes I, France

Internal members:

Prof. Dr. F. Mezei,HMI-Berlin

Dr. H.A. GrafHMI-Berlin

Support for European Access to BENSCfrom the European Commission

The access of European research groups toBENSC is generously supported by theEuropean Community. under the Access toResearch Infrastructures action of theHuman Potential Programme (IHP). UnderIHP the EU support is no longer restrictedon groups from (West-) European MemberStates, but also groups from the 10 Centraland Eastern European Associated States(Bulgaria, Czech Republic, Estonia,Hungary, Latvia, Lithuania, Poland,Romania, Slovenia, Slovakia) are eligible.

The annual numbers for EU supportedaccess to BENSC are

90 user experiments/a with a total of620 instrument days/a, and200 visits/a of140 individual external users

As listed on page IX, an important proportionof the contributions in this volume report onEU supported experiments.

IV

V

We are happy to inform our European usersthat BENSC has been awarded acontinuation contract with the EU to provideaccess to the BENSC facilities. The newIHP-contract has increased value and iseffective until end of 2003.

ICNS '01 Munich

A prominent demonstration for theEuropean role of BENSC has occurred atthe International Conference on NeutronScattering (ICNS ‘01) in September 2001 atMunich, where external and internal BENSCusers handed in 140 contributions, morethan 16% of the total number of allconference contributions. More than 50% ofthese BENSC contributions are fromexternal users. The majority of these ICNScontributions will be published in 2002 in thepeer reviewed conference proceedings(Appl. Phys. A).

Rainer Michaelsen

List of BENSC Instruments

VI

Instruments in the Experiment Hall April 2002

No. Instrument ext. Tube Instrument Staff ext. Room

E 1 3-Axis Spectrometer with PolarizationAnalysis 3101

D 1N Hans A.GrafJens KlenkeSergej Danilkin

277831673167

LS 335LS 334LS 334

E 2 Flat-Cone- andPowder Diffractometer/ 3102(E2a: Neutron Photography)

R 1 Univ. Tübingen: Dietmar Hohlwein Jens-Uwe Hoffmann

27082185

A 241A 239

E 3 Residual Stress Analysis,Powder Diffractometer 3103

T 2 Rainer SchneiderTobias Poeste (co-op. TU Berlin)

30963069

A 132A 129

E 4 2-Axis Diffractometer 3104(/ E4a: Test Device)

R 2 Karel Prokes 2804 LR 138

E 5 4-Circle Diffractometer 3104 R 3 Anja Loose 2793 LR 129

E 6 Focusing Single CrystalDiffractometer 3105

T 4 Norbert StüßerJorge Hernandez-Velasco EU-IHP-ARI

31713016

LR 142LR 137

E 7 STRESS-SPEC (FRM II)(under construction)

D 1S Rainer Schneider 3096 A 132

E 8 Perfect Crystal Set-up 3109 NL 4 TFH Berlin: Wolfgang Treimer 2221 A 226

E 9 Fine Resolution Powder Diffractometer(FIREPOD)

T5 Daniel TöbbensMichael Tovar EU-IHP-ARI

27932768

LR 129LR 144

E 10 3He-Diffractometer (HELINE) D 1S Konrad SiemensmeyerSlavomir Mat'as EU-IHP-RTN

27573135

LS 132LS 133

Instruments in the Neutron Guide Hall

No. Instrument ext. Tube Instrument Staff ext. Room

V 1 Membrane Diffractometer3121

NL 1A Thomas Hauß co-op.Univ. DüsseldorfSilvia Dante TU Darmstadt

20712071

LS 333LS 333

V 2 3-Axis Spectrometer for Cold Neutrons(FLEX) 3122

NL 1B Peter VorderwischKlaus Habicht co-op. TU Darmstadt

21712807

A 334A 333

V 3 Time-of-Flight Spectrometer(NEAT) 3123

NL 2o Ruep LechnerJörg PieperArnaud Desmedt EU-IHP-ARI

278030733179

A 352A 348A 349

V 4 Small Angle Scattering Instrument(SANS)

3124

NL 3A Albrecht WiedenmannUwe Keiderling TU DarmstadtElvira Garcia-MatresArmin Hoell EU-IHP-ARI

2283233923393181

LR 211LR 209LR 209LR 245

V 5 Spin-Echo Spectrometer with Time ofFlight Option (SPAN) 3125

NL 4 Catherine Pappas 2046 A 346

V 6 Reflectometer2806

NL 4 Helmut FritzscheRoland Steitz co-op. MPI-KG GolmJens HauschildRumen Krustev co-op.TU Berlin

3141214929263077

LS 130A 221A 226A 223

B 7 Depth Profile Measurement Device3126

NL 1Bu Dietmar Fink 3029 K 134

B 8 n-Autoradiography 3121 NL 1A Birgit Schröder-Smeibidl 2337 GE 145

V 10 Ultra Low Temperature Diffractometer3126

NL 2u Konrad Siemensmeyer 2757 LS 132

V 12a Double-Crystal Diffractometer(bent crystal) 3131

NL 3B Wolfgang Treimer TFH BerlinMarkus Strobl TFH Berlin

22212490

A 319A 316

V12 b Double-Crystal Diffractometer(lamellar crystal) 3131

NL 3B TFH Berlin: Wolfgang Treimer 2221 A 319

V 13 Fundamental Physics NL 3B Robert Golub 2829 V 135

V 14 Mirror Test Device NL1Bo Thomas Krist 2045 A 233

Sample Environment Michael MeissnerPeter SmeibidlStefan Kausche EU-IHP-ARI

220430803133

LS 131LR 147LS 113

B 7

V 1

4

V 1

0

V 6

V 1

2b

V 1

2a

V 5

(S

PAN

)

V 1

3

V 2

(FLE

X)

V 3

(N

EAT

) V 4

(SA

NS

)

V 1

B 8

E 1

E 2

E 3

E 2

a

E 4

E 5

E 7

E 6

E 1

0(H

ELI

NE

)

E 8

E 9

(FIR

EP

OD

)

B 2

N0

1

2

3

4

5

m

Neutr

on G

uid

e H

all

Cold

Neutr

ons

Exp

erim

ent H

all

Therm

al N

eutr

ons

Hahn-M

eitn

er-

Inst

itut B

erlin

Berlin

Neutr

on S

cattering C

ente

r

VIII

How to Apply for BENSC Beam Time.

BENSC is open to both the national and the international user community with up to 70% of thebeam time available to external users. The main portion of this beam time is foreseen for shortterm research proposals. Applications for short term beam time will be examined by a scientificselection committee twice each year,

deadlines for submission of proposals are 15 March and 15 September.

Requests for urgent experiments (Directors's discretionary time) and for industrial use may besubmitted at any time.

Applications for BENSC beam time should be made electronically. The BENSC ONLINEPROPOSAL SUBMISSION (OPS) system is available in the internet via

h t t p : / / w w w . h m i . d e / b e n s c / u s e r - i n f o / u s e r - i n f o _ e n . h t m l

Further information on BENSC instrumentation can be obtained from the internet via

h t t p : / / w w w . h m i . d e / b e n s c / i n s t r u m e n t a t i o n / i n s t r u m e n t a t i o n _ e n . h t m l

The latest four-colour printed version of the instrumentation brochure (HMI-B 577) is on the

market since March 2001 and available on request:

BENSC-HMIOffice of the Scientific SecretaryGlienicker Str. 100D - 14109 Berlin (Wannsee)Germany

Phone +49 - 30 - 8062 2304

Fax: +49 - 30 - 8062 2523

Email: [email protected]

The BENSC Experimental Reports are intended as interim summaries. In view of the short time availablebetween the termination of certain experiments and the deadline for this report, the results presentedhere have to be considered as very preliminary. The inclusion of reports in this volume does notconstitute a publication in the usual sense. Final results will be submitted for publication in regular

scientific journals.

Acknowledgement for Support by the European Commission

I

FP5, IHP, Access to Research Infrastructures

For most of the groups from European Community Member States and Associated States, the access to BENSC has beensupported by the European Community under the

Access to Research Infrastructure Action of the Improving Human Potential Programme (IHP),contract number HPRI-CT-1999-00020, period 2/00 - 1/03

Results of IHP supported groups are contained in almost 90 reports of this volume.

IHP-no

p. authors affiliation

046 84 Gratz et al. TU Wien, A050 76 Roennow et al. CEA-Grenoble, F058 133 Guenet et al. ICNRS Strabourg, F062 78 Bourdarot et al. CEA Grenoble, F065 2 Petrenko et al. Univ. Warwick, UK070 112 Powell et al. Univ. Durham, UK071 177 Girardin et al. Univ. Ancona, IT073 132 Triolo et al. Univ. Palermo, IT075 139 Faraone et al. Univ. Messina, IT118 107 Gratz et al. TU Wien, A119 42 Gratz et al. TU Wien, A120 106 Kaisermayr et al. Univ. Wien, A121 88 Temst et al. KU Leuven, B122 89 Temst et al. KU Leuven, B123 11 Svoboda et al. CU., Prague, CZ124 5 Nørgaard-Toft et al. Risø, DK125 26 Nørgaard-Toft et al. Risø, DK126 70 McMorrow et al. Risø, DK129 12 Lappas et al. FORTH, Heraklion, EL130 103 Moukarika et al. Univ. Ioannina, EL131 27 Roennow et al. CEA-Grenoble, F132 69 Roennow et al. CEA-Grenoble, F136 91 Mangin et al. LPM Nancy, F137 150 Torok et al. RSSO Bucharest, RO138 179 Girardin et al. Univ. Ancona, IT139029

152 Baglioni et al. Univ. Florence, IT

140 121 Triolo et al. Univ. Palermo, IT141 127 Calandrini et al. INFM Parma, IT142 123 Triolo et al. Univ. Palermo, IT143 164 Magazù et al. Univ. Messina, IT144 165 Baglioni et al. Univ. Florence, IT146 1 Jansen et al. Univ. Amsterdam, NL147 43 Janssen et al. Univ. Amsterdam, NL148 44 Gubbens et al. TU Delft, NL149 61 Tomuta et al. Leiden Univ., NL150 166 Bouwman et al. IRI Delft Univ., NL151 149 Raposo et al. FCT/UN Lisbon, P152 13 Przenioslo et al. Warsaw Univ., PL153 45 Szytula et al. JU Krakow, PL154 46 Szytula et al. JU Krakow, PL155 3 Cowley et al. Univ. Oxford, UK156 87 Lohstroh Univ. Oxford, UK157 4 Goff et al. Univ. Liverpool, UK158 155 Bradshaw et al. Univ. Edinburgh, UK

IHP-no

p. authors affiliation

161 109 McEwen et al. Univ. Coll. London, UK162 124 Arrighi et al. HW-U. Edinb., UK163 140 Martin et al. RAL, ISIS, UK164 151 Zabakhsh et al. Univ. London, UK183 108 Gratz et al. TU Wien, A184 50 Gratz et al. TU Wien, A185 90 Temst et al. KU Leuven, B186 191 Sittner et al. CAS IP, CZ187 206 Saroun CAS NPI, CZ188 18 Svoboda et al. CU, Prague,CZ189 51 Kolomiyets et al. Charles U., Prague,CZ190 171 Steriotis et al. NCRS Demokritos, EL191 32 Moshopoulou et al. NCSR Demokritos, EL192 48 Moshopoulou et al. NCSR Demokritos, EL193194

74 Lappas et al. FORTH, Heraklion, EL

195 115 Guillaume et al. Univ. Bordeaux, F196 117 Lassegues et al. Univ Bordeaux, F200 92 Mangin et al. LPM Nancy, F202 118 Padureanu et al. NIPNE-HH Bucharest, RO

204 178 Girardin et al. Univ. Ancona, IT207 122 Triolo et al. Univ. Palermo, IT208 120 Aliotta et al. CNR ITS Messina, IT209 128 Calandrini et al. INFM Parma, IT210 194 Moze et al. Univ. Modena, IT211 195 van Dijk et al. TU Delft, NL212 63 Nieuwenhuys et al. Leiden Univ., NL213 62 Tomuta et al. Leiden Univ., NL214 196 Pham et al. Univ. Amsterdam, NL215 52 Baran et al. JU Krakow, PL216 53 Szytula et al. JU Krakow, PL217 54 Szytula et al. JU Krakow, PL218 55 Szytula et al. JU Krakow, PL219 65 Szymczak et al. PAS IP Wasaw, PL221 192 Zrník et al. TU Kosice, SK222 56 Flachbart IEP Kosice, SK223 156 Davies et al. Univ. Edinburgh, UK224 125 Arrighi et al. HW-U. Edinb., UK225 126 Arrighi et al. HW-U. Edinb., UK226 137 Cosgrove et al. Univ. Bristol, UK227 33 Boothroyd et al. Oxford Univ., GB228 57 Hofmann et al. ISIS, UK230 81 Coldea et al. Univ. Oxford, UK231 82 Tennant et al. Univ. Oxford, UK233 71 Lake et al. Univ. Oxford, UK

IX

List of Contributed Experimental Reports

PAGE TITLE TEAM PROPOSAL

MagnetismMagnetic Structure and Magnetic Phase Transitions

1 Magnetic Structure of DyCo10V2 Y. Janssen1

J. Klenke2

S. Danilkin2

1Univ. Amsterdam, NL2HMI Berlin

E1 PHY- 01-0962

2 Magnetic Field Induced Ordering inthe Frustrated Antiferromagnet:Gadolinium Gallium Garnet

O. Petrenko1

J. Klenke2

P. Smeibidl2

1Univ. Warwick, UK2HMI Berlin

E1 PHY- 02-0273

3 Magnetic Structure of Laves Phase:Superlattices in a Magnetic Field

R. CowleyM. BentallW. Lohstroh

Oxford Physics, UK E1 PHY- 02-0285

4 Long Range Magnetic Order inIntermediate Valence CeLu Alloys

J. GoffP. DeenA. Toader

Univ. of Liverpool, UK E1 PHY- 02-0286

5 ErNi2B2C Interaction betweenSuperconductivity and Magnetism

K. Norgaard Toft1

A.B. Abrahamsen1

P. Smeibidl2

S. Kausche2

1Risoe Nat. Lab., DK2HMI Berlin

E1 PHY- 02-0289

6 Study of the Magnetic Phases ofCsCuCl3 for in-Plane Fields up to 17Tesla

N. StüßerA. HoserU. Schotte

HMI Berlin E1 EF

7 Rare Earth Induced Phase Transitionat HoMnO3

W. Prandl1

Th. Lonkai1

D. Hohlwein1,2

1Univ.Tübingen2HMI Berlin

E2 PHY- 01-0068

8 2D Ordering in YMnO3 W. Prandl1

Th. Lonkai1

D. Hohlwein1,2

1Univ. Tübingen2HMI Berlin

E2 PHY- 01-0068

9 Single Crystal Studies on HoMnO3 W. Prandl1

Th. Lonkai1

D. Hohlwein1,2


E2 PHY- 01-0068

10 Detailed Investigation of theCrystalline and Magnetic Structure ofDy0.5Tb0.5Cu2

A. SchneidewindR. SchedlerU. Witte

TU Dresden E2 PHY- 01-0945

11 Details of Magnetic Phase Diagram ofTmCu2 Single Crystal

P. SvobodaJ. Vejpravova

Charles Univ. Prague, CZ E2 PHY- 01-0947

12 A Neutron Diffraction Study of theTransition from the Spin-Gap toMagnetic Long Range Order in thePbNi2-xAxV2O8 (A=Mg, Co) Materials

A. Lappas1

I. Mastoraki1

J. Giapintzakis1

D. Többens2

R. Schneider2,3

J.-U. Hoffmann2,3

1FORTH, Heraklion, EL2HMI Berlin3Univ. Tübingen

E2E9

PHY- 01-0948

13 Modulated Magnetic Structure inCaCuxMn7-xO12 with Magnetic Fields

R. Przenioslo1

I. Sosnowska1

M. Regulski1

R. Schneider2,3

1Warsaw Univ., PL2HMI Berlin3Univ. Tübingen

E2 PHY- 01-0949

14 Magnetic Structure of the 1-D MagnetNa2MnF5

J. Pebler1

A. Krimmel21PU Marburg2Univ. Augsburg

E2 PHY- 01-1011

15 B-T Phase Diagram of the 1-DMagnet Na2MnF5

J. Pebler1

A. Krimmel21PU Marburg2Univ. Augsburg

E2 PHY- 01-1012

16 Magnetic Order in CeCu2(Si1-xGex)2 O. Stockert1

M. Deppe1

D. Hohlwein2

R. Schneider2,3

P. Smeibidl2

1MPI CPfS Dresden2HMI Berlin3Univ. Tübingen

E2 PHY- 01-1014

17 Magnetic Structure of CePt5Ge3 andCePd5Ge3

O. Stockert1

Z. Hossain1

M. Deppe1

D. Hohlwein2,3

P. Smeibidl2

1MPI CPfS Dresden2HMI Berlin3Univ. Tübingen

E2 PHY- 01-1015

X



18 Magnetic Phases of TmCu2 SingleCrystal in Horizontal Magnetic Field

P. Svoboda1

J. Vejpravová1

1CU Prague, CZ E2 PHY- 01-1016

19 Antiferromagnetic Order in UCu4Pd A. Krimmel Univ. Augsburg E2 PHY- 01-1046

20 Magnetic Correlations inLa0.9Sr0.1MnO3

J.-U. Hoffmann1,2

D. Hohlwein1,2

R. Schneider1,2

1HMI Berlin2Univ. Tübingen

E2 EF

21 Magnetic Diffuse Scattering inLa0.8Sr0.2MnO3

J.-U. Hoffmann1,2

D. Hohlwein1,2

R. Schneider1,2

1HMI Berlin2Univ. Tübingen

E2 EF

22 Magnetic Structures in Iron DopedY0,1Ca0.9MnO3

W. Prandl1

D. Hohlwein1,2


E2 EF

23 Spin Correlations and Interactions inthe Paramagnetic Phase of MnO

D. Hohlwein1,2 1HMI Berlin2Univ. Tübingen

E2 EF

24 Diffuse Magnetic Scattering above TC

in quasi-2D La1.2Sr1.8Mn2O7

T. Chatterji1

R. Schneider2,3

1ILL Grenoble, F2Univ. Tübingen3HMI Berlin

E2 EF

25 Paramagnetic Short-Range Order inTb

R. Schneider1,2

T. Chatterji31Univ. Tübingen2HMI Berlin3ILL Grenoble, F

E2 EF

26 A Structure Factor Study Looking fora Magnetic Moment on the NickelSite in TmNi2B2C

K. Norgaard Toft1

N.H. Andersen1

P. Smeibidl2

S. Kausche2

1Risoe, Roskilde, DK2HMI Berlin

E4 PHY- 01-0960

27 Single Crystal Study of theMagnetically Frustrated GadoliniumGallium Garnet

H.M. Roennow1

O.A. Petrenko2

1CEA-Grenoble, F2Univ. of Warwick, UK

E4 PHY- 01-0961

28 Magnetic Structure above theMetamagnetic Transition Field inHeavy Fermion SuperconductorUPd2Al3

N. Aso1

K. Prokes2

E. Garcia-Matres3

1NSL-ISSP Univ. Tokyo,JP2HMI Berlin3Univ. Augsburg

E4 MAT- 01-0963

29 Spin Structure Determination of theMetamagnet FeI2 in Applied MagneticField

K. Katsumata1

H. Aruga Katori1

K. Prokes2

1RIKEN, JP2HMI Berlin

E4 PHY- 01-0964

30 Disappearance of AntiferromagneticPhase due to Random Impurity Effectin CoNb2O6

S. Mitsuda1

H. Okano1

K. Prokes2

P. Smeibidl2

1Univ. Tokyo, JP2HMI Berlin

E4 PHY- 01-0965

31 Field-Induced Magnetic PhaseTransition in a Triangular LatticeAntiferromagnet CuFe0.98Al0.02O2 up to14.5T

S. Mitsuda1

N. Terada1

K. Prokes2

1Sience Univ., Tokyo, JP2HMI Berlin

E4 PHY- 01-1035

32 Neutron-Diffraction Study of Field-Induced Transitions in Ce2RhIn8

E. Moshopoulou1

J.L. Sarrao2

K. Prokes3

E. Garcia-Matres4

1NCSR Demokritos, EL2Los Alamos, CMTP, USA3HMI Berlin4Univ. Augsburg

E4 PHY- 01-1031

33 Investigation of the MagneticStructure of PrO2

A.T. BoothroydC.H. Gardiner

Oxford Univ., UK E4 PHY- 01-1034

34 Field-Induced Magnetic Structures inUNiGe

K. Prokes HMI Berlin E4 EF

35 Magnetic Structure in UCuGe SingleCrystal

K. Prokes1

A.V. Andreev2

1HMI Berlin2Charles Univ., Prague, CZ

E4 EF

36 Search for Field-Induced MagneticOrder in SuperconductingBi2Sr2CuO6+x

B. KeimerS. BayrakciC. UlrichB. Liang

MPI-FKF, Stuttgart E4 EF

XI



37 Structural and Magnetic Instabilitiesof La2-xSrxCaCu2O6

C. Ulrich1

B. Keimer1

M. Ohl2

M. Reehuis3

1MPI-FKF Stuttgart2ILL Grenoble, F3Univ. Augsburg

E5 PHY- 01-0973

38 Crystallographic and MagneticStructure of YVO3

C. Ulrich1

B. Keimer1

M. Reehuis2

1MPI-FKF Stuttgart2Univ. Augsburg

E5 PHY- 01-1040

39 Effects of Fe Additions on the HelixSpin-Structure of the MetamagneticCompound MnAu2

U.K. Rößler1

N. Stüßer2

A. Kreyßig3

1IFW Dresden2HMI Berlin3TU Dresden

E6 PHY- 01-0867

40 Neutron Diffraction Study of a Single-Crystalline UCu5Al Sample

V.H. Tran1

N. Stuesser2

M. Hofmann2

1ILTSR, PAS, Wroclaw, PL2HMI Berlin

E6 PHY- 01-0975

41 Magnetic and Crystallographic Orderin UPd1.85Sn

I. Maksimov1

S. Süllow1

R. Feyerherm2

1TU Braunschweig2HMI Berlin

E6 PHY- 01-0977

42 Magnetic Instability in RCo3

IntermetallicsE. Gratz1

A.S. Markosyan2

A. Hoser3

1Univ. Wien, A2Moscow State Univ., RU3RWTH Aachen

E6 PHY- 01-0978

43 Magnetic Structure of Ho2Co15Si2 J. Janssen1

N. Stüßer2

1Univ. Amsterdam, NL2HMI Berlin

E6 PHY- 01-0980

44 Magnetic Structure in TmCuAl P.C.M. Gubbens1

A. Mulders1

P. Javorsk_2

1TU Delft, NL2Univ. Prague, CZ

E6 PHY- 01-0981

45 Magnetic Structures ofNdMn2-xFexGe2 (x=0.3 and 0.4) as aFunction of Temperature andPressure

A. Szytula1

B. Penc1

N. Stüßer2

1Jagiellonian Univ.Krakov, PL2HMI Berlin

E6 PHY- 01-0982

46 Magnetic Structures and PhaseTransitions in RRhSi (R=Tb-Er)Compounds

A. Szytula1

L. Gondek1

B. Penc1

N. Stüßer2

1Jagiellonian Univ., Krakow,PL2HMI Berlin

E6 PHY- 01-0983

47 Onset of Ferromagnetic-like Behaviorin Nanostructured ZnFe2O4 - HighTemperature Magnetic Transitions

S.J. Campbell1

M. Hofmann2

1Univ. of NSW, Canberra,2ISIS, UK

E6 PHY- 01-0984

48 Search for Diffuse Intensity in theReciprocal Space of the Heavy-Fermion Compound Ce2RhIn8

E.G. Moshopoulou1

N. Stüßer2

J. Hernandez-Velasco2

E. Garcia-Matres3

1NCSR Demokritos, EL2HMI Berlin3Univ. Augsburg

E6 PHY- 01-1032

49 Temperature Dependence of theAntiferromagnetic Order Parameter ofFeWO4

U. Köbler1

A. Hoser2

1FZ Jülich2RWTH-Aachen

E6 PHY- 01-1045

50 Magnetic Instability in Er0.7Y0.3Co3 E. Gratz1

A. Hoser2

N. Stüßer3

1TU Wien, A2RWTH-Aachen3HMI Berlin

E6 PHY- 01-1048

51 Magnetic Structures and MagneticPhase Transitions in Tb6Co2Sn

O. KolomiyetsP. SvobodaP. Javorsk_V. Sechovsky

Charles Univ. Prague, CZ E6 PHY- 01-1049

52 Magnetic Structure and DomainFormation in ErAuGe

S. Baran1

N. Stüßer2


A. Szytula1

B. Penc1

J. Leciejewicz3

1Jagiellonian Univ.Krakow, PL2HMI Berlin3INCT, Warszawa, PL

E6 PHY- 01-1053

53 Neutron Diffraction Studies of RNiSn2

(R=Tb-Er) CompoundsA. Szytula1

B. Penc1

S. Baran1

J. Leciejewicz3

N. Stüßer2

1JU Krakow, PL2HMI Berlin3INCT, Warszawa, PL

E6 PHY-01-1055

XII



54 Neutron Diffraction Studies of RRhGa(R=Tb-Er) Compounds

A. Szytula1

B. Penc1


1JU Krakow, PL2HMI Berlin

E6 PHY- 01-1056

55 Neutron Diffraction StudyCe2Co1-xAuxSi3 (x=0.4, 0.6, 0.8, 1.0)

A. Szytula1

B. Penc1


1JU Krakow, PL2HMI Berlin

E6 PHY- 01-1057

56 Field Dependence of the MagneticStructure in Cubic Rare EarthDodecaborides

K. Flachbart1

K. Siemensmeyer2

S. Matas2

D. Günther2

M. Meissner2

1IEP Kosice, SK2HMI Berlin

V10E6

PHY- 01-1058

57 Valence and Magnetic Transitions inYbMn2Si2-xGex

M. Hofmann1

S.J. Campbell2

N. Stüßer3

1ISIS, UK1Univ. of NSW, Canberra3HMI Berlin

E6 PHY- 01-1059

58 Neutron Diffraction Study of MagneticPhase Transition in Mixed CrystalMn0.94Fe0.06WO4

D. Sangaa1

H. Ehrenberg3

H. Weitzel3

N. Stüßer2

1Nat. Univ. of Mongolia2HMI Berlin3TU Darmstadt

E6 PHY- 01-1060

59 Incommensurate Magnetic Order inErFe2Al10

M. Reehuis1

A. Krimmel1

A. Loidl1

M.W. Wolff2

W. Jeitschko2

1Univ. Augsburg2Univ. Münster

E6 EF

60 Influence of Alternating MagneticFields on the Bloch Walls in a NickelSingle Crystal

W. Treimer1

J. Peters1

A. Hilger2

1HMI Berlin2TFH Berlin

E8 EF

61 Crystalline- and Magnetic Structure ofFerroelectric Persovskites

D.G. Tomuta1

G.J. Nieuwenhuys1

R. Feyerherm2

1Leiden Univ., NL2HMI Berlin

E9 PHY- 01-0985

62 Crystalline- and Magnetic Structure ofFerroelectric Perovskites

D.G. Tomuta1

R. Hendrikx1

R. Feyerherm2

1KOL Leiden, NL2HMI Berlin

E9 PHY- 01-1064

63 Crystalline- and Magnetic Structure ofFerroelectromagnetic Perovskites

G.J. Nieuwenhuys1

D.G. Tomuta1

R. Feyerherm2

1KOL Leiden, NL2HMI Berlin

E6 PHY- 01-1052

64 Magnetic Phase Transitions in theAntiferromagnetic Oxides Embeddedin a Porous Glass

I. Golosovsky1

D. Többens2

M. Tovar2

1PNPI, Gatchina, RU2HMI Berlin

E9 PHY- 01-0995

65 Phase Transitions and PhaseSeparation in La(1-x)Ca(x)MnO(3-x/2)

(0<x<0.5)

H. Szymczak1

M. Tovar2

1PAS IP Warsaw, PL2HMI Berlin

E9 PHY-01-1072

66 Magnetic Structure ofMn(dca)2(pyz-d8) and other MolecularMagnets

R. Feyerherm1

A. Loose1

P. Smeibidl1

S. Raasch1

D. Többens1

J.L. Manson2

T. Ishida3

1HMI Berlin2ANL Argonne, USA3Univ. for E-C, Tokyo, JP

E6E9

EF

67 Magnetic Phase Diagram ofMn1-xFexWO4

E. Garcia-Matres1

N. Stüßer2

1Univ. Augsburg2HMI Berlin

E6E9

EF

68 Magnetic Structures in RETiGe(RE = Dy, Ho, Er) Compounds

K. Prokes1

K.H.J. Buschow2

1HMI Berlin2Univ. Amsterdam, NL

E9 EF

69 Search for Antiferromagnetic VortexCores in YBa2Cu3O6.54

H.M. Roennow1

B. Lake2

N.B. Christensen3

N.H. Andersen3

1CEA Grenoble, F2Oak Ridge Nat. Lab., USA3Risoe Lab. DK

V2 PHY- 02-0291

70 Vortex Core Signal in the SingleLayer High-TemperatureSuperconductorLa2-xSrxCuO4

D.F. McMorrow1

B. Lake2

N.B. Christensen1

K. Lefmann1

G. Aeppli3

1Risoe Nat. Lab., DK2Oak Ridge Lab., USA3NECR, Princeton, USA

V2 PHY- 02-0298

XIII


71 Vortex State in UnderdopedLa2-xSrxCuO4

B. Lake1,2

H.M. Roennow3

N.B. Christensen4

D.F. McMorrow4

G. Aeppli5

1ORNL, USA2Univ. Oxford, UK3ILL Grenoble, F4Risoe, DK5NECR, Princeton,USA

V2 PHY- 02-0322

Magnetic Excitations

72 Neutron Diffraction Study of the FieldInduced Order in Singlet-GroundState Magnet CsFeCl3

M. Toda1

Y. Fujii2

S. Kawano1

J. Klenke3

H.A. Graf3

M. Steiner3

1Kyoto Univ.,Osaka, JP2Univ. of Fukui, JP3HMI Berlin

E1 PHY- 02-0310

73 Supression of Quantum Fluctuationsby a Magnetic Field

M. Enderle1

K. Prokes2

1ILL Grenoble, F2HMI Berlin

E4 EF

74 The Interplay between CrystalStructure and the Spin-Gap in Low-Dimensional Oxides under High-Pressure

A. Lappas1

C.J. Nuttall1

D. Többens2


N. Stüßer2

1FORTH-IESL Heraklion, EL2HMI Berlin

E6E9

PHY- 01-1050/

01-1051

75 Quantum Critical Field Investigationsin the Unconventional S=1/2Antiferromagnet TlCuCl3

N. Cavadini1

Ch. Rüegg1

P. Vorderwisch2

P. Smeibidl2

1LNS ETHZ & PSI, CH2HMI Berlin

V2 PHY- 02-0280

76 Excitations in the High-Field Phase ofCuGeO3

H.M. Roennow1

M. Enderle2

K. Habicht3

P. Smeibidl3

1Risoe, DK2Univ. Saarbrücken3HMI Berlin

V2 PHY- 02-0281

78 Study of the Tiny Ordered MagneticMoment in URu2Si2 in High MagneticField

F. Bourdarot1

B. Fak1

G. Amoretti2

R. Caciuffo3

P. Santini4

1CEA Grenoble, F2Univ. Parma, IT3Univ. Ancona, IT4Oxford Physics, UK

V2 PHY- 02-0283

79 Unusual Low-Energy SpinFluctuations in an Underdoped HTC

Superconductor

B. Keimer1

C. Ulrich1

T. Keller1

K. Habicht2

1MPI Stuttgart2HMI Berlin

V2 PHY- 02-0288

80 Phase Diagram of a Novel Two-Dimensional Quantum HeisenbergAntiferromagnet

C. Broholm1

M.B. Stone1

P. Vorderwisch2

P. Smeibidl2

S. Kausche2

1John Hopkins Univ., USA2HMI Berlin

V2 PHY- 02-0296

81 High-Field Excitations in the XYQuantum Magnet Cs2CoCl4

R. Coldea1

C.J. Mukherji1

D.A. Tennant1,2

K. Habicht3

P. Smeibidl3

1Univ. Oxford, UK2ISIS, UK3HMI Berlin

V2 PHY- 02-0318

82 Stabilization of a 2D FractionalQuantum Spin Liquid State byMagnetic Field in Cs2CuCl4

D.A. Tennant1,2

R. Coldea1

K. Habicht3

P. Smeibidl3

1Univ. Oxford, UK2ISIS, UK3HMI Berlin

V2 PHY- 02-0319

83 Field-Driven Quantum Criticality in aS=1/2 Spin Liquid

N. Cavadini1

Ch. Rüegg1

K. Habicht2

M. Meissner2

S. Kausche2

1ETH & PSI, CH2HMI Berlin

V2 PHY- 02-0320

84 Wave Vector, Energy andTemperature Dependence of theSpin Fluctuation Dynamic in UAl2

E. Gratz1

B.D. Rainford2

N. Bernhoeft3

R.E. Lechner4

J. Ollivier4

1TU Wien, A2Univ.Southampton, UK3CEA, F4HMI Berlin

V3 PHY- 03-0140

XIV



85 Magnetic Excitations in a Mixed Mn(II, III) Tetrameric Cluster

H.-U. GüdelG. ChaboussantR. BaslerS. Ochsenbein

Univ. Bern, CH V3 CHE- 03-0164

86 Effects of Fe Addtions on the HelixSpin-Structure of the MetamagneticCompound MnAu2

U.K. Rößler1

A. Kreysig2

A. Hoell3

A. Heinemann3

1IFW Dresden2TU Dresden3HMI Berlin

V4 PHY- 04-0500

Magnetic Thin Films

87 Magnetic Ordering in YMn2 -SingleCrystalline Films

W. Lohstroh Oxford Univ. UK E1 PHY- 02-0294

88 Specular and Diffuse NeutronReflectivity of a Micropatterned CoAntidot Array

K. Temst1

J. Swerts1

H. Fritzsche2

1KU Leuven, B2HMI Berlin

V6 PHY- 04-0610

89 Neutron Reflectivity of a DiluteMagnetic Alloy Film

K. Temst1

C. van Hasendonck1

J. Swerts1

H. Frtizsche2


V6 PHY- 04-0611

90 Polarized Neutron ReflectivityAnalysis of Thin Films with ArtificiallyInduced Magnetic Roughness

K. Temst1

J. Swerts1

H. Fritzsche2


V6 PHY- 04-0664

91 Influcence of Magnetic Domain WallShape and Size on PolarisedNeutron Reflectometry in "ExchangeBias" like Sample

S. Mangin1

F. Montaigne1

H. Fritzsche2

1LPM Nancy, F2HMI Berlin

V6 PHY-04-0612

93 Determination of the MagneticReversal of (110)-oriented Fe-Layers

H. FritzscheJ. Hauschild

HMI Berlin V6 EF

94 Polarized Neutron Reflectometry ofa Pt/Co Bilayer

H. MalettaD. SchmitzJ. Hauschild

HMI Berlin V6 EF

95 Asymmetric Magnetization Reversalin a Co/CoO Exchange BiasMultilayer

M. Gierlings1

M. Gruyters1

D. Riegel1

H. Fritzsche1

M.J. Prandolini2

1HMI Berlin2FU-Berlin

V6 EF

StructureChemical Structure

96 Phase Transformations in Cu2-δSe S. Danilkin1

D. Hohlwein1,4

R. Schneider1,4

A. Skomorokhov2

N. Bickulova3

1HMI Berlin2IPPE, Obninsk, RU3SGPI, Sterlitamak, RU4Univ. Tübingen

E1E2

EF

97 Localization of Fluorine andHydrogen Atoms in the (NH4)2KGaF6

Elpasolite

A.D. Vasiliev1

D. Hohlwein2,3

M.L. Afanasiev1

M.V. Gorev1

I.N. Flerov1

1RAS Krasnoyarsk, RU2HMI Berlin3Univ. Tübingen

E2 PHY- 01-1017

98 The Determination of the Disorder ofthe Ammonium Ions in the Phase IIof Trirubidium Hydrogen Disulfate-Triammonium Hydrogen Disulfate

L. Smirnov1

V. Sarin2

K. Wozniak3

P. Dominiak3

1SUC SSC RF ITEP, RU2INR RAS, Moscow, RU3Univ. Warsaw, PL

E5 PHY- 01-0970/

01-0969

92 Magnetic Profile in Gd40Fe60 / TbxFe1-x

Exchange Coupled Bilayers Studiedby Polarised Neutron Reflectometry

S. Mangin1

F. Montaigne1

H. Fritzsche2

1LPM Nancy, F2HMI Berlin

V6 PHY- 04-0665

XV



100 Investigation of the PhaseTransition in a (NH4)[H5(PO4)2] SingleCrystal

S. Troyanov1

E. Kemnitz2

A. Loose4

M. Reehuis3

1Moscow State Univ., RU2HU Berlin3Univ. Augsburg4HMI Berlin

E5 CHE- 01-0971

101 High Temperature Structure ofMercallite

K. KnorrG. Lentz

CAU Kiel E5 GEO-01-1041

102 Metal Nitrides G. Auffermann1

R. Kniep1

Y. Prots1

R. Niewa1

M. Tovar2

1MPI CPFS, Dresden2HMI Berlin

E9 CHE- 01-0990

103 Cation Migration in Alkali-SaturatedMontmorillonites

A. Moukarika1

D. Gournis1

A. Lappas2

D. Többens3

1Univ. Ioannina, EL2FORTH, Heraklion, EL3HMI Berlin

E9 OTH- 01-0993

104 Study of the Metal Order in the SolidSolution Serie 2ZnS-CuInS2

S. Schorr1

M. Tovar2

1Univ. Leipzig2HMI Berlin

E9 PHY- 01-1067

105 Crystal Chemical Studies in theSpinel System CuCr2O4-NiCr2O4

M. Tovar1

C. Welker2

1HMI Berlin2Univ. Stuttgart

E9 EF

Structural Excitations

106 Ni-Diffusion in NiGa with NSE M. Kaisermayr1

C. Pappas2

G. Vogl2,1

A. Triolo2

1Univ. Wien, A2HMI Berlin

V5 PHY- 03-0169

107 Crystal Electric Field-LatticeInteraction

E. Gratz1

A. Hoser2

K. Hense1

C. Anzur1

1TU Wien, A2RWTH Aachen

E1 PHY- 02-0284

108 Crystal Electric Field-LatticeInteraction

E. Gratz1

A. Hoser2

K. Hense1

C. Anzur1

1TU Wien, A2RWTH Aachen

E1 PHY- 02-0306

109 CEF Excitations in Single CrystalPrNiSn

K.A. McEwen1

E. Beirne1

K. Habicht2

1Univ. College London, UK2HMI Berlin

V2 PHY- 02-0295

110 Search for quasielastic neutronscattering from NH3 rotors in theHofmann clathrate Ni-Ni-biphenyl

P. Vorderwisch HMI Berlin V2 EF

111 Q- and Temperature Dependence ofPhonon Linewidths in Single CrystalPb Measured with NeutronResonance Spin Echo (NRSE)

T. Keller1

B. Keimer1

K. Habicht2

R. Golub2

F. Mezei2

1MPI-FKF, Stuttgart2HMI Berlin

V2 EF

112 Proton Diffusion in Lanthanide(III)Doped Zeolite Y, a Contrast Agentfor Medical Imaging

D.H. Powell1

M. Gay-Duchosal2

J. Ollivier3

J. Pieper3

1Univ. of Durham, UK.2Univ. Lausanne, CH3HMI Berlin

V3 CHE- 03-0146

113 Anion Reorientation in SodiumPhosphate/Sodium Sulfate SolidSolutions

D. WilmerH. Feldmann

Univ. Münster V3 MAT- 03-0157

114 Quasielastic Scattering from anUnusual Methyl Group Linking AlAtoms in the Electron DeficiencyCompound [Al(CH3)3]2 ...

M. Prager1

A. Desmedt21FZ Jülich2HMI Berlin

V3 CHE- 03-0181

XVI



115 Molecular Dynamics in theIncommensurate 2-Decanone/UreaCrystal

F. Guillaume1

A. Desmedt21Univ. Bordeaux, F2HMI Berlin

V3 CHE- 03-0184

116 Dynamics of the ChlorocyclohexaneMolecules in their Thiourea InclusionCompound

A. Desmedt1

F. Guillaume2

J. C. Soetens2

R.E. Lechner1

1HMI Berlin2LPCM, Univ. Bordeaux, F

V3 EF

117 Protonic Conduction Mechanisms inPerchloric Acid Hydrate Clathrate

J.C. Lassegues1

A. Desmedt2

F. Guillaume1

D. Cavagnat1

R.E. Lechner2

1Univ. Bordeaux, F2HMI Berlin

V3 CHE- 03-0185

118 Neutron Scattering Investigation ofSuperconducting CeramicsBi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3Ox

I. Padureanu1

R. Lechner2

D. F. Aranghel1

A. Radulescu1

J. Pieper2

1NIPNE-HH Bucharest, RO2HMI Berlin

V3 MAT- 03-0189

119 The Investigation of MicroscopicDynamics of ZnCl2

M. Russina1

F. Mezei2

O. Russina2

R.E. Lechner2

J. Pieper2

A. Desmedt2

1LANSCE, USA2HMI Berlin

NEAT

EF

Soft Matter

120 Hydrogen-Bonded Structures inMethanol/CCl4 Mixtures

F. AliottaC. VasiF. SaijaR. Ponterio

CNR ITS Messina, IT E9 PHY- 01-1071

121 Segmental Dynamics in PolymerElectrolytes

R. Triolo1

A. Triolo2

F. Lo Celso1

1Univ. of Palermo, IT2HMI-BENSC

V3 MAT- 03-0159

122 QENS Study of the Dynamics ofConfined PEO-Salt Systems

R. Triolo1

A. Triolo2

V. Morreale1

V. Baiata1

J. Pieper2

1Univ. Palermo, IT2HMI-BENSC

V3 MAT-03-0188

123 Structural Microheterogeneities inPEO-Salt Mixtures

R. Triolo1

A. Triolo2

F. Lo Celso1

1Univ. Palermo, IT2HMI-BENSC

V4 MAT- 04-0590

124 Local Dynamics of Polyethylene V. Arrighi1

G. Arialdi2

F. Saggio1

1HW-Univ., Edinburgh, UK2ULB, Brussels, B

V3 CHE- 03-0160

125 Local Dynamics of SelectiveDeuterated Liquid CrystallinePolymers

V. Arrighi1

H. Qian1

A. Desmedt2

1HWU Edinburgh, UK2HMI Berlin

V3 CHE-03-0191

126 Collective Dynamics in AtacticPolypropylene

V. Arrighi1

F. Saggio1

P. Holmes1

A. Triolo2

C. Pappas2

1HWU Edinburgh, UK2HMI Berlin

V5 CHE-03-0197

127 Dynamic Features of HydrationWater Interacting with HydrophobicMolecules

V. Calandrini1

A. Deriu1

G. Onori2

R.E. Lechner3

J. Pieper3

1INFM Parma, IT2INFM Perugina, IT3HMI Berlin

V3 PHY- 03-0161

128 Dynamic Features of HydrationWater Interacting with HydrophobicMolecules

V. Calandrini1

A. Deriu1

G. Onori2

R.E. Lechner3

J. Pieper3

1Univ. Parma, IT2Univ. Perugia, IT3HMI Berlin

V3 PHY- 03-0186

XVII



129 Diffusion of Sheared Liquids M. Wolff1

A. Magerl1

B. Frick2

H. Zabel3

R.E. Lechner4

J. Pieper4

A. Desmedt4

1Univ. Erlangen2ILL Grenoble, F3RU Bochum4HMI Berlin

V3 PHY- 03-0182

130 Alignment of Lipid/Water SystemsUsing Magnetic Shear

J. Katsaras1

Th. Gutberlet2

Th. Hauss3

1NRC-CNRC, Chalk River2HMI Berlin3Univ. Düsseldorf

V1 PHY- 01-1004

131 Investigation of MixedLipid/Surfactant Aggregates inMagnetic Field

M. Kiselev1

Th. Gutberlet2

A. Hoell2

1FLNP JINR, RU2HMI Berlin

V4 BIO- 04-0656

132 PS-PEO Micelles as Reactors forMetal Nanoparticles Formation:A SANS Study

R. Triolo1

A. Triolo2

F. lo Celso1

1Univ. di Palermo, IT2HMI-BENSC

V4 CHE- 04-0551

133 Conformation in Solution of Side-Chain Liquid Crystal Polymers as aFunction of the Mesogen-graftAmount

J.-M. Guenet1

A. Brandt2

J.-D. Marty3

M. Mauzac3

D. Rousseau4

P. Martinoty4

1ICNRS Strasbourg, F2HMI Berlin3CNRS-UPS Toulouse, F 4CNRS-ULP Strasbourg, F

V4 PHY- 04-0545

134 SANS Study of the PolyelectrolyteLayers Structure for HollowCapsules

E. Donath1

I. Estrela-Lopis1

S. Leporatti1

P. Strunz2

A. Hoell2

1Univ. Leipzig2HMI Berlin

V4 BIO- 04-0631

135 New Organogels with Alkyl-Monogluco-Pyranosides

M. Gradzielski1

B. Hoffmann1

A. Zapf1

G. Platz1

U. Keiderling2

1 Univ. Bayreuth2 TU Darmstadt

V4 CHE- 04-0633

136 Formation of Silica Gels in thePresence of Cationic Additives andSurfactants

M. Meyer1

D. Gräbner2

U. Keiderling2

1Univ. Bayreuth2 TU Darmstadt

V4 CHE- 04-0636

04-0585

137 Adsorption of Non-Ionic Surfactantsonto Polystyrene Latex Particles

T. Cosgrove1

N. Nugent1

A. Nelson1

A. Hoell2

1 Univ. Bristol, UK2 HMI Berlin

V4 CHE- 04-0653

138 Aggregation of Cyclodextrins inAqueous Solution

B. Smarsly1

A. Hoell2

S. Polarz1

1MPI-KGF Golm/Potsdam2HMI Berlin

V4 PHY- 04-0734 LT

139 Characterization of TrehaloseAqueous Solutions by Neutron SpinEcho

C. Branca1

A. Faraone1

S. Mangione1

C. Pappas2

A. Triolo2

1 Univ.v. Messina, IT2 HMI-BENSC

V5 PHY-03-0152

140 Coherent Contribution in LiquidQuinoline as a Function ofTemperature

D. Martin1

C. Pappas2

1 RAL, ISIS, UK2 HMI Berlin

V5 PHY-03-0174

141 Studies on the SAM/WaterInterphase for Films with DifferentProtein Resistance

M. GrunzeD. SchwendelR. DahintT. Hayashi

Univ. Heidelberg V6 MAT-04-0609

142 Studies on the SAM/WaterInterphase for Monolayer Films ofDifferent Hydrophilicity

M. GrunzeD. SchwendelR. DahintT. Hayashi

Univ. Heidelberg V6 MAT- 04-0661

143 Critical Adsorption in Thin WettingFilms of a C6H14 /C6F14 Mixture

W. Press1

W. Prange1

R. Steitz2,3

1 CAU Kiel2 MPI-KGF Golm/Potsdam3 HMI Berlin

V6 PHY-04-0575

XVIII



144 Structure Characterization ofPolybutadiene-b-Poly(Ethyleneoxide) Micelles in thePresence of the AnionicCosurfactant SDS

A. Nordskog1

A. Brandt2

U. Keiderling3

1 TU Berlin2 HMI Berlin3 TU Darmstadt

V4 CHE- 04-0580

145 Structure of ThermosensitivePolymer Films at the Solid/LiquidInterface

R. von Klitzing1

R. Steitz2,3

1 TU Berlin2 MPI-KGF Golm/Potsdam3 HMI Berlin

V6 PHY-04-0607

146 Diblock Copolymers at the WaterSurface

C.A. HelmA. WesemannH. Ahrens

Univ. Greifswald V6 MAT- 04-0662

147 Adsorption of C8E4 to the Polymer-Solution Interface

R. Steitz2,3

G.H. Findenegg1

S. Schemmel1

1 TU Berlin2 MPI-KGF Golm/Potsdam3 HMI Berlin

V6 EF

148 Boundary Layer Structure of aniBA + D2O Mixture at theHydrophilic Silica Surface

R. Steitz2,3

G.H. Findenegg1

S. Schemmel1

1TU Berlin2 MPI-KGF Golm/Potsdam3HMI Berlin

V6 EF

149 Adsorption/Desorption ofPoly(o-methoxyaniline) Layer-by-Layer Films

M. RaposoP.A. Ribeiro

FCT/UN Lisbon, P V6 MAT- 04-0615

150 Fractal Structures in Poly(N-Vinylcaprolactam) AqueousSolutions Decomposed

G. Torok1

V.T. Lebedev2

A. Len1

1 RSSP, Budapest, HU2 PNPI Gatchina, RU

V12 CHE-

04-0601

151 Distribution of Glucose Oxidase inthe Nafion Entrapment of a ModelGlucose Biosensor

A. Zabakhsh1

J. Bowers2

A. Querol-Suquia1

R. Steitz3,5

R. Krustev4,5

1 Univ. London, UK2Univ. of Exeter, UK3 MPI-KGF Golm/Potsdam4 TU Berlin5 HMI Berlin

V6 CHE- 04-0620

Biology

152 Study of Lamellar Phases Formedby Nucleoside Functionalized Lipids

P. BaglioniD. BertiE. Fratini

Univ. Florence, IT V1 CHE- 01-1001/

01-0875

153 Peptide-Membrane Interaction R. Willumeit1

J. Andrä2

K. Oetzmann2

F. Förster2

S. Hubo2

M. Kruse2

1 GKSS Geesthacht2 Univ. Hamburg

V1 BIO-01-0998

154 Peptide Membrane Interaction R. Willumeit1

J. Andrä2

K. Ötzmann2

1 GKSS Geesthacht2 Univ. Hamburg

V1 BIO-01-1076

155 Phospholipid Phase TransitionsObserved with an „Excess Water“Cell

J.P. Bradshaw1

T. Harroun1

S. Davis1

Th. Hauss2,3

1 Univ. Edinburgh, UK2 HMI Berlin3 Univ. Düsseldorf

V1 BIO-01-1002

156 Lipid Interactions of ADP-Ribosylation Factor-1’s AmphipathicHelix

S. Davies1

T. Harroun1

J. Bradshaw1

Th. Hauss2,3

1 Univ. Edinburgh, UK2 HMI Berlin3 Univ. Düsseldorf

V1 BIO-01-1078

157 Structural Analysis of H2O andDetergent within PS I Crystals

P. Fromme1

J. Frank1

Th. Gutberlet2

Th. Hauss2,4

S. Dante3

1 TU Berlin2 HMI Berlin3 TU Darmstadt4 Univ. Düsseldorf

V1 BIO-01-1075

158 Interaction of β-Amyloid Peptideswith Lipid Membranes

S. Dante3

T. Hauss2,1

N.A. Dencher3

1 HMI Berlin2 Univ. Düsseldorf3 TU Darmstadt

V1 EF

159 Interhelix Fluctuations inBacteriorhodopsin

W. Doster1

R. Lechner2

Th. Hauss3,2

1 TU München, Garching2 HMI Berlin3 Univ. Düsseldorf

V3 BIO-03-0139

XIX



160 Vibrational Change on LigandBinding to Proteins

J.C. Smith1

J. Pieper2

A. Desmedt2

M. Oettl3

E. Balog1

1 Univ. Heidelberg2 HMI Berlin3 Univ. Waikato, NZ

V3 BIO-03-0156

161 Dynamics of DNA at Different Levelsof Humidity

H. Grimm1

R.E. Lechner2

A. Desmedt2

A. Sokolov3

1 FZ Jülich2 HMI Berlin3 Univ. Akron, Ohio,USA

V3 PHY- 03-0180

162 Density of Phonon States in theLight-Harvesting Complex II ofGreen Plants

J. Pieper1

R.E. Lechner1

A. Desmedt1

K.D. Irrgang2

G. Renger2

1 HMI Berlin2 TU Berlin

V3 EF

163 Report about Characterization ofPEI/DNA-Complexes by SANS

G. Lukowski1

R. Fischer2

A. Hoell3

1 Univ. Greifwald2 Univ. Marburg3 HMI Berlin

V4 BIO- 04-0585/

04-0635

164 Characterization of ProteinConformation along the CatalyticPathway

S. Magazù1

F. Migliardo1

A. Wiedenmann2

A. Hoell2

1 Univ. Messina, IT2 HMI Berlin

V4 MAT- 04-0592

165 A Structural Study of LivingPolymers Formed by SelfAssembling of PLNs

P. Baglioni1

D. Berti1

U. Keiderling2

1 Univ. Florence, IT2 TU Darmstadt

V4 CHE- 04-0593

166 Kinetics of Protein Adsorption onColloids

W.G. Bouwman1

J. Efimova1

M.G.E.G. Bremer1

U. Keiderling2

1 IRI, Delft Univ., NL2 TU Darmstadt

V4 BIO- 04-0597

167 The Nano-Structure ofMagnetosomes Studied by SANS

A. HoellA. Wiedenmann

HMI Berlin V4 EF

168 Effect of Temperature on theAdsorption of Lysozyme on a SilicaSurface

K. Czeslik1

G. Jackler1

R. Steitz2,3

Th. Gutberlet2

1 Univ. Dortmund2 HMI Berlin3 MPI-KGF Golm/Potsdam

V6 CHE- 04-0660

169 Lipid Bilayers Adsorbed to the Solid-Liquid Interface

B. Klösgen1

T. Gutberlet2

R. Steitz2,4

I. Estrela-Lopis2,3

1 FU Berlin2 HMI Berlin3 TU Berlin4 MPI Golm, Potsdam

V6 BIO- 04-0608

04-0663

170 Binding of Aß (25-35) to aSupported Lipid Layer by NeutronReflectometry

S. Dante1

T. Hauß 2,3

T. Gutberlet3

R. Steitz 3,4

1 TU Darmstadt2 Univ. Düsseldorf3 HMI Berlin4 MPI-KGF Golm/Potsdam

V6 EF

171 Investigation of Hydration Effect onthe Lamellar Structure of StratumCorneum

Th. A . Steriotis1

G. Charalampopoulou1

T. Hauss2

1 NCSR Demokritos, GR2 Univ. Düsseldorf

V1 BIO-01-1077

172 A Comparative Study of CrystalStructure of Dinosaur and ResentAnimal Bones

S. Gerbish1

D.M. Többens2

D. Sangaa1

G. Batdemberel3

1 NU Mongolia2 HMI Berlin3 MTU Mongolia

E9 OTH-

01-0994

Material Science and Industrial Applications

175 Determination of Residual Stress byND in 6061Al-15 vol%SiCw

Composites with Different WhiskerOrientation/Distribution

G. Gonzalez-Doncel1

R. Férnandez Serrano1

G. Bruno2

1CENIM, Madrid, E2HMI Berlin

E3 MAT- 01-0741

01-0773

174 Neutron Diffraction Studies ofCrystal Structure of GroundSquirrel’s Bone

D. Sangaa1

H. Fuess2

D.M. Többens3

G. Batdemberel4

1 Nat. Univ. Mongolia, NM2 TU Darmstadt3 HMI Berlin4 MTU, Mongolia

E9 PHY-

01-1063

XX



192 SANS Study of MicrostructuralChanges in Ni-base Superalloy dueto Long-time Thermal Exposure

J. Zrník1

P. Strunz2

P. Hornak1

V. Vrchovinsky1

1TU Kosice, SK2HMI Berlin

V4 MAT- 04-0652

193 SANS Investigation of Magnetic NiCrystals in an Amorphous Ni-P-Alloy

D. Tatchev1,2

A. Hoell31Univ. Rostock2Bulg.Acad.Sc.,Sofia, BG3HMI Berlin

V4 MAT- 04-0583

194 Magnetic Correlation Length InNanocrystalline Fe89Zr7B3Cu1

O. Moze1

K. Suzuki2

J. Cadogan2

E. Agosti1

A. Hoell3

A. Heinemann3

1Univ. Modena, IT2Univ. NS Wales, AU3HMI Berlin

V4 PHY- 04-0648

195 Dissolution and Precipitation of NbCin Fe70Ni30

N.H. van DijkS.E. OffermanS. van der ZwaagJ. Sietsma

TU Delft, NL V4 MAT- 04-0649

196 Structural Phase Transition on Fe-PtAlloys

T.D. Pham1

E. Brück1

A. Hoell2

1Uni Amsterdam, NL2HMI Berlin

V4 PHY- 04-0650

197 H/D-Contrast Variation Combinedwith SANSPOL in Ferrofluids (I):Constituents

A. WiedenmannM. KammelA. Hoell

HMI Berlin V4 EF

198 H/D-Contrast Variation Combinedwith SANSPOL in Ferrofluids (II):Composition

A. WiedenmannA. HoellM. Kammel

HMI Berlin V4 EF

199 SANS Investigations ofBariumhexaferrit Ferrofluids and itsPrecursors

A. Hoell1

A. Wiedenmann1

R. Müller2

1HMI Berlin2IPHT Jena

V4 EF/MAT- 04-

0637

200 Concentration Effect in Co-Ferrofluids: Field InducedCorrelations

A. WiedenmannA. HoellM. Kammel

HMI Berlin V4 EF

201 Concentrated Ferrofluids andPolystyrene Fixed MagnetiteStudied by SANSPOL

A. HoellA. Wiedenmann

HMI Berlin V4 EF

202 Field Induced Ordering in Ferrofluids A. WiedenmannA. HeinemannA. HoellM. Kammel

HMI Berlin V4 EF

203 Time-Resolved In-Situ SANSInvestigation of the SinteringBehavior of Nanocrystalline Y2O3-Doped ZrO2 Ceramics

H. Hahn1

M. Winterer1

U. Keiderling3,2

A. Wiedenmann2

J. Seydel1

1TU Darmstadt2HMI Berlin3TU Darmstadt

V4 EF

204 SANS Investigation of the DynamicSintering Behavior ofNanocrystalline Y2O3-Doped ZrO2

Ceramics with Hugh Time Resolution

H. Hahn1

M. Winterer1

U. Keiderling3,2

A. Wiedenmann2

J. Seydel1

1TU Darmstadt2HMI Berlin3TU Darmstadt

V4 EF

205 Pore Microstructure in CeramicThermal Barrier Coatings

G. Schumacher1

P. Strunz2

R. Vassen3

1BAM Berlin2HMI Berlin3FZ Jülich

V4 MAT- 04-0641

206 Investigation of Cavities inSuperplastically Deformed Y-TZP bySANS

J. Saroun1

P. Strunz2

V. Ryukhtin1

S. Harjo3

Y. Motohashi3

1CAS NPI, CZ2HMI Berlin3Ibaraki Univ., JP

V4 MAT- 04-0645

207 Effect of High-Pressure HydrogenCharging on Austenitic StainlessSteels

S. Danilkin1

M. Hölzel2

D. Többens1

1HMI Berlin2TU Darmstadt

E9 EF

208 Evalutation of IrradiationEmbrittlement of Reactor PressureVessels (RPV)

A. Ulbricht1

P. Strunz21FZ Rossendorf, Dresden2HMI Berlin

V4 MAT- 04-0584

209 A SANS Study of Corax N330 E. Hoinkis HMI Berlin V4 EF

XXII



210 Investigations of Metal Foams J. Banhart1

H. Stanzick1

J. Klenke2

S. Danilkin2

1IFAM, Bremen2HMI Berlin

E1MAT- 02-

0271

212 Redistribution of Ion-ImplantedBoron in the Photoresist S 1813

D. Fink1

M. Behar2

M.F. Soarez2

M. Müller1

1HMI Berlin2UFRGS, Porto Alegre, BZ

B7 EF

Instrument Development

213 Test Measurement with a Refillable3He Filter

A. RuppA. GorzelJ. Klenke

HMI Berlin E1 EF

214 The Use of a Refillable 3He Filter Cellin Small Angle Neutron Scattering

A. WiedenmannA. RuppA. Gorzel

HMI Berlin E1 EF

215 The Use of a Refillable 3He Filter Cellas Neutron Polariser

A. RuppA. GorzelJ. Klenke

HMI Berlin E1 EF

216 Diffraction Study of Synthetic MicaSingle Crystals

H. FritzscheJ. Klenke

HMI Berlin E1 EF

217 Asymmetry Function at AxiallyFocusing Powder Diffractometers

D.M. Többens HMI Berlin E9 EF

218 Test of Spin-Echo Resolved GrazingIncidence Neutron Scattering(SERGIS)

J. Major1

Th. Keller1

S. te Velthuis2

G. Felcher2

1MPI Stuttgart2ANL Argonne USA

V2 PHY- 02-0341 test

219 Spin-Echo Resolved GrazingIncidence Neutron Scattering(SERGIS)

J. Major1

G. Felcher2

S. te Velthuis2

Th. Keller1

1MPI Stuttgart2ANL Argonne USA

V2 PHY- 02-0341

220 Neutron Larmor Diffraction: d-Spacing Spread of PGMonochromators

T. Keller1

K. Habicht2

M.Th. Rekveldt3

1MPI Stuttgart2HMI Berlin3IRI, TU Delft, NL

V2 EF

221 γ-Sensitivity of 3He-Detectors forTime of Flight Measurement

K. Zeitelhack1

G. Montermann2

R. Schneider3,4

R. Gilles3

B. Krimmer3

P. Strunz4

A. Wiedenmann4

1TU München2Mesytec GbR3TU Darmstadt4HMI Berlin

V4 EF

222 An Investigation into thePerformance of the RUDETECDetector

J. Keshaw1

A. Wiedenmann2

Th. Wilpert2

1NECSA South Africa2HMI Berlin

V4 EF

223 Test Measurements on a LinearPosition Sensitive Detector

S. Messoloras1

A. Wiedenmann2

K. Mergia1

Th. Wilpert2

A. Salevris1

1NCSR Demokritos, EL2HMI Berlin

V4 EF

224 Position Sensitive Detector Tests atV4

R. Gilles1

B. Krimmer1

P. Strunz2

A. Wiedenmann2

K. Zeitelhack3

R. Schneider1,2

G. Montermann4

1TU Darmstadt2HMI Berlin3TU München4Mesytec

V4 EF

225 Discriminating between Diffuse &Specular Reflection Using NeutronSpin Echo

M. Fitzsimmons1

J. Major2

R. Pynn1

Th. Rekveldt3

1Los Alamos Nat Lab, USA2MPI, Stuttgart3Univ. Delft, NL

V6 PHY- 04-0667

XXIII



226 Ultra-Small Neutron Deflections bySheets, Gratings and MagneticPrism

A.G. Wagh1

V.C. Rakhecha1

W. Treimer2

1BARC, IN2HMI Berlin

V12b

PHY- 04-0681

227 Refraction Data Based TomographicImaging

W. Treimer1

M. Strobl2

A. Hilger1

H.J. Peschke1

1TFH Berlin2HMI Berlin

V12a

EF

228 Realisation of a DCD with 7- BouncePerfect Crystals

W. Treimer1

M. Strobl2

A. Hilger1


V12b

EF

229 High Resolution Measurements withSeven Bounce Channel Cut Crystals

W. Treimer1

M. Strobl2

A. Hilger1


V12b

EF

230 Edge Effects in a DCD W. Treimer1

M. Strobl2

A. Hilger1


V12b

EF

231 A Tuneable Channel Cut Crystal W. Treimer1

M. Strobl2

A. Hilger1


V12b

EF

232 New Solid State Neutron OpticalElements

T. KristH. Fritzsche

HMI Berlin V14 EF

233 Development on Neutron OpticalElements

T. KristS.-J. ChoJ. Hoffmann

HMI Berlin V14 EF

XXIV

PHY-01-0962 // brandt // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° PHY-01-962

Instrument E1Magnetic structure of DyCo10V2Local Contact J. Klenke, S. Danilkin

Principal Proposer: Y. Janssen, Universiteit van Amsterdam Date(s) of ExperimentExperimental Team: J. Klenke, HMI Berlin

S. Danilkin, HMI Berlin 09/07/2001-16/07/2001

Date of Report: 30/01/2002

The ferrimagnetic pseudobinary system DyCo10V2crystallizes in the tetragonal ThMn12-type structure(space group I4/mmm) with lattice parametersa=8.4 Å and c=4.7 Å. In this structure, theconstituent atoms occupy 4 differentcrystallographic sites: Dy occupies the 2a site, Cooccupies almost fully the 8f site and the 8j site. The8i site is shared randomly by Co and V [1].DyCo10V2 orders ferrimagnetically around TC=466K with the Co and the Dy magnetic momentsantiparallel along the c-axis. At room temperature,the Co-sublattice magnetization is larger than theDy-sublattice magnetization. The spontaneousmagnetization amounts to MS=3 B/f.u. at 300 K.Due to the difference in temperature dependence ofthe magnetic moments, the Dy moments growstrongly at lower temperatures; magneticcompensation occurs at Tcomp=118 K. At a lowertemperature of 41 K, a spin reorientation occurs,where the ordered magnetic moments acquire also aplanar component. This tilting away from the c-axisis temperature dependent, amounting to an angle ofapprox. 13 deg at 5 K. The spin reorientation isascribed to higher-order crystal-field terms for theDy atom [2].Absorption-related difficulties encountered on abar-shaped sample (experiment PHY-01-922),prompted us to cut a small single-crystallinespherical sample of diameter 1.3 mm (~ 9 mg). The experiments were performed on the instrumentE1, used as a two-axis diffractometer. An Orangecryofurnace was used to reach temperatures rangingfrom 5 K to 500 K. The neutron wavelength was2.42 Å.The sample was mounted with the [001]crystallographic direction along the measurementaxis. We collected integrated intensities of 22 to 42(hk0) reflections, of which 11 were independent, attemperatures 5 K, 50 K, 115 K, 300 K and 500 K. Preliminary refinements were made using theCCSL programs. On the basis of a refinement ofdata taken at 500 K (above TC), we verified that thesample crystallizes in the ThMn12-type of structure,with the Co and V atoms sharing the 8i position.Additional intensity was observed on top of the

nuclear refelections, as the temperature waslowered. The magnetic structure at 300 K, 115 K , 50 K and5 K has been refined using the crystallographicparameters and the scaling factor from the 500 Kdata set. The refinements were evaluated accordingto a goodness-of-fit parameter G=√2/N. Theresults are summarized in Table 1. The largerefined thermal displacement factor is probablyrelated to the large absorption cross-section of Dy.The magnetic moments were constrained to bealong the c-axis. Allowing different Co magneticmoments for the different Co-containingcrystallographic sites did not improve thegoodness-of-fit. Therefore, one single Co magneticmoment was used for these sites. At and below 115K, the Co magnetic moment was fixed because itdid not vary significantly anymore. The refinementof the 5 K data set, taken below the spin-reorientation temperature, did not improve when weallowed a tilt angle with the c-axis for the magneticmoments. T 300 K 115 K 50 K 5 KMDy(B/Dy) -2.56(11) -6.69(10) -8.07(16) -8.42(19)MCo(B/Co) 0.79(4) 1.1 1.1 1.1Bov (A2) 6.55(8) 5.96(13) 5.87(21) 5.71(27)RwpG

1.9 %0.28

3.1 %0.67

4.9 %1.03

5.1 %1.50

Table 1: Magnetic moments determined by neutrondiffraction at 300 K, 115 K, 50 K and 5 K.

The different temperature dependence of the Coand Dy magnetic sublattices is in agreement withexpectation. However, it appears that the refined Comagnetic moment is systematically too large. At115 K, near the compensation temperature therefined Co-sublattice magnetic moment (10x1.1=11B) is much larger than the refined Dy magneticmoment (-6.69 B). The refined Dy magneticmoment appears to be in agreement with bulkmagnetic measurements and theoretical predictions.

Currently, a closer look at the diffraction data isbeing carried out. [1] O. Moze et al., J. Alloys Compds. 196 (1993),L1[2] C. Zhang et al., J. Appl. Phys. 83 (1998), 6776

1


EXPERIMENTAL REPORT Proposal N° PHY-02-273Instrument E1Magnetic field induced ordering in the frustrated

antiferromagnet: Gadolinium Gallium Garnet Local Contact J. Klenke

Principal Proposer: O. Petrenko, Univ. of Warwick Date(s) of ExperimentExperimental Team: O. Petrenko, Univ. of Warwick

J. Klenke, BENSCP. Smeibidl, BENSC

11-22.12.00

Date of Report: 10.01.02

In Gadolinium Gallium Garnet (GGG) theantiferromagnetically interacting Gd ions arelocated on two corner-sharing triangularsublattices. The magnetic system is thereforehighly frustrated and does not order in zerofield. AF order can only be induced by theapplication of an external magnetic field. Wehave measured the magnetic diffractionpattern of a single crystal of GGG attemperatures between 50 mK and 0.9 K infields of up to 4 T. The experiment reveals thatthe H-T phase diagram has a much morecomplicated nature than previously assumed. The measurements were carried out usingthe E1 triple axis spectrometer in a double-axis mode, with a PG (002) monochromatorproviding a wavelength of 2.41 Å. A PG filterwas installed in the incident beam to removehigher order contamination. The horizontalcollimation was 40'-80'-40'. The scatteringplane contained the (hk0) reflections so that anexternal magnetic field provided by a verticalsplit-pair cryomagnet was applied along the[001] direction. In order to minimise neutronabsorption we have prepared a sample with99.98% of the non-absorbing isotope, 160Gd,supplied by Oak Ridge National Laboratory.The single crystal sample was then grown atWarwick by the floating zone method. Before applying a magnetic field, we haveattempted to find the magnetic Bragg peaksassociated with the “spin freezing” in zero field.These peaks have been found in a powderdiffraction pattern at temperatures below 140mK and incommensurate positions, such asQ1=0.64 Å-1 and Q2=0.85 Å-1 and severalothers. Our attempts to find single crystalpeaks of the (hk0) type with a scattering vectorlength equal to Q1 or Q2 were unsuccessful. On application of an external field two sets ofmagnetic Bragg peaks appeared,ferromagnetic and antiferromagnetic. Theformer have intensity increasing with the fieldand saturate at higher fields, the latter haveintensity growing in low fields, reaching amaximum, and then decreasing and almost

disappearing at a field above 2.5 T. Fig. 1shows the evolution of the integrated intensityof the three different magnetic peaks at T=60mK with applied magnetic field. The stronger AF peaks, such as (200), havemaximum intensity in a field of about HLOW0.6T, which corresponds to the lower-field phaseboundary on the H-T phase diagram. Thesame field is marked by the start of intensityrising for the weaker AF peaks, such as (330),and for all the FM peaks. The weaker AFpeaks have maximum intensity in a field ofabout HHIGH1.5 T, which corresponds to anupper-field phase boundary. Note the nonzerointensity of the AF peaks in fields well aboveHHIGH. The FM peaks demonstrate a significantvariation of intensity only in the region betweenHLOW and HHIGH. Interestingly, the width of the (200) peak islimited by the instrumental resolution only in asmall region of fields around HLOW. The widthof the weaker AF peaks always seem toremain above the resolution limit. Thisobservation suggests that the true long rangemagnetic order in GGG is induced only in thevicinity of the lower-field phase boundary,while the region of field between HLOW andHHIGH corresponds to an enhancement of theshort range AF order.

Figure 1. Field dependence of the integrated intensity ofthe magnetic peaks in GGG at T=60 mK, H // [001].

2

EXPERIMENTAL REPORT Proposal N° PHY-02-285Instrument E1Magnetic structure of Laves Phases:

Superlattices in a magnetic field Local Contact Jens Klenke

Principal Proposer: RA Cowley, Oxford University Date(s) of ExperimentExperimental Team: MJ Bentall, W Lohstroh

Oxford University 1.11. - 11.11.2001


Superlattice samples that combine a magnetically hardand a soft material show an exchange spring behaviourin applied magnetic fields. DyFe2/YFe2 superlatticesconsist of such a material combination, and the forma-tion of exchange springs can be indirectly deducedfrom magnetisation measurements [1]. In the DyFe2sublayers the Dy ions and the Fe ions are both magneticand the magnetism is determined by the large moments(10B/Dy-atom) and the anisotropy of the Dy whereasthe weaker Fe moment is antiferromagnetically coupledto the rare earth ions. Hence in the investigatedsuperlattice the YFe2 magnetisation is antiparallel tothe net moment of the DyFe2 layers due to the directFe-Fe exchange at the interfaces. However, in largeapplied fields (above a critical bending field HB) theZeeman energy might overcome the exchange and partsof the YFe2 rotates toward the direction of the appliedfield and thus an exchange spring is created. We investigated a superlattice [DyFe2 150Å/YFe2100Å]x50. The sample has been grown by MBE on aNb/sapphire substrate. x-ray diffraction data confirmepitaxial growth and a good layered structure. Frommagnetisation measurements the bending field wasmeasured to be 3T. We measured the scattered intensityin the vicinity of the (220), (111) (113) and (004)Bragg reflections. Due to the C15 crystal structure ofboth DyFe2 and YFe2 the scattered intensity around(220) solely results from the rare earth sublatticewhereas the structure factor of (111) (113) and (004)contains contributions from the rare earth and the tran-sition metal sublattice, respectively. Two sets ofmeasurements have been taken: (i) an applied field of4T and (ii) after the field had been lowered to 0.5T (allmeasurements at 150K) .The field had been appliedalong the [001] easy axis of magnetisation in the layerplane. Fig. 1 shows the scans around (004), where thescan direction was along [110] that is the growth direc-tion of the superlattice. The satellite reflections in thevicinity of the main Bragg reflections result from theartificial bilayer structure of the sample and confirm thecoherent growth over many bilayer repeats. Since onlythe part of the magnetisation perpendicular to the scat-tering vector contributes to the magnetic cross sectionall magnetic scattering around [004] stems frommagnetic moments that are not

Fig. 1: Scan around the (004) reflection of a super-lattice [DyFe2 150Å/YFe2 100Å]x50 in a magnetic fieldof 4T and 0.5T along [001]. The change in scatteredintensity results from components of the magnetisationthat are not collinear to [001] and thus shows the for-mation of an exchange spring.

collinear with the applied field. Comparison of the twodata sets shows a diminishing magnetic contribution asthe field is lowered from 4T to 0.5T. The data arehence consistent with an exchange spring at 4T thatunwinds itself as soon as the field is lower that thebending field HB such that the magnetic structure inlow applied fields is collinear with [001].

[1] M. Sawicki et al, Phys. Rev. B 62 (2000) 5817

-0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10

50

100

150

200

250

300

350

400

4T 0.5T

(004)

T = 150K

SL1003:[DyFe2 150Å/YFe

2 100Å]x50

Cou

nts

H along [1 1 0] [Å-1]

3


EXPERIMENTAL REPORT Proposal N° PHY-02-286/E1

Instrument E1Long range magnetic order inintermediate valence CeLu alloys Local Contact J Klenke

Principal Proposer: Jon Goff, University of Liverpool Date(s) of ExperimentExperimental Team: Pascale Deen

Adina Toader 26 Feb – 11 March ‘01

Date of Report: 25 Feb 2002

Presented at the European Conference onNeutron Scattering, Munich, September 2001

Published in Applied Physics (in press)

Abstract

The magnetic ordering in CeLu alloys hasbeen studied using neutron diffraction and theelectronic state of the Ce has been determinedusing x-ray magnetic resonant scattering(XMRS). CeLu orders with the same magneticstructure as CeY but the temperaturedependence of the order parameter is differentand the average saturated moments on the Cesites is lower. The diffuse neutron magneticscattering observed in other Ce alloys is notobserved for CeLu and this implies that thisunusual scattering originates from thecompetition between the exchange and thedipolar interaction. The XMRS results showthat the Ce in CeLu alloys has an intermediatevalence, and the results suggest that thisbehaviour is due to chemical pressure.

4

EXPERIMENTAL REPORT

ErNi2B2C Interaction between Superconductivity

and Magnetism

Proposal NÆPHY-02-289

Instrument E1

Local Contact

J. Klenke

Date(s) of Experiment

7. 5. - 14. 5. 2001

Principal Proposer: Katrine Nrgaard Toft, Ris National Laboratory

Experimental Team: A.B. Abrahamsen, Ris National Laboratory

P. Smeibidl, Hahn-Meitner Institut

S. Kausche, Hahn-Meitner Institut

Date of Report29. 1. 2002

Several of the rare earth magnetic borocar-

bides show coexistence of superconductivity and

magnetism, and several examples have been seen

of a direct in uence of magnetism on supercon-

ductivity, eg. a suppression of the upper crit-

ical eld for superconductivity is observed for

ErNi2B2C and HoNi2B2C when entering an or-

dered magnetic phase. We present the rst ex-

ample of an experiment showing that a change in

superconducting parameters induces an abrupt

change of the magnetic structure.

Experiment and Results

ErNi2B2C becomes superconducting at 11 K,

and orders magnetically at 6.8 K. The zero eld

magnetic phase is a transverse spin density wave

with an ordering vector of ~Q = (0:55; 0; 0), and

the magnetic moments pointing in the (010) di-

rection. In this experiment we have examined

the magnetic structure when applying a mag-

netic eld in the ab-plane of the crystal. Figure

1 shows longitudinal scans through the magnetic

peak at (0:55; 0; 0) in increasing magnetic eld,

applied along (110). Notice two things from this

plot. First of all, the intensity is suppressed at

16 kOe, and second of all, the period of the mag-

netic structure shifts from 0.55 to 0.57 above 10

kOe, changes to 0.58 at 16 kOe, and goes back

to 0.57 above 17 kOe.

When applying the magnetic eld along (100),

the sharp dip in intensity is replaced by a

plateau, but the position shifts in the same man-

ner as for the eld along (110), and thus one can

identify the eld for which the suppression takes

place either by a minimum in intensity or by a

shift of position. This has been done for both

eld directions and the result is plotted in g-

ure 2 as a function of temperature. The upper

critical eld for superconductivity is also plotted

0.52 0.54 0.56 0.58 0.610

1

102

103

104

[h00]

Cou

nts

in 2

5 se

c.

0 kOe 12 kOe15 kOe16 kOe19 kOe21 kOe

0 5 10 15 20 250

20

40

60

80

Magnetic field in (110) direction [kOe]

Inte

grat

ed in

tens

ity [a

rb. u

nits

]

0 5 10 15 20 250.55

0.56

0.57

0.58

0.59

Magnetic field in (110) direction [kOe]

Pos

ition

of +

QA p

eak

[rlu

]

Figure 1: Left: Scans through +QA (0.55,0,0)

(T = 1:9 K, Hk[110], (h00) scans). Right: Inte-

grated intensity and position of the +QA peak

in increasing eld.

for both eld directions and there is a striking

connection between the two.

T (K)

[100]

[110]

[001]

H(k

Oe)

c2

Figure 2: Hc2 data from Budko et al. PRB 61

R14932, Hk (100): solid circles, Hk (110): open

circles, Hk (001): open triangles. The magnetic

intensity jumps are marked with full circles (Hk(110)) and open diamonds (Hk (100)).

The reentrant behaviour and change of the

ordering vector around Hc2 without obvious

anomalies in Hc2 indicate an unusual strong im-

pact of superconductivity on magnetism.

5

ef_55 // brandt // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EFInstrument E1Study of the magnetic phases of CsCuCl3

for in-plane fields up to 17 Tesla Local Contact *

Principal Proposer: Norbert Stüßer, HMI Date(s) of ExperimentExperimental Team: Andreas Hoser, HMI

Ursula Schotte, HMI *19.3.-25.3.2001


CsCuCl3 is a hexagonal perovskite whichundergoes a structural phase transition at 423 Kdue to the cooperative Jahn-Teller effect fromthe Cu2+ ion. The lattice symmetry changesfrom P63/mmc to P6122 in the low temperaturephase. The lattice consists of chains of facesharing distorted Cl6-octahedra centered by theCu2+ ions along the c axis. These chains arearranged on a triangular lattice in the ab plane.Long-range magnetic order of theCu2+ moments occurs below 10.65 K. Atriangular spin arrangement of the 120°-typestructure is formed in the ab plane and anincommensurate spiral along the c axis with arepetition length of about 71 layers.

magnetic structure

Neutron diffraction has been performed tostudy the magnetization process of CsCuCl3with the magnetic field aligned within the abplane. The magnetic phase diagram wasinvestigated from 2 K up to TN in fields up to17 Tesla. The phase line for the expected

incommensurate-commensurate (IC-C) phasetransition could be determined throughout thewhole phase diagram. At low temperature theIC-C transition is roughly at half the saturationfield HS. The neutron diffraction pattern werefound to be well described by a sinusoidallymodulated spiral in fields up to 1/3 HS. Theinitial increase of the scattering intensity inrising field points to a continuous reduction ofthe spin frustration on the triangular lattice.Between 1/3 HS and 1/2 HS there is a newphase IC1΄ where the spiral vector has aplateau in its field dependence. Close to theIC1΄-C transition a growing asymmetry ofmagnetic satellite-peak intensities points todomain effects which are related to the liftingof the chiral degeneracy in the ab plane inrising field. The phase diagram obtained hassome similarities with those calculated forstacked triangular-lattice antiferromagnetsconsidering the effects of quantum and thermalfluctuations.

phase diagram

a

b

a

c

b

6

EXPERIMENTAL REPORT

Rare earth induced phase transition at HoMnO3

Proposal NÆ01-068

Instrument E2

Local Contact

D. Hohlwein1; 2


16.01.-21.01.2001,

07.05.-08.05.2001

Principal Proposer: W. Prandl1, 1Institut fur Kristallographie,

Experimental Team: Th. Lonkai1, Universitat Tubingen

D. Hohlwein1;2, 2Hahn-Meitner Institut, Berlin

[email protected]

Date of Report19.01.2002

The determination of the magnetic space

groups of multiferroic hexagonal RMnO3 com-

pounds (R 2 fEr;Ho; In;Lu;Sc;Tm;Y;Ybg)

seemed to be unsolvable for more than 30 years

[1] - the nuclear position of Mn near (1=3; 0; 0)

made the distinction of magnetic space groups

with time inversion of the 63 axis (P60

3cm0,

P60

3, P60

3c0m) and of space groups without time

inversion of the 63 axis (P63c0m0, P63, P63cm)

nearly impossible. Only in recent years the

development of second harmonic spectroscopy

as a tool of magnetic structure determination

[2] and the use of new techniques of renement

[3] solved this problem.

To determine the in uence of rare earth or-

dering on the structure we performed neutron

powder measurements ( = 2:4A) at the at

cone diractometer E2 on HoMnO3 samples in

a temperature range T 2 [1:5K; 35K] around

the rare earth ordering temperature at T = 5K

(Fig.1). The renement (Fig.2) shows a slow

increase of the magnetization of the Ho lattice

with decreasing temperature, which can be

explained by two Brillouin functions (master

slave process due to Mn lattice) and a sharp

increase of the magnetization at T 5K

(Ho ordering). The ordering of the Ho lattice

leads to a magnetic phase transition P60

3cm0

(T > 5K) ! P63cm [3]. This is accompanied

by an increase of the cell volume at T 5K

and a magnetostrictive decrease at lower tem-

peratures.

[1] E. F. Bertaut andM. Mercier, Phys. Lett.5,

27-9 (1963)

[2] M. Fiebig et al., Phys. Rev. Lett. 84,

5620-5623 (2000)

[3] Th. Lonkai, Appl. Phys. A (2001) in press

0 10 20 30 40 50 60 70 80 9010

20

30

40

50

60

70

80

90

0

500

1000

1500

2000

2500

3000

3500

4000

Cp [J/(mol K)]

Cp/T [J/(mol K2)]

Cp/

T [J

/(m

ol K

2 )]

temperature [K]

Cp

[J

/(m

ol K

)]

Figure 1: Specic heat data reveals the ordering

temperature of Ho at T 5K.

0 10 20 30 40 50 60 70 80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 10 20 30 40 50 60 70 80

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

par

amag

net

ic

P6 3'

P6 3'c

'm

P6 3c

m

P6 3'c

m'

µ [µ

B]

temperature [K]

par

amag

net

ic

P6 3'

P6 3'c

'm

P6 3c

m

P6 3'c

m'

µ(Ho)

µ [µ

B]

temperature [K]

Figure 2: Magnetization of the Ho lattice.

0 10 20 30 40 50 60 70 80368.4

368.6

368.8

369.0

369.2

369.4

par

amag

net

ic

P6 3'c

m'

P6 3

P6 3'c

m'

P6 3c

m

cellv

olum

e [(

10-1

0 m)3 ]

temperatures [K]

Figure 3: The cell volume shows a sharp increase

at the ordering temperature of Ho, followed by a

magnetostrictive decrease.

7

EXPERIMENTAL REPORT

2D ordering in YMnO3

Proposal NÆ01-068

Instrument E2

Local Contact

D. Hohlwein1; 2


09.05.-14.05.2001




[email protected]


A3+1xB

3+xMnO3 perovskite structures are

built of three dimensionally connected MnO6

octahedra. Thus, the magnetic structure of

the compounds results basically of a compe-

tition of the ferromagnetic double exchange

(Mn3+O2Mn4+) and the antiferromag-

netic super exchange (Mn3+O2Mn3+,

Mn4+O2Mn4+). With changing x this can

lead to the well known complex phase diagrams

of the perovskites, e.g. [1].

In contrast to the 3D perovskites, the

hexagonal manganites RMnO3 (R 2

fEr;Ho; In;Lu;Sc;Tm;Y;Ybg) are built of

planes of two dimensionally connected MnO5

bipyramids, rotated by 60Æ in respect to

each other, separated by R planes, generat-

ing Mn3+ O2 O2

Mn3+ inter plane

exchange paths (super super exchange) and

Mn3+ O2 Mn3+ in plane exchange paths

(super exchange) [2].

To observe the forming of the 120Æ arrangement

of the Mn-spins [3,4], we performed neutron

single crystal measurements ( = 2:4A) on a

YMnO3 single crystal, h0l plane, near the Neel

temperature TN 67K.

The data (Fig.1) shows clear evidence of 2D

ordering above the Neel Temperature in the

ab plane. A mean eld calculation (not shown

here) resulted in a strong negative in plane

exchange and no evident inter plane exchange.

The 2D ordering can be followed up to 170K

(Fig.2).

[1] E. O. Wollan, W. C. Koehler,

Phys. Rev. 100, 545 (1955)

[2] E. F. Bertaut, Phys. Lett. 5, 27 (1963)

[3] M. Fiebig et al., Phys. Rev. Lett. 84,

5620-5623 (2000)


Figure 1: YMnO3, (h0l) plane, h vertical, k hor-

izontal. Streaks parallel to the h-axis show clear

evidence of 2D ordering.

15 20 25 30 35 40

0

2

4

6

8

10

12

72 K

170 K

2Θ

tem

p. [a

.u.]

cts

[a.u

.]

Figure 2: Up to T = 170K intensity of the

streaks can observed revealing 2D short range or-

der. (Smoothed data.)

8

EXPERIMENTAL REPORT

Single crystal studies on HoMnO3

Proposal NÆ01-068

Instrument E2

Local Contact

D. Hohlwein1; 2


04.09.-09.09.2001




[email protected]


Due to the identical ionic radii of Ho and Y

HoMnO3 and YMnO3 build an ideal system

to study rare earth in uence on Mn ordering.

In recent studies we found a magnetic phase

transition at T 5K in HoMnO3 due to rare

earth ordering [1,2]. In order to deepen the

understanding of the role of the rare earth

ion Ho in the ordering process, we performed

neutron single crystal measurements ( = 2:4A)

in a temperature range of 1:5K < T < 40K and

near the Neel temperature TN 75K.

Similar to YMnO3 [3] we found 2D ordering in

HoMnO3 above the Neel temperature (Fig.1).

The moments form a 120Æ arrangement similar

to YMnO3.

With increasing Ho moment, (001) grows

(Fig.2a), which gives evidence for an out of

plane moment of the Mn lattice, possibly due

to a Dzyaloshinskii-Moriya interaction.

(301) (Fig.2b) shows an increase of intensity

with decreasing temperature due to the increas-

ing Ho moment in the (2a) position (0,0,z), and

a sudden decrease at the ordering temperature

of 5K, due to the fact, that rare earth ordering

in (2a) in P63cm is forbidden. The sudden

increase of (301) at lower temperatures again

shows a reordering in the rare earth position

(2a), giving an explanation for the magne-

tostrictive eect at 5K [2]. Obviously, the

magnetic symmetry has to be reduced to P31m

to explain the data.


[2] Th. Lonkai, BENSC experimental reports,

rare earth induced phase transition at HoMnO3

[3] Th. Lonkai, BENSC experimental reports,

2D ordering in YMnO3

Figure 1: HoMnO3, (h0l) plane, h vertical, k

horizontal. Streaks parallel to the h-axis give

clear evidence for 2D ordering.

0 5 10 15 20 25 30 35 40750

000

250

500

750

000

250

500

750

000

temperature [K]

(a) (001)

0 5 10 15 20 25 30 35 400

125

250

375

500

625

750

875

temperature [K]

(b) (301)

Figure 2: Both peaks (001) and (301) give evi-

dence for a reduction of the magnetic symmetry

to P31m.

9



Instrument E2*Detailed Investigation of the Crystalline andMagnetic Structure of Dy0.5Tb0.5Cu2 Local Contact

R. Schneider

Principal Proposer: Astrid Schneidewind, TU Dresden, IAPD Date(s) of ExperimentExperimental Team: Roland Schedler, TU Dresden, IAPD

Ulrike Witte, TU Dresden, IAPD 22. - 31. 01.2001

Date of Report: 20. 01. 2002

IntroductionRCu2 compounds crystallizing in the ortho-rhombic CeCu2 structure are investigatedbecause of the large variety of magneticphenomena. TbCu2 and DyCu2 show relatedmagnetic structures with different temp-eratures of magnetic phase transitions.Both compounds are found to undergo amagnetic axis conversion in high magneticfields [1]. The converted state reconvertsin zero field at about 100 K [2]. By in-vestigating the temperature and fielddepending magnetization it was shown thatthe converted state occurs also inTb0.5Dy0.5Cu2 and is stable at room tempe-rature for some hours [3]. Two magneticphase transitions are observed at TN = 39K and T’= 25 K in zero field. The momentsare assumed to be parallel to the crystal-line a-axis. The E2 experiment is per-formed to determine the crystalline andmagnetic structure of Tb0.5Dy0.5Cu2 tounderstand the pinning of the convertedstructure.

Experiment and ResultsThe Tb0.5Dy0.5Cu2 experiment is performed ona single crystal of about 2 x 2 x 2 mm3.The crystalline structure is determined inthe ac-scattering plane (k = 0) at 300 K,36.4 K and 28.8 K (wave length = 2.39Å). Using the flat cone mode the ac-planeswith k = 0.1, 0.2 0.3, 0.4, 1 are studiedat T = 1.5 K. No deviation from the CeCu2structure and no additional magneticreflections are observed compared to TbCu2within the experimental error. The sampleincludes additional crystals with agrowing direction turned around thecrystalline b-direction of the main crystal.

The magnetic structure is further studiedat = 1.21 Å in the bc-scattering planewith h = 0 and h = 1/3 at T = 1.5 K and inmagnetic fields along the crystalline a-axis of 0H 2.5 T. In zero fieldmagnetic reflections are observedconsistently to the magnetic TbCu2structure. The magnetic field dependenceof the magnetic intensity is shown inFig.1 at the (011)+ reflection with = (1/3 0 0). Observing the fielddependence in more detail a step-wisephase transition is observed. So themagnetic structure of Tb0.5Dy0.5Cu2 seems to

Fig.1: Intensity depending on the magneticfield.

164 165 166 167 168 169 1700

200

400

600

T = 1.5 K

(0 1 1) +

Inte

nsity

H = 2.00 T H = 1.80 T H = 1.70 T H = 1.67 T H = 1.30 T H = 0.00 T

be the same as observed at lowtemperatures in TbCu2 and DyCu2. Applyingmagnetic fields along a an additionalmetamagnetic phase transition may occur atabout 0H = 1.7 T which is not observed inTbCu2 or DyCu2 (see Fig.2). This would bein consistence with the resultsmagnetization measurements.

Fig.2: Integrated Intensity of Phi-scansdepending on the magnetic field.

1.4 1.6 1.8 2.0

1000

1500

2000

2500

3000

0.0 0.5 1.0 1.5 2.0 2.50

1000

2000

3000

0H[T]

E2: Tb0.5Dy0.5Cu2 (0 1 1) + reflection at T = 1.5 K

Inte

grat

ed in

tens

ity

0H [T]

References[1] M. Loewenhaupt et al. Physica B246-247(1998) 472-475. [2] P. Svoboda et al. Europhys. Lett. 48(1999) 410. [3] M. Loewenhaupt et al., BrazilienJournal of Physics 30 (2000) 754.

10


T (K)1 2 3 4 5 6 7

B int

(T)

0.0

0.1

0.2

0.3

0.4

0.5(5/8 0 0) AF1(0.633 0 0.02) AF2(0.618 0 0) AF3(0.64 0 0)SW AF4(0.655 0 0) FM1(0.65 0 0.03) FM2(0.65 0 0) FM3(0.65 0 0.02)SW FM4

TmCu2

PAF1

AF2

AF3 AF4

FM4

FM3

FM2FM1

B || b


Instrument E2Details of Magnetic Phase Diagram of TmCu2Single Crystal Local Contact

R. Schneider

Principal Proposer: Svoboda Pavel Charles Univ., Prague Date(s) of ExperimentExperimental Team: Vejpravová Jana Charles Univ., Prague

26.2. – 11.3. 2001

Date of Report: 14.3. 2001

The series of orthorhombic intermetallic compoundsRCu2 (R = rare earth metal) has attracted new attentionwithin last years and is systematically investigatednamely due to their unusual magnetoelastic behavior –the so-called conversion of the Ising axis in highmagnetic fields [1]. Recently, we succeeded to grow newhigh-quality single crystal of TmCu2 by Czochralskipulling technique and besides the bulk studies, thedetailed microscopic study of the magnetic phasediagram was highly desirable. Already from the firstneutron diffraction experiment on E6 diffractometer inSeptember 2000 we found that the magnetic phasediagram is extremely complex [2] and we were able todescribe just several of the observed phases. To clarifythe situation we have performed a detailed diffractionexperiment on E2 diffractometer using VM3 verticalcryomagnet. The sample was mounted in the a-cscattering plane as b-axis is the easy axis ofmagnetization. In this experiment we have fully utilizedthe unique characteristics of E2, namely the 80º detectorand good resolution in the scattering plane.TmCu2 orders antiferromagnetically (AF) at TN = 6.5Kand two additional order-to-order phase transitions weredetected from the bulk measurements at 4.3K and 3.3Kin zero magnetic field [3,4]. Magnetization curves alongthe b-axis show several step-like metamagnetictransitions [3]. The existence of at least three differentmagnetic phases in zero magnetic field was alreadyconfirmed from the E6 experiment. From the detailed experiment in vertical magnetic fieldwe were able to deduce the magnetic phase diagrampresented on Fig. 1.

Fig. 1: Magnetic phase diagram of TmCu2 in B||b axis.The overlap of phases demonstrates the first-order phasetransitions.

The ground-state phase AF1 corresponds to the squared-up magnetic structure with magnetic moment parallel tothe b-axis, consisting of ferromagnetic b-c planesantiferromagnetically stacked along the a-axis withmagnetic unit cell 8a x b x c and characterized by apropagation vector 01 = (5/8 0 0).

Fig. 2: The diffraction pattern of the ground-state phaseAF1 in the h-l scattering plane. N denotes nuclearreflections, numbers show the corresponding harmonicsof the propagation vector (for l = -1, 0 and 1).

The phase just below TN is described by incommensuratespin wave with the propagation vector (0.65 0 0). Fromthe other diffraction patterns we may conclude, that allthe other phases are formed as a derivatives of the abovementioned with some kind of ‘spin-slip’ behavior.Finally, above the FM4 phase, there is field-inducedferromagnetic phase – propagation (0 0 0).The only remaining uncertainty in this phase diagram isthe possible propagation along the b-axis, which wewere not able to study in the present experimentalgeometry. To clarify that we plan another experimentusing the horizontal cryomagnet.References:[1] P. Svoboda et al., Europhysics Letters 48 (1999) 410[2] P. Svoboda et al., Exp. Report on PHY-01-913, HMI[3] Z. Smetana et al., J.Phys.F: Met.Phys. 16 (1986) L201[4] P. Svoboda et al., phys. stat.sol. (a) 111 (1989) 285

11


EXPERIMENTAL REPORT Proposal N° PHY-01-948Instrument E2/E9A neutron diffraction study of the transition from the

spin-gap to magnetic long-range order in the PbNi2-

xAxV2O8 (A=Mg, Co) materials. Local Contact R.Schneider, D.Többens

Principal Proposer: A. Lappas, FORTH/IESL, 711 10 Heraklion, Greece Date(s) of ExperimentExperimental Team: I. Mastoraki, J. Giapintzakis, A. Lappas, FORTH/IESL

D. Többens, HMIR. Schneider, J-U. Hoffmann, HMI

20. 6 – 24. 6. 2001


The undoped PbNi2V2O8 compound [1] has been widelystudied as a model lower-dimensional system whichexhibits a Haldane gap in its magnetic excitationspectrum [2]. A very interesting physical phenomenon insuch a system is the spin-vacancy-induced magneticordering [3] occuring by substitution of the Ni2+ (S=1)ions from Mg2+ (S=0) ions [2]. In this work we study themicroscopic magnetic properties of the quasi-onedimensional PbNi2-xAxV2O8 (A=Mg or Co) solids byboth high-intensity (E2; λ=2.398 Å) and high-resolution(E9; λ=2.398 Å) neutron powder diffraction. We havealready found, with bulk susceptibility measurements,that these materials are magnetically ordered atsignificantly different temperatures, i.e. exhibit amaximum ordering temperature of ~3.5 K for Mg-doping of x=0.16 and ~9 K for a similar Co content.From the present experiments we extracted furtherinformation regarding the type of the magnetic orderingin two extreme cases, namely: when non-magnetic Mg2+

(S=0) or magnetic Co2+ (S=3/2) ions substite the S=1 Nisites. We determined the underlined magnetic structuresand the fact that Néel type of transitions do take placefor two members: the PbNi1.88Mg0.12V2O8 (TN~3.4 K)and the PbNi1.92Co0.08V2O8 (TN~7.2 K). Rietveld analysisof the difference plot (Fig. 1), produced from patternsabove and below TN, indicates that the magnetic unit cellconsists of 16 Ni2+ ions, arranged along four 4-foldscrew axes, with the nearest neighbour Ni momentscoupled antiferromagnetically (AF) both along the c-axisand in the ab plane (=[000]) (Right panel: Fig. 2). Thespin configuration is such as that the magnetic momentsare parallel to the c-axis [4]. To investigate whether theNéel ordering is accompanied by structural phasechanges, we also collected high-resolution E9 data at300 and 2 K for PbNi1.88Mg0.12V2O8 (Fig. 3). We findthat it remains tetragonal down to 2 K and it isisostructural to the parent SrNi2V2O8 [1]. However, localdistortions of the VO4 tetrahedra, separating the NiO6chains along the c-axis, result in shorter Ni-Ni interchaindistances that may enhance the out-of-chain magneticexchange coupling and lead to 3D AF ordering.

[1] R. Wichmann and Hk. Müller-Buschbaum, Rev. Chim.Miner 23, 1 (1986).[2] Y. Uchiyama, Y. Sasago, I. Tsukada, K. Uchinokura, A.Zheludev, T. Hayashi, N. Miura, P. Boni, Phys. Rev. Lett. 83,632 (1999).[3] E. F. Shender and S. Kivelson, Phys. Rev. Lett. 66, 2384(1991).[4] I. Mastoraki, A. Lappas, R. Schneider, and J. Giapintzakis,(ICNS 2001) Appl. Phys. A, in press.

Fig. 1. Rietveld analysis of the purely magneticdiffraction pattern (E2) for PbNi1.92Co0.08V2O8, obtainedby subtraction of the 12 K profile from that at 1.6 K.

0 1 2 30

50100150200250300

<>1.6 K=0.87(5) B

=0.27(3)

(031

) M P

eak

Cou

nts

(a.u

.)

Temperature (K)

Fig. 2. Left: Evolution of the strongest AF Bragg peakfor PbNi1.88Mg0.12V2O8. With TN~3.4 K, we find acritical exponent appropriate for 3D magnets. Right:One unit-cell and the AF spin configuration in PbNi2-

xAxV2O8 solids – ‘white’ and ‘black’ circles representspins ‘up’ and ‘down’ with respect to the c-axis.

Fig. 3. Observed, calculated and difference Rietveldplots of a high-resolution diffraction pattern (E9) forPbNi1.88Mg0.12V2O8 at 2 K.

cba

20 40 60 80 100 120 140-4000

-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

Rwp: 10.2 %

2: 2.92 T= 2 Ka=b=12.2243(1), c=8.3455(1)S.G. I41cd

Inte

nsity

(a.u

.)

2 (deg)

10 20 30 40 50 60-300

-200

-100

0

100

200

300

400 <>=0.97(6) BRwp: 88.3%

2: 13.8

(0 1

3) M

(3 2

1) M

(0 3

1) M

(2 2

0) M

(2 1

1) M

(0 1

1) M

(0 0

1) M

(1 1

0) M

(1 0

0) M

NuclearM

Inte

nsity

(a.u

.)

2è (deg)

12


EXPERIMENTAL REPORT Proposal N° PHY-01-949Instrument E2Modulated magnetic Structure in CaCuxMn7-xO12

with Magnetic Field Local Contact R. Schneider

Principal Proposer: R. Przenioslo, Warsaw University, Poland Date(s) of ExperimentExperimental Team: M. Regulski, I. Sosnowska,

Warsaw University, PolandR. Schneider, HMI / Universität Tübingen

11-16/06/2001


AbstractThe crystal and magnetic structures of theCaCuxMn7-xO12 compounds with (x=0.3) and(x=0.7) were investigated by X-ray and neutronpowder diffraction. The crystal structureparameters of the (x=0.3) compound at 60 Khave been refined within the trigonal spacegroup R-3. The magnetic moments of Mn ionsin the (x=0.3) sample become ordered below40 K. The magnetic ordreing is modulated witha propagation vector (0,0,). A model of themagnetic structure which is in agreement withthe experimental data is proposed along withan estimation of the temperature dependenceof the magnetic moments value. The magneticordering has a reduced correlation length ofabout 250 Å. The (x=0.7) compound do notshow any long range magnetic ordering downto 1.5 K.

Neutron powder diffraction measurements ofCaCuxMn7-xO12 (x=0.3) have been performedbetween 60 K and 1.5 K by using neutronwavelength =2.41 Å. The nuclear diffractionpeaks can be described by using the trigonalstructural model [1]. The low temperatureneutron diffraction patterns of CaCuxMn7-xO12contain several magnetic diffraction peakswhich vanish between 40 K and 45 K.

A model of magnetic ordering already bservedin CaMn7O12 [2] has been taken into account.The Mn ions located in the (9d), (9e) and (3b)sublattices are arranged in horizontal planes.The Mn ions lying in the same horizontal planeand the same sublattice have parallel magneticmoments. We have assumed the following magnetic moment directions: for (9d): z=1/6,z=3/6 , z=5/6 ; for (9e) z=0/6, z=2/6 ,z=4/6 and for (3b) z=1/6 , z=3/6 , z=5/6(where means parallel or antiparallel to agiven direction). The magnetic peaks observedin CaCuxMn7-xO12 lie at 2 angles larger thanthe commensurate (1,0,0),(2,0,0)...etc peakpositions, but they can be indexed as (1,0,),

(2,0, )...etc. Taking into account the similarmagnetic ordering observed in CaMn7O12 [2] itwas assumed that the basic ferrimagneticordering described above is modulated with apropagation vector (0,0, ). The magneticmoments form a helix and they are confined tothe (a,c) plane. The resulting Rietveldrefinement of the neutron powder diffractionpattern observed at 1.5 K with that helicalmodel of the magnetic ordering gave asatisfactory fit. The same model of the magnetic orderingagrees also with the diffraction patternsmeasured at other temperatures up to 40 K.The refined value of the propagation vectorlength =0.145(10) c* corresponds to amodulation period of 43(3) Å and it does notchange with temperature. The values of themagnetic moments of Mn ions in all threecrystallographic sublattices were kept equalduring the refinement.

Another important feature of the magneticdiffraction peaks observed in CaCuxMn7-xO12 isthat they are broader than the neighbouringnuclear peaks. From the broadening one canestimate that the magnetic correlation length in CaCuxMn7-xO12 is about 250(50) Å and itdoes not change with temperature. Such alimited magnetic correlation length was alsoobserved in CaMn7O12 [2] near the magneticphase transition at 49 K.

The full version of the paper has beenpublished in: R. Przenioslo, M. Regulski, I.Sosnowska andR. Schneider J. Phys.: Condens. Matter 14,(2002) 1-5.

References[1] J. Chenavas, J.C. Joubert, M. Marezio and B. Bochu, J. Solid State Chem. 14, 25 (1975).[2] R. Przenioslo, I. Sosnowska, D. Hohlwein, T. Hau,I.O. Troyanchuk, Solid State Comm. 111, 687 (1999).

13

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

cnr

EXPERIMENTAL REPORT

Magnetic structure of the 1-D magnet Na2MnF5

Proposal NPHY-01-1011

Instrument E2

Local Contact

R. Schneider


18. 5. - 21. 5. 2001Principal Proposer: J. Pebler, Philipps Universitat MarburgExperimental Team: J. Pebler, Philipps Universitat Marburg

A. Krimmel, Universitat Augsburg

Date of Report 25. 1. 2002

Introduction

Na2MnF5 belongs to the class of 1-D magnets.Based on neutron powder diffraction experi-ments a purely antiferromagnetic (afm) struc-ture below TN=11.5 K has been proposed in theliterature [1] corresponding to an afm spin ar-rangement with a doubling of the unit cell andthe ordered magnetic moments oriented alongthe the chain direction (crystallographic a-axis).However, recent neutron experiments on singlecrystals revealed an additional magnetic compo-nent along the b-axis, in agreement with singlecrystalline susceptibility measurements. Due todistortions of the MnF6 octahedra in Na2MnF5,such a magnetic component is also plausible froma crystallographic point of view and is also ob-served in other compounds of the fluoromangan-ites.


In order to determine the magnetic structure ofNa2MnF5, single crystal neutron diffraction ex-periments have been performed on the diffac-tometer E2 at the HMI, Berlin. The crystalwas mounted in a cryostat (1.5 ≤ T ≤ 300 K)with the reciprocal lattice vectors a∗ and b∗ inthe horizontal scattering plane. This geometryallowed to monitor all reflections (h, k, 0) for−4 ≤ h/k ≤ +4. Due to the flat cone geome-try of the instrument, the additional plane forl = 1/2 have been investigated. First, the hightemperature diffraction pattern confirmed thehomogeneity and excellent quality of the crys-tal. At T = 25 K, well above the Neel tem-perature, diffuse scattering contributions aris-ing from the 1-D magnetic behavior can be de-tected. At low temperatures, the diffuse scatter-ing is strongly suppressed and additional super-

lattice reflections appear which can be indexedas (h, k±q, 0) with q=(0, 1/2, 0). This implies adoubling along the b-axis, whereas the crystallo-graphic a and c-axis coincide with the magneticcell. Strong and weak reflections are observed forh = even and odd respectively, corresponding toan antiferromagnetic spin arrangement along a.No doubling along the c-axis (h = 1/2) could beobserved.

&RXQWV

77+6

>&$5(66'$7$@('$7 >&$5(66'$7$@('$7

Figure 1: Diffraction pattern of the a∗ − b∗-planeof Na2MnF5 in the magnetically ordered state atT=1.6 K.

[1] P. Nunez, T. Roisnel and A.Tressaud, Sol.State Comm. 92, 601 (1994)

14

EXPERIMENTAL REPORT

B-T phase diagram of the 1-D magnet Na2MnF5


Instrument E2

Local Contact

D. Hohlwein


13. 8. - 19. 8. 2001Principal Proposer: J. Pebler, Philipps Universitat MarburgExperimental Team: J. Pebler, Philipps Universitat Marburg

A. Krimmel, Universitat Augsburg


Introduction

Na2MnF5 belongs to the class of 1-D magnets.Single crystal susceptibility and magnetizationmeasurements revealed a complex B-T phase di-agram (for the external field parallel to the b-axis) which can be described by a field inducedtransition from a purely antiferromagnetic (afm)to a weak ferromagnetic state at low temper-atures. First neutron diffraction experimentson single crystals confirmed an afm structure ofNa2MnF5 with a doubling of the unit cell alongthe b-axis and an afm spin arrangement alongthe magnetic chains with the magnetic momentspredominantly oriented along the a-axis (com-pare with experimental report PHY-01-1011).


In order to relate the magnetic structure ofNa2MnF5 with its complex phase diagram,field dependent single crystal neutron diffrac-tion experiments have been performed on thediffactometer E2 at the HMI, Berlin. Thecrystal was mounted in a vertical cryomagnet(1.5 ≤ T ≤ 300 K and 0 ≤ B ≤ 5 T) with the b-axis along the field corresponding to a∗ and c∗ inthe horizontal scattering plane. First, the mag-netic structure was investigated in zero field. Nosuperlattice reflections could be observed. Sys-tematic reflection conditions are evidenced bystrong (weak) reflections for h or l being even(odd). From the intensity ratios of the differentreflections we infer an afm structure with mag-netic moments of 3.4 µB predominantly alignedalong the chain direction (crystallographic a-axis), however with an inclination of approx 20o

towards b and c. These additional magnetic com-ponents are at the origin of the complex B-Tphase diagram of Na2MnF5. Further field de-

pendent measurements have been performed atT = 6 K and T = 10.9 K. At T = 6 K a spinflop transition occurs around B = 3 T givingrise to a significant ferromagnetic componentalong b (weak ferromagnetism). By contrast,at T = 10.9 K no sharp transition could be ob-served but a smooth continuous increase of theferromagnetic component upon increasing mag-netic field. For B ≤ 4 T significant diffuse scat-tering contributions arise from spin fluctuationsalong the chains which become strongly sup-pressed for B ≥ 4 T.

&RXQWV

77+6

>&$5(66'$7$@('$7 >&$5(66'$7$@('$7

Figure 1: Diffraction pattern of Na2MnF5 in the1-D magnetic state as evidenced by the charac-teristic strong diffuse scattering contributions.

15

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Y*5 E H2 \!H 3 2 1 E c P f P c e e c

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0 0.5 1 1.5 2 2.5 3 3.5T (K)

-92.7

-92.6

-92.5

-92.4

-92.3

-92.2

ϕ (o )

0 0.5 1 1.5 2 2.5 3 3.5T (K)

0

0.2

0.4

0.6

0.8

1

Int.

Inte

nsity

I/I 0

(000)+

(110)+

CeCu2(Si1-xGex)2

x = 0.5

3

Ã=W v%n V f É=*V $9V n q k v%n Vyz%V 9V X%z%V X%l VyR x*k S!VW X k V X!bu W k R x*k S%Vq X%V k W l$ e e e Êq Xz f f e! Ê¶9V q m%uW Xw?V wv' j!W ¿ À Á V ¿ À Á ' PS%VT R UV n9q X%V T=u S%R Uyuyk S!V9R!u W k W R!X"R xk S!V e e e! Ê9V q m9Pl q k W X% q9R!u u W T VT R%l m!b W X$k n q X%u W k W R X k R ql R $V X%bu v%n q k Vu k n v%l k v!n V u V VÃ=W %Pf PÃ%R n=k S%VT V u uS!V q %W T z%R 9V z|q T T R %u" ¨Ëe!« ´ X!Rk n q Xu W k W R!X%uy9V T R U°*ºq n VR 9u V n V z*Pj%W X%l Vq !X!V k W l"?n q |9V q m%u$q n VV V X|R 9u V n V zx R n ¨³e%« e ÚyS%W l SW u l R Xu W z!V n V zk R¶V r%SW W kv%Xl R X V X k W R!X%q Tyb 9S%q u V|q !X!V k W u oqq Ì R n$u k V |k R Uq n z%u k S!V"vX%z%V n u k q X%zW X!W Xk S!Vb 9S%q u V W X"9v!n V$w?V wv%' j!W 'yW uq z!V P f ¡$P·X%V 9V TV kq T P os?S %u P~V 9PÍ£Î%Ï*o f f ´ ` ¬ f Ð Ð ¬! µ h P *n R q n V T T W!V kq T P o s?S %u P!~V 9P ÍÎ%Ñ*o¬!a ` f Ð Ð a P

c ¡$ P·yn W $V TV kq T P os?S %u P~V 9PÎÎ9o¬ %f ¬ f Ð Ð a µ% P ·yn W $V T o P Ò*R W zT o s?S %u W l qy K ÏÓÔ K ÏÑ*o` a a f Ð Ð a P

16

cim

EXPERIMENTAL REPORT

Magnetic structure of CePt5Ge3 and CePd5Ge3


Instrument E2

Local Contact

D. Hohlwein


5.-8.11.2001

26.-29.11.2001

Principal Proposer: O. Stockert, Max-Planck-Institute CPfS Dresden

Experimental Team: Z. Hossain, M. Deppe, Max-Planck-Institute CPfS

Dresden

D. Hohlwein, P. Smeibidl, HMI Berlin


The ternary rare-earth compounds CePt5Ge3and CePd5Ge3 order antiferromagnetically at

TN = 1:1K and 1:9K as evidenced by maxima

in the specic heat and susceptibility. Whereas

CePt5Ge3 shows pronounced features of short-

range AF correlations above TN indicated by a

shoulder of the specic heat, the isostructural

CePd5Ge3 only exhibits 3D AF order. In order

to determine the magnetic order in both com-

pounds and to shed light on to the short-range

correlations in CePt5Ge3 we performed powder

neutron diraction on E2 at temperatures be-

tween T = 50mK and 5K using a wavelength of

the neutrons of = 2:39 A.

Diraction pattern were taken at T = 5K

or 10K in the paramagnetic phase and in the

magnetically ordered phase at dierent temper-

atures down to T = 50mK. The crystal struc-

ture of both compounds was conrmed to be or-

thorhombic (space group Pnma) with the fol-

lowing lattice parameters: a = 20:204(2) A,

b = 4:1171(6) A, c = 7:240(1) A for CePt5Ge3(10K) and a = 20:186(7) A, b = 4:109(2) A,

c = 7:227(3) A for CePd5Ge3 (5K). The non-

magnetic contribution (5 or 10K data) was sub-

tracted from the low T data to get just the

magnetic part of the scattering. Fig. 1a shows

the resulting diraction pattern of CePd5Ge3 at

T = 50mK which should mainly contain the

magnetic scattering. Unfortunately most of the

peaks visible in Fig. 1a are at positions of nu-

clear peaks and could probably be due to im-

proper subtraction. Only the peak at 2 14:5Æ

is unambigiously of magnetic nature and can

be indexed as (000) + with a wave vector

(0 0:44 0) assuming that the modulation of

the magnetic moments is along the b-axis along

which the Ce atoms form chains. The temper-

ature dependence of this fundamental magnetic

sattelite is displayed in Fig. 1b. The magnetic in-

tensity vanishes at 2K in good agreement with

the thermodynamic results. In CePt5Ge3 we

found at the same 2 position as in CePd5Ge3a magnetic peak but with much lower inten-

sity suggesting that both compounds exhibit the

same type of incommensurate antiferromagnetic

order. Despite long measuring times at temper-

atures above TN no traces of additional magnetic

intensity were observed in CePt5Ge3 as an indi-

cation of short-range AF correlations.

0 10 20 30 40 50 60

0

200

400

600CePd Ge

3

2θ (degree )

5

I(0.

05 K

- 5

K)

(a.u

.)

0.0 0.5 1.0 1.5 2.0

0

100

200

300

400

500

CePd5Ge

3

Inte

nsity

T (K)

(000)+

(a.u

.)

(000)+

(a)

(b)

Figure 1: (a) Dierence diraction pattern

(50mK - 5K) of CePd5Ge3 powder recorded on

E2 ( = 2:39 A). (b) Temperature dependence

of the magnetic (000)+ peak.

17



Instrument E2Magnetic phases of TmCu2 single crystal in horizontal magnetic field

Local Contact R. Schneider

Principal Proposer: Svoboda Pavel Charles Univ., Prague Date(s) of ExperimentExperimental Team: Vejpravová Jana Charles Univ., Prague

5.8. – 13.8. 2001


TmCu2 belongs to the series of orthorhombic inter-metallic compounds RCu2 (R = rare earth metal) whichhas attracted new attention within last years due to theso-called conversion of the Ising axis in high magneticfields [1]. We have succeeded to grow new high-qualitysingle crystal of TmCu2 by Czochralski pullingtechnique. On this crystal we performed the detailedmicroscopic study of the magnetic phase diagram in fieldparallel to the b-axis, which is the easy axis ofmagnetization. Already from the first neutron diffractionexperiment on E6 diffractometer in September 2000 wefound that the magnetic phase diagram is extremelycomplex [2] and we were able to describe just several ofthe observed phases. To clarify the situation we haveperformed a detailed diffraction experiment on E2diffractometer using VM3 vertical cryomagnet [3]. Theonly remaining uncertainty was the propagation alongthe b-axis, which we were not able to study in thevertical geometry. To clarify that we performed theexperiment using the horizontal cryomagnet HM2 withthe sample mounted in the a-b scattering plane and b-axis parallel to the magnetic field. From the detailed experiment in both vertical andhorizontal magnetic fields we were able to determine thefinal magnetic phase diagram presented on Fig. 1.

Fig. 1: Magnetic phase diagram of TmCu2 in B||b axis.The gray areas correspond to the co-existence of phasesand demonstrate the first-order phase transitions.

The ground-state phase AF1 corresponds to the squared-up magnetic structure with magnetic moment parallel tothe b-axis, consisting of ferromagnetic b-c planesantiferromagnetically stacked along the a-axis withmagnetic unit cell 8a x b x c and characterized by apropagation vector 01 = (5/8 0 0) (see Fig. 2).

Fig. 2: The magnetic unit cell of the ground-state phaseAF1. The magnetic structure consists of theferromagnetic b-c planes antiferromagnetically stackedalong the a-axis with the ++--+--+--++-++-(+) stacking.

The other antiferromagnetic and ferrimagnetic phases arejust ‘spin-slip’ or sinusoidal wave (SW) derivatives ofthis ground-state phase with the propagation vectors asindicated in Fig. 1. Finally, above the FM4 phase, thereis field-induced ferromagnetic (or paramagnetic) phasewith the (0 0 0) propagation. We may conclude, that using the unique possibilities ofthe E2 diffractometer in combination with bothhorizontal HM2 and vertical VM3 cryomagnets we wereable to determine 8 different magnetic phases in thetemperature region 1 – 6 K and in magnetic fields up to0.5 T with high accuracy.

References:[1] P. Svoboda et al., Europhysics Letters 48 (1999) 410[2] P. Svoboda et al., Exp. Report on PHY-01-913, HMI[3] P. Svoboda et al., Exp. Report on PHY-01-947, HMI

18

cnr

EXPERIMENTAL REPORT

Antiferromagnetic order in UCu4Pd


Instrument E2

Local Contact

D. Hohlwein


8. 11. - 9. 11. 2001Principal Proposer: A. Krimmel, Universitat AugsburgExperimental Team: A. Krimmel, Universitat Augsburg


Introduction

During the last decade, a large number of f -electron systems have been found whose anoma-lous low temperature properties cannot be rec-onciled with conventional Fermi-liquid theory,including UCu5− xPdx. Most frequently, suchnon-Fermi-liquid (NFL) behaviour is observedin alloy series around a critical concentrationfor one of its constituents. In general, disorderis always present in such alloy series. There-fore disorder-driven models have been proposedto explain NFL behaviour. UCu4Pd has beenconsidered as an archetypical example exhibit-ing disorder driven NFL. However, almost all ex-periments on UCu4Pd have been performed onas-grown samples. Additionally to the increasingexperimental evidence for crystallographic order,it has been observed that as-grown samples ex-hibit a magnetic transition around T = 170 mKin contrast to annealed samples displaying NFLbehaviour, as evidenced by specific heat and re-sistivity measurements [1]. This is in sharp con-trast to any disorder based NFL model. Thecrucial test is the direct determination of bulklong range magnetic order of UCu4Pd by neu-tron diffraction.


In order to look for long range magnetic or-der in UCu4Pd and to determine its magneticstructure, single crystal neutron diffraction ex-periments have been performed on the diffac-tometer E2 at the HMI, Berlin. NFL behaviouris observed on the verge of a magnetic insta-bility. Therefore, the experimentally observedmagnetic transition in UCu4Pd only involvesvery small magnetic moments and hence singlecrystal measurements are indispensable.

Samples have been grown the Zchrchalskytechnique and were characterized by Laue x-raydiffraction indicating single crystalline material.However, investigating the bulk properties of thesample by neutron diffraction at room tempera-ture showed poor sample quality, at least con-cerning the crystallographic properties. Onlypart of the allocated beam time has been usedsince it became evident that the sample was amultidomain crystal and thus in fact not singlecrystalline material. This prohibited any reason-able low temperature measurements to look forlong range magnetic order in UCu4Pd. Indeed,no well defined Bragg peaks could be observedat all, but rather powder lines exhibiting somesmall modulation in intensity. This exemplifiesagain that neutron diffraction is the only methodto investigate the bulk properties of a sample.

[1] A. Weber, S. Korner, E.-W. Scheidt, S.Kehrein and G. R. Stewart, Phys. Rev. B 63,205116 (2001)

19

ef_06 // J.-U. Hoffmann // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EFInstrument E2Magnetic correlations in La0.9Sr0.1MnO3Local Contact D. Hohlwein

Principal Proposer: J.-U. Hoffmann, BENSC, Univ. Tübingen Date(s) of ExperimentExperimental Team: J.-U. Hoffmann, BENSC, Univ. Tübingen 12.-21.2.2001

D. Hohlwein, BENSC, Univ. Tübingen 1.-6.5.2001R. Schneider, BENSC, Univ. Tübingen 15.-17.5.2001

Date of Report: 21.1.2002For lightly hole doped La1-xSrxMnO3 only asmall colossal magneto-resistance (CMR)effect can be observed. We investigated aLa0.9Sr0.1MnO3 single crystal to compare themagnetic properties with the compounds ofx=0.15 [1] and x=0.2. The single crystal waskindly provided by Martine Hennion (LLBSaclay). First results were presented in the lastBENSC Exp. Report. [2].We used the E2-Flat-Cone diffractometer witha wavelength of 2.39 Å and studied atemperature range between 1.5 K and 300 K.The lattice structure is orthorhombic (Pbnm).We determined the domain distributionanalogous to the case of pure LaMnO3 [2]. The magnetic structure is a cantedantiferromagnet. We found the ferromagneticphase transition temperature at TC = 145 K(fig. 1) and the antiferromagnetic one atTAF = 120 K. We observed a charge orderbelow TCO = 97 K.

The diffuse scattering distribution in thecomplete horizontal layer of reciprocal spacewas fited with the program TVtueb (R.Schneider and J.-U. Hoffmann) by using anextended mean field theory (fig. 2). Theexchange parameters Jab (in the ab plane) andJc (along the c-axis) vary linearly (fig. 3). Thisbehavior was observed in the La0.8Sr0.2MnO3compound, too.

[1] J.-U. Hoffmann, D. Hohlwein, R. Schneiderand A.H. Moudden; Physica B 276-278 (2000)608-609

[2] J.-U. Hoffmann et al; BENSC ExperimentalReport 2000, Diffuse scattering and domaindistribution in La1-xSrxMnO3 with x=0 andx=0.1.

0

5000

10000

15000

20000

25000

30000

0 50 100 150 200 250 300Temperature in K

Am

plitu

de

Cou

nts/

45s

(1 0 0) 10x (2 1 0) (2 0 0) (0 0 1)(1 -1 0) 1/3x (001) H = 4.5T (1 -1 0) 1/3x H = 4.5T

Fig. 1: Intensity of the (100), (210), (200), (001) andthe (001) orthorhombic peak. Open symbols aremeasurement with a magnet field of H=4.5 T.

5.0 10.0 15.0 20.0 25.0 30.0 35.0

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

h

k

Experiment

Theory

countsFig 2. Diffuse scattering of La0.9Sr0.1MnO3 with thetwin pattern in the zero layer (reciprocal Angstrom).Fit of an extended mean field theory with Jab = 10.8 Kand Jc = 1.1 K at T = 175 K.

8

10

12

14

16

18

20

150 170 190 210 230 250 270 2900

2

4

6

8

10

12

Exch

ange

par

amet

er J

in K

ab

Exch

ange

par

amet

er J

in K

c

Temperature in K

Fig. 3: The exchange parameter Jab and Jc as a functionof temperature.

20

EXPERIMENTAL REPORT Proposal N° EFInstrument E2Magnetic diffuse scattering in

La0.8Sr0.2MnO3 Local Contact Dietmar Hohlwein

Principal Proposer: J.-U. Hoffmann, BENSC, Univ. Tübingen Date(s) of ExperimentExperimental Team: J.-U. Hoffmann, BENSC, Univ. Tübingen 25.- 26.6.2001

D. Hohlwein, BENSC, Univ. Tübingen 2.- 8.7.2001R. Schneider, BENSC, Uni. Tübingen 30.7. – 5.8.2001

30.8. – 2.9.2001Date of Report: 21.1.2002

The colossal magneto-resistance (CMR) effectin the hole doped La1-xSrXMnO3 compounds isconnected with the magnetic double-exchangeinteraction between the manganese ions. We have analyzed already the diffusemagnetic neutron scattering in theparamagnetic phase of the compound (x=0.15)with the maximal CMR effect [1]. Here, weinvestigated a single crystal with x=0.2, whichhas a smaller CMR effect. The single crystalwas kindly provided by A.H. Moudden (LLBSaclay).

Measurements were done at the E2-Flat-Conediffractometer with a wavelength of 1.21 Å andin a temperature range between 190 K and330 K. The phase transition temperature wasdetermined as TC = 299.1 K (Fig.1).

-6.0 -4.0 -2.0 0.0 2.0 4.0 6.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0 Experiment

Theory

h

k

Fig.2: Reciprocal space with the diffuse scatteringfrom the experiment and calculated by mean-fieldtheory in reciprocal Angstrom.

Inve

rsrs

e su

scpt

ibilit

y 1/

chi(0

00)

Temperature T in K

Fig. 3: Inverse susceptibility. The red line (steeperone) is the trend of the mean field theory with aconstant exchange parameter.

0

200

400

600

800

1000

190 210 230 250 270 290 310 330Temperatur in K

(020) (110) (200) (220) Hohe Temperaturen Tiefe Temperaturen

Nor

mal

ized

inte

nsiti

es o

f the

mag

netic

pea

ks

Fig. 1: The peak intensities of (200), (020), (110)and (220) in the orthorhombic structure (Pbmn). Anormalization of the magnetic contribution wasdone.

ef_05 // J.-U. Hoffmann // 21.03.02 Seite 1 von 1

With the banana-type multi detector completelayers of the reciprocal space were recorded.The diffuse scattering was fited with thesoftware TVtueb (R. Schneider and J.-U.Hoffmann) by a mean field theory. We usedthe pseudo cubic approximation and only oneexchange parameter. The exchangeparameter J changes linearly with temperatureand the derivative of the susceptibility is not inagreement with the mean field theory. The

inverse susceptibility (fig. 3) changes stronglyat T ≈ 335 K. In the conventional mean fieldtheory a J of 14.8 K would give a phasetransition at TMF= 331 K, but the observedtransition temperature is 32 K lower.

[1] J.-U. Hoffmann, D. Hohlwein, R. Schneiderand A.H. Moudden; Physica B 276-278 (2000)608-609

21

cnr


EXPERIMENTAL REPORT Proposal N° EFInstrument E2Magnetic Structures in Iron doped

Y0.1Ca0.9MnO3 Local Contact D. Hohlwein

Principal Proposer: W. Prandl, Univ. Tübingen Date(s) of ExperimentExperimental Team: D. Hohlwein, BENSC, Univ. Tübingen 27-29.8.2001

9-12.11. 200130.11.-5.12.2001


The magnetic structure of Y0.1Ca0.9MnO3consists of three components as in theanalogous compound with Ho instead of Y [1]:an antiferromagnetic A structure with spindirection along the z-axis, Az, a secondantiferro component Cx and a ferromagneticcomponent Fy. The ferromagnetic componentgives rise to an increase of the electricalconductivity due to the double exchangeinteraction.We studied the change of magnetic structureas a function of Fe3+ doping concentration onthe manganese place.Powder spectra were collected at the E2instrument with wavelengths 1.21 and 2.39 Aas a function of temperature. We investigatedthe compounds Y0.1Ca0.9Mn1-xFexO3 with x =0.005, 0.01 and 0.04.The different components of the magneticstructure can be seen in the intensities ofspecific reflections. These are shown in Fig.1and Fig.2 for the antiferro components Az andCx and in Fig.3 for the ferro component Fy.We can see that at higher doping levels allcomponents are reduced and for two of it alsothe phase transition temperature is shifted tolower temperature. The largest effect can beseen for Fy which is connected to the doubleexchange interaction and the electricalconductivity. Az with spin components along zhas the smallest change. So the magneticmoments with components in the doping planeare mostly affected. The magnetic momentsdetermined by Rietveld analysis will becompared with the electrical conductivity of thecompounds.

[1] K. Hagdorn, D. Hohlwein et al. Eur. Phys. J. B 11, 243-254 (1999)

0 20 40 60 80 100 1200

2000

4000

6000

8000

10000

12000

2=32.25°, Az(110)

Fe0.04

Fe0.01

Nor

mal

ized

inte

nsity

T [K]

Y0.1Ca0.9Mn1-xFexO3

Fig.1 : Intensity change connected with the Az

Antiferro component

0 20 40 60 80 100 1200

50

100

150

200

250

300

350

400

450

500

550

600

Y0.1Ca0.9Mn1-xFexO3

2=18.5°, Cx

Fe0.04

Fe0.01

Nor

mal

ized

Inte

nsity

T [K]

Fig.2 : Intensity change due to the C x component

0 20 40 60 80 100 1200

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

2= 37.45°, Fy(101)

Fe0.04

Fe0.01

Nor

mal

ized

Inte

nsity

T [K]

Y0.1Ca0.9Mn1-xFexO3

Fig.3 : Intensity change due to the Fy ferro component

22


EXPERIMENTAL REPORT Proposal N° EFInstrument E2Spin correlations and interactions in the

paramagnetic phase of MnO Local Contact D. Hohlwein

Principal Proposer: D. Hohlwein, BENSC, Univ. Tübingen Date(s) of ExperimentExperimental Team: D. Hohlwein, BENSC, Univ. Tübingen 9.10. – 21.10. 01

6.12. – 10.12. 01


Spin correlations and magnetic interactionparameters can be determined from themagnetic diffuse scattering in the para-magnetic phase. The existing theories are onlyapproximate and can be compared withexperiments. In the past, we have shown thatin the tetragonal antiferromagnet MnF2, themean-field theory has to be extended by anOnsager parameter [1].MnO is a cubic (fcc) antiferromagnet with afirst order transition at TN = 120 K due to asimultaneous rhombohedral lattice distortioncaused by magnetostriction. The magneticstructure consists of ferromagnetic sheetsparallel to the (111) plane with the momentdirections within the plane and directionsantiparallel in adjacent sheets.A single crystal of about 0.5 cm3 has beenmounted with a <110> axis vertical on the E2instrument. The diffuse scattering distributionhas been recorded in complete (hhl) layerswith omega steps of 0.25° and the bananadetector in the 2theta range from 5 – 85°. Thewavelength was 1.21 A and the temperaturerange from 120 to 260 K. The diffuse scattering distribution at 200 K isshown in Fig. 1. In the upper part of the figurewe see the experimental data together withBragg reflections and in the lower part thediffuse scattering refined by a mean-fieldtheory. The refinement was done with theprogram TVtueb (J.-U. Hoffmann and R.Schneider) using two interaction parameters J1(12 nearest neighbours) and J2 (6 next-nearestneighbours). The anisotropy of the diffusescattering is due to the fact that bothparameters are of comparable size. At 200 Kwe got J1 = -2.82 K and J2 = -3.77 K and at130 K we found –2.41 and –3.40 K. Thesevalues can be compared to the results frommagnon measurements at 4 K [2] in thedistorted phase J1 = -4.2 K und J2 = -4.8 K.The discrepancy can be due to the change ofthe lattice constant or to the limited accuracy ofthe mean-field theory. The temperaturedependence of the inverse susceptibility at

(0.5,0.5,0.5) is shown in Fig.2 . The behaviournear the phase transition has to be studiedfurther in more detail.

-6.0 -4.0 -2.0 0.0 2.0 4.0 6.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

Fig.1: Diffuse scattering in the (hhl) plane ofMnO at 200K. Upper half experimental dataand lower half fit to a mean-field theory.

120 140 160 180 200 220 240 2600.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

MnO, 1/ with = Idiff(0.5,0.5,0.5)/T

1/(0

.5,0

.5,0

.5)

T [K]

Fig.2: Inverse susceptibility at the reciprocallattice point (0.5,0.5,0.5).

[1] D. Hohlwein, Applied Physics A, in print(2002)[2] G. Pepy, J. Phys. Chem. Solids 35, 433(1974)

23


EXPERIMENTAL REPORT Proposal N° EFInstrument E2Diffuse magnetic scattering above Tc in

quasi-2D La1.2Sr1.8Mn2O7 Local Contact Rainer Schneider

Principal Proposer: Tapan Chatterji, ILL Grenoble Date(s) of ExperimentExperimental Team: Rainer Schneider, Universität Tübingen

Tapan Chatterji, ILL Grenoble 22.02.01- 25.02.01


The exchange interaction introduced independently byHeisenberg and Dirac in 1926 is key to understandingmagnetic properties of materials, includingtechnologically relevant colossal magnetoresistive(CMR) manganites. Here we show that the diffusemagnetic scattering above the magnetic transitiontemperature can yield exchange parameters. We havemeasured the magnetic diffuse scattering from the quasi-2D bilayer manganite La1.2Sr1.8Mn2O7 which showsCMR behavior close to the ordering temperature TC. Byfitting the experimentally measured intensity distributionof the diffuse scattering in the (h0l) plane to modelmean-field calculations, we have been able to determinethe nearest neighbor exchange interaction between theMn ions in the a-b plane and also that between the twoplanes of the bilayer.

a a

cc

aJc

Figure 1: structure of La1.2Sr1.8Mn2O7 andtemperature/magnetic field dependence of its resistivity.

10.0

20.0

30.0

40.0

50.0

60.0

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

h

-10.0

-5.0

0.0

5.0

10.0

Figure 2: diffraction pattern of the h0l plane at roomtemperature (left upper) compared to mean-field calculation(right lower part). The diffuse intensity distribution arisingfrom the short-range magnetic order can be well described bythe extended mean-field model of the magnetic interactions.

[1] T. Chatterji, R. Schneider, J.-U. Hoffmann, D. Hohlwein, R. Suryanarayanan, G. Dhalenne and

A. Revcolevschi, Physical Review B, accepted (to be published in April 1 issue, 2002)

24


EXPERIMENTAL REPORT Proposal N° EFInstrument E2Paramagnetic short-range order in TbLocal Contact Rainer Schneider

Principal Proposer: Rainer Schneider, Universität Tübingen Date(s) of ExperimentExperimental Team: Rainer Schneider, Universität Tübingen

Tapan Chatterji, ILL Grenoble 20.03.01- 25.03.0102.10.01- 08.10.01


The rare-earth metal terbium exhibits anincommensurate helical magnetic structure within anarrow temperature regime below the Néel-point ofT=228 K. In this experiment we used a terbium singlecrystal and studied complete planes of the reciprocalspace to get more information about the magneticinteractions in the paramagnetic phase. Effectiveexchange parameters up to a distance of 14A could bedetermined using an extended mean-field theory. Abovethe paramagnetic phase-transition a complicated diffusescattering pattern is found within [h0l] plane. Thisintensity distribution could be well described by anextended mean-field theory using only six interactionparameters and one crystal field parameter. Figure 1shows the measured and calculated intensitydistributions for T=235 K in reciprocal space. Thedetermined effective coupling constants describinginteractions parallel c-axis are plotted in figure 2 versusthe atomic distance. These parameters could beexcellently fitted by a Friedel-oscillation.The exchange interactions in terbium are of very longrange. Even at atomic distances of more than twice thelength of the hexagonal c-axis the resulting couplingparameters are not negligible. This fact corresponds tothe results of earlier calculations for holmium. Theoscillating behaviour of J(d) by varying the atomicdistance is expected for a system with a magneticexchange interaction of localised magnetic momentscaused by polarisation of conduction electrons.

2 4 6 8 10 12 14 16 18-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

exch

ange

inte

ract

ions

Jij

atomic distance [A]

Fermi-surface of Terbium

Friedel-oscillation

0

100

200

300

400

500

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

h

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

235 K

0

100

200

300

400

500

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

h

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

Figure 1: The upper diagram shows the intensity distributionwithin the (h0l) plane at T= 235K. The lower one displays thefitted diffuse scattering contribution and is in good agreementwith the experimental data.

Figure 2 (left): magnetic exchange interaction parameters alongthe hexagonal axis could well described by a Friedel-oscillation.

[1] Jensen J and Mackintosh A R : “Rare Earth Magnetism”, OxfordScience Publications 1991

25

EXPERIMENTAL REPORT

A Structure Factor study, looking for a Magnetic

Moment on the Nickel site in TmNi2B2C.


Instrument E4

Local Contact

K. Prokes


14. 2. - 23. 2. 2001

Principal Proposer: Katrine Nrgaard Toft, Ris National Laboratory

Experimental Team: N. H. Andersen, Ris National Laboratory

P. Smeibidl, Hahn-Meitner Institut

S. Kausche, Hahn-Meitner Institut


In TmNi2B2C superconductivity (Tc = 11 K)

coexists with magnetic order (TN = 1.6 K).

Applying a magnetic eld perpendicular to the

magnetic moments suppresses superconductivity

and induces a magnetic order which is a Fermi

surface nesting structure.Two properties of this

magnetic phase ( ~Q = (0.48,0,0)) cannot be un-

derstood within any known theories. First of

all, the intensity is saturated at low tempera-

tures, decreases linearly until approx. TN = 3-4

K, but instead of disappearing it has a low in-

tensity tail, which sustains as high as to TT =

10 K. Second of all, the transition temperatures

TN and TT increases in increasing eld.

Both of these phenomena might be explained

by the appearance of a magnetic moment on the

nickel site, assuming rst of all, that it orders in

the magnetic structure with a low intensity sig-

nal at ~Q = (0.48,0,0) and a transition tempera-

ture of TT , and second of all, that TT increases

in increasing magnetic eld.


This experiment examined the structure factors

of the magnetic peaks at (h; k; l) (0:48; 0; 0).

If a magnetic moment is present on the nickel

site all magnetic peaks at k; l = 0 increases,

whereas the magnetic peaks at k; l = 1 stays the

same. We have done transverse and longitudinal

scans through the following peaks: (0:48; 0; 0),

(1:52; 0; 0), (0:52; 0; 1), (0:52; 0; 1), (1:48; 0; 1),

and (1:48; 0;1) at a magnetic eld of 24 kOe.

The scans were done at 0.1 K, where the inten-

sity arising from the nickel moment constitutes

only a small fraction of the total intensity, and

at 4 K where all the intensity should come from

the nickel moments.

The structure factor of four of the peaks does

not depend on a nickel moment, whereas the two

remaining peaks has a larger structure factor in

the case of a nickel moment. Setting the relative

change to zero in average for the four peaks, the

result gives an average increase of 7 % for the two

peaks. The standard deviation of each intensity

is as large as 5-7 %, however using averages the

standard deviation of the mean is down to 2.5

%. So we conclude that it is possible that there

is a magnetic moment on the nickel site, but for

a more conclusive answer, more peaks should be

scanned.

Figure 1: Overview of the resolutions in re-

ciprocal space with grid scans of several mag-

netic peaks in an applied magnetic eld of 40

kOe, and T = 500 mK. The (0:52; 1; 0) and

(0:52; 1; 0) scans are done in the (a; c) plane,

whereas the (0:48; 0; 0), (1:52; 0; 0) and (2; 0; 0)

scans are from the (a; b)-plane.

Figure 1 shows a visualisation of the peaks in

reciprocal space. Notice that there are two peaks

in the two upper scans, the already known one at

(0:52; 0; 1) and one at (0:505; 0; 1) which appears

above 36 kOe. It is believed that the second peak

emerges from small changes of the Fermi surface,

thus introducing a second magnetic structure.

26

EXPERIMENTAL REPORT

Single crystal study of the magnetically frustrated

gadolinium gallium garnet


Instrument E4

Local Contact

K. Prokes and E. Garcia Matres


October 11-21 2001

Principal Proposer: Henrik M. Rnnow, CEA Grenoble

Experimental Team: Oleg A. Petrenko, University of Warwick

Date of ReportFebruary 27, 2002

Introduction

Geometric frustration makes Gd3Ga5O12 a very

interesting system with a rich behaviour in-

cluding spin-glass-like behaviour in low mag-

netic elds and a eld induced antiferromag-

netic phase. Neutron powder diraction has pro-

vided some insight into these phenomena, but

a more detailed understanding requires single

crystal measurements.


The horrendous absorption cross-section of nat-

ural Gadolinium was compensated for by using a

high quality single crystal wafer with a large sur-

face area. The sample had (100) as plane normal

and was mounted with (0; 1; 1) vertical in the

horizontal eld cryomagnet HM-2. This geome-

try enabled us to apply the eld along all three

major symmetry directions: (1,0,0), (0,1,1) and

(1,1,1). To identify Bragg re ections with mag-

netic contributions, the integrated intensity was

recorded from rocking curves of 10-16 inequiva-

lent re ections for each direction of the applied

magnetic eld.

For Bjj(011), the results were generally consis-tent with earlier data from HMI, ILL and Ris.

The eld dependency of e.g. (6,0,0) displays a

double peak structure suggesting that there are

in fact two AFM phases.

With Bjj(100), re ections (hkk) with h odd,

all showed similar behaviour with the eld, as

seen for (500) in gure 1. The left hand in-

sert demonstrates that the ordered phase dis-

appears between 350 mK and 400 mK. Deter-

mination of the full phase diagram was prohib-

ited by equilibration times up to 16 hours after

changing the temperature. This could either be

due to thermalisation problems between sample

and the thermometer at the mixing chamber, or

due to intrinsic slow equilibration processes in

GGG, which in zero eld has been proposed to

exhibit glassy behaviour at the lowest temper-

atures. No intensity was observed at the (200)

re ection, which in a previous experiment with

Bjj(001) was seen to peak around 0.5 T. This

could suggest that the low-eld AFM phase has

its moments aligned anti-paralell to the eld.

The present experiment was the rst time

that measurements have been performed with

the eld along (111). The eld dependence of

the magnetic peaks seemed to be a combination

of what is observed more sharply for Bjj(100)and Bjj(011) respectively. This implies the im-

portant information that (111) is not a high sym-

metry direction for the magnetic anisotropies in

the system.

0 0.5 1 1.5 2 2.5 30

20

40

60

80

100

B||(100) [T]

Peak

Int

ensi

ty /

sec

Field profiles converged for each temperature

50 mK 50 mK*200 mK300 mK350 mK

0 10 200

20

40

60

# ramps of 80 min

Inte

grat

ed in

t

0 200 400Temperature [mk]

Figure 1: Peak intensity of the (500) re ection as

a function of applied magnetic eld along the (100)

direction. The blue circles correspond to the virgin

curve after several days at base temperature. The

remaining 4 curves were taken once the integrated

intensity had converged reasonably (right hand in-

sert).

27

MAT-01-0963 // brandt // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° MAT-01-963

Instrument E4Magnetic structure above the metamagnetic transitionfield in heavy fermion superconductor UPd2Al3

Local Contact Karel Prokeš

Principal Proposer: Naofumi Aso, NSL-ISSP, Univ. of Tokyo Date(s) of ExperimentExperimental Team: Naofumi Aso, NSL-ISSP, Univ. of Tokyo

Karel Prokeš, BENSC HMIElvira Garcià-Matres, Univ. Augsburg

14-26. 5. 2001


UPd2Al3 is a well-known heavy fermionsuperconductor with a crystal structure ofP6/mmm. It orders antiferromagnetically at TN= 14.3 K, in which the magnetic moments of0.85 B/U are aligned ferromagnetically in thea-b plane and coupled antiferromagneticallywith a wave vector k = [0,0,1/2]. Below Tc ~ 2.0K, it becomes superconducting coexistent withthe antiferromagnetic ordered phase. A lot ofstudies so far revealed that uranium 5felectrons are responsible for the above twolong-range ordered states. Another interestingaspect is that UPd2Al3 shows themetamagnetic (MM) transition at Hm = 18 Tapplied in the basal a-b plane with an inducedmoment of 1.4 B/U. To investigate the natureof the MM transition in UPd2Al3, we believethat we need to determine the magneticstructure in the high field phase (HFP) aboveHm. Neutron scattering measurement undersuch a steady high magnetic field of 18 T,however, could not have been performed. Veryrecently we have succeeded in growing singlecrystals of Ga-doped UPd2Al3 [1]. As thealuminum atoms are substituted by the galliumones, the MM transition field gradually reducesdown to 13 T for UPd2(Al0.7Ga0.3)3. Thereforeelastic neutron scattering experiments onUPd2(Al0.7Ga0.3)3 were performed on the E4spectrometer under magnetic field of up to14.5 T. Details of the experimental conditionare show in the Fig. 1.

At the neutron scattering facility of JRR-3Mreactor in Japan, we have already performedelastic neutron scattering measurement onUPd2(Al0.7Ga0.3)3 under zero field to investigateits magnetic structure and confirmed that it hasthe same antiferromagnetic structure as that ofUPd2Al3 with the wave vector of k = [0,0,1/2].

Figure 1 illustrates the magnetic fielddependence of the antiferromagnetic Braggpeak at Q = (0,0,0.5) obtained at T = 1.8 K. Ascan be seen clearly, intensity starts decreasingaround 12 T, drops sharply around 13 T, and itdisappears at H = 14 T. Futhermore themagnetic field dependence of the intensity of

the nuclear Bragg peak at Q = (0,0,1) (notshown here) indicates that the intensityincrease abruptly around 13 T. These findingsprove that the magnetic structure in the HFP isa not-canted, simple ferromagnetic one.

In both antiferromagnetic low-field phase(AFLFP) below Hm and the HFP above Hm, thede-Haas van Alphen (dHvA) signals areobserved in this system. On the basis of theband calculation regarding uranium 5felectrons as itinerant, in good agreement withthe dHvA signals, 5f electrons in AFLFP areitinerant. Since branches with heavy cyclotronmass are found also in HFP, the MM transitionin UPd2Al3 is a transition from the itinerantantiferromagnet to the itinerant ferromagnet.Although pioneering measurements of themagnetization have been claiming that the MMtransition breaks the heavy fermion state intothe localized 5f electrons state [2], these ideasare denied from this work.

3,000

2,500

2,000

1,500

1,000

500

0

Inte

nsity

/M50

000

-8x10-3

-4 -2 0 2 4 6 8

[H,H,0.5] (r.l.u.)

HMI-E4(2-axis)λ=2.44A, 40'-40'-40', T=1.8K, Q=(0,0,0.5)

0T 2T 4T 6T 8T 10T 11T 12T 12.5T 13T 13.5T 14T 14.5T

Figure 1. Magnetic field dependence of theantiferromagnetic Bragg peak at Q=(0,0,0.5) inUPd2(Al0.7Ga0.3)3

[1] N. Aso et al., Physica 259-261 (1999) 636.[2] K. Sugiyama et al., Physica B186-188(1993) 723.

28


EXPERIMENTAL REPORT Proposal N°PHY-01-964

Instrument E4 Spin structure determination of the metamagnetFeI2 in applied magnetic field Local Contact

Karel Prokes

Principal Proposer: K. Katsumata, RIKEN, Japan Date(s) of ExperimentExperimental Team: H. Aruga Katori, RIKEN, Japan

K. Prokes, HMI, Germany May 2001

Date of Report: January 22, 2002

The compound FeI2 has a hexagonalstructure and shows a first order transition tothe antiferromagnetic phase at 8.95 K [1].Because of the strong single ion anisotropy ofFe2+ ion this compound shows successivemetamagnetic transition under appliedmagnetic field H parallel to the c-axis [2].Wiedenmann et al. [3] have made neutronscattering experiments on FeI2 under H anddetermined the spin structures. In zero field, acommensurate magnetic ordering is defined bythe wave vector k=[1/4, 0, 1/4]. Above thecritical field Hc1 the phase (F1 phase) is amulti-k structure with k1=[1/6, 1/6, 0], k2 =[1/3, -1/6, 0] and k3=[1/6, -1/3, 0]. Above the criticalfield Hc2 the phase (F2 phase) is specified byk1=[1/5, 1/5, 0], k2=[2/5, -1/5, 0], k3=[1/5, -2/5,0] and k0=0. Above the critical field Hc4 thephase (F4 phase) has a single-k with k=[1/5, -2/5, 0]. These authors claim that the phase(F3) at Hc3<H<Hc4 is in a paramagnetic one.This last statement is, in our opinion, strange. From our recent measurements of heatcapacity and magnetization on FeI2 [4], wefound several new phases in H. Moreover, weobtained an evidence for the existence of amagnetic ordering in the phase F3. In order tounderstand more thoroughly the temperature-magnetic field phase diagram of FeI2, we haveperformed neutron scattering experimentsunder high fields using the VM1 magnet. In the phase F1 we found the wave vectork=[1/6, 1/6, 0] as reported before [3]. In thephase F2 we found a hysteretic behaviour inthe wave vector k=[1/5, 1/5, 0]. A new resultobtained in this work is the observation of amagnetic order in the phase F3. Figure 1shows the result obtained at T=5 K. Themagnetic ordering in this phase has a wavevector around [1/5, 1/5, 0] which is fielddependent as shown in Fig. 1. The existenceof a magnetic ordering in the phase F3 isconsistent with the result of our heat capacityand magnetization measurements [4].

Clearly more detailed neutron scatteringexperiments are needed to clarify thisinteresting phase diagram.

Figure 1. Magnetic field dependence of the (h, h,0) Bragg point measured at T=5 K.

References[1] D. Petitgrand et al.; J. Physique-Lett. 41 (1980) L135.[2] A. R. Fert et al; Solid State Commun. 13 (1873)

1219.[3] A. Wiedenmann et al.; Physica B156&157 (1989) 305.[4] H. Aruga Katori and K. Katsumata;unpublished.

0.26

0.24

0.22

0.20

0.18

0.16

0.14

h

14121086420

H (T)

field increasing field decreasing

FeI2 H//c T=5.0 K

29


EXPERIMENTAL REPORT Proposal N° PHY-01-965Instrument E4Disappearance of Antiferromagnetic phase Due

to Random Impurity Effect in CoNb2O6 Local Contact K. Prokes

Principal Proposer: S. Mitsuda, Science University of Tokyo,Japan Date(s) of ExperimentExperimental Team: H. Okano, S. Mitsuda, Science University of

Tokyo, JapanK. Prokes, P. Smeibidl, HMI Berlin

28 Feb– 11 Mar 2001

Date of Report: 30 September 2001

As one of model materials of triangularlattice antiferromagnet with a partially releasedgeometrical frustration, recently we have studiedthe isosceles triangular Ising antiferromagnetCoNb2O6. The system exhibits a complicated H//c-Tmagnetic phase diagram1,2 consisting of variousordered states with propagation wave vector Q = (0q 0) and slow domain-growth-kinetics withanomalously low growth exponent n ~ 0.2 in theantiferromagnetic (AF) phase.3 In this study, weinvestigated how magnetic ordering as well asdomain-growth-kinetics characteristic to anisosceles-triangular geometry of frustrated spinsfound in CoNb2O6 is modified on substitution of asmall amount of Mg2+ none-magnetic impurities.

In this experiment, single crystal of Co1-

xMgxNb2O6(x=0.01) has been prepared by flux-growth method and investigated at E4 with theneutron wavelength 2.44 Å at the temperature downto 0.2 K under applied field up to 4.4 kOe, usingcryomagnet VM2 with dilution stick.

We investigated time-dependence ofscattering profile after a field quench at severaltemperatures below TN2

x=0.00 ~ 2.0K (AF-IC phasetransition temperature of sample with x=0.00).Although in-phase susceptibility decreasedaccording to the power-law with an anomaly lowgrowth exponent n ~ 0.18 (slightly lower than thatof sample with x = 0.00), propagation wave numberq remained to be incommensurate (IC) value ~0.46, and the mean domain size along both a and bdirection did not show the remarkable growth inour observation time. This indicates that only 1%substitution of none-magnetic impurities is enoughto suppress AF domain-growth-kinetics. In Fig. 1,we show the H//c-T magnetic phase diagramdetermined from the (3 k 0) reciprocal-lattice scans.Compared with H//c-T magnetic phase diagram ofsample with x = 0.00,2 several features, such asPM-IC & IC-FR phase transitions, the field-inducedphase transitions between the FR state and thesaturated PM state, existence of magnetic hysteresisand melting of the frozen FR state2 above T ~ 0.6K, are maintained. In short, the system maintainsthe shape of H//c-T magnetic phase diagram ofsample with x = 0.00, except that IC phase replaces

AF phase as low temperature phase, indicating thatthe apparent IC phase at low temperature in samplewith x = 0.01 is thermodynamically equivalent toAF phase seen in the sample with x=0.00. Takingaccount of previous study of domain-growth-kinetics of sample with x = 0.003 as well as ourMonte Carlo simulations, we suggest that theapparent IC state is not simply sinusoidallyamplitude-modulated state, but domain state inwhich thermodynamically equivalent four types ofAF domain, A, B, C, D,3 arrange quasi-regularlyalong the b axis (like A/D/C/B/A/D…) with phaseshift of /2 and their domain-wall-motion isstrongly pinned by small amount of none-magneticimpurities.

Fig. 1. H//c-T magnetic phase diagram. The shadearea shows the hysteresis of phase boundary.

References1S. Kobayashi, S. Mitsuda, M. Ishikawa, K.Miyatani, and K. Kohn, Phys. Rev. B 60 3331(1999).2S. Kobayashi, S. Mitsuda, and K. Prokes, Phys.Rev. B 63, 024415 (2001).3S. Kobayasehi, S. Mitsuda, T. Jogetsu, J.Miyamoto, H. Katagiri, and K. Kohn, Phys. Rev. B60, R9908 (1999).

30


EXPERIMENTAL REPORT Proposal N° PHY-01-1035Instrument E4Field-induced Magnetic phase transition in a

Triangular Lattice Antiferromagnet CuFe0.98Al0.02O2 upto 14.5T Local Contact

K. Prokes

Principal Proposer: S. Mitsuda, Science University of Tokyo,Japan Date(s) of ExperimentExperimental Team: N.Terada, S. Mitsuda, Science University of

Tokyo, JapanK. Prokes, HMI Berlin

28 Aug– 10 Sep 2001

Date of Report: 30 January 2002

Delafossite-type compound CuFeO2 has beenextensively investigated as one of the modelmaterials for the triangular lattice antiferromagnet(TLA).[1-2] In contrast to the non-collinear 3-sublattice ground state in typical Heisenberg spinTLA, CuFeO2 has the 4-sublattice ground state withcollinear magnetic moments along the c-axis, inspite of the Heisenberg spin of orbital singlet Fe3+

magnetic ions with competing exchangeinteractions. Recently, with the aiming indisappearance of quasi-Ising character in CuFeO2,we performed neutron diffraction study ofCuFe0.98Al0.02O2 under zero magnetic field. Then,we found that CuFe0.98Al0.02O2 shows the successivemagnetic phase transitions from the lowtemperature state to a paramagnetic state throughthe intermediate temperature state that is not PDstate with collinear spins along the c-axis [1] buthelical state. As for the low temperature state,although we have not elucidated its magneticstructure yet, it seems to be also complex non-collinear state similar to the first-field-induced stateof CuFeO2 [1]. We have performed present experiment as theextension of the zero field experiment to explorehow quasi-Ising character of the field induced statesof CuFeO2 is destroyed by substitution of a smallamount of Al3+ non-magnetic impurity. A single crystal of CuFe0.98Al0.02O2 prepared bythe floating zone technique was mounted in acryomagnet VM-1 at E4 so as to provide access tothe hexagonal (h k 0) reciprocal lattice zone, withneutron wave length of 2.44 Å. Magnetic field up to14.5T was applied along the hexagonal c-axis. In the low-temperature state, as seen in a typical(h h 0) scan shown in fig.1-(a), weak magneticBragg reflections assigned as (2q 2q 0) and (1-2q 1-2q 0) were observed, where the wave numberq~0.21 is almost independent of temperature andmagnetic field. In the intermediate temperature state, as seen in atypical (h h 0) scan shown in fig.1-(b), no magneticsignal is seen in a (h k 0) zone. In the field induced state, as shown in fig.1-(c)four magnetic Bragg reflections assigned as (1-4q1-4q 0), (2q 2q 0), (1-2q 1-2q 0) and (4q 4q 0) were

observed in a (h h 0) scan, suggesting that a tinyanomaly seen at H~10.5T in the magnetizationcurve of CuFe0.98Al0.02O2 sample is certainlycorresponding to a magnetic phase transition. In conclusion, the field induced phase transitionswith quasi-Ising character (4-sublattice 5-sublattice-like 5-sublattice) in CuFeO2 areentirely modified by substitution of a small amountof Al3+ non-magnetic impurity. The first-fieldinduced state of CuFe0.98Al0.02O2 has the morecomplex helical magnetic structure reflectingHeisenberg character.

Fig.1 Typical diffraction profiles

References[1] S. Mitsuda, M. Mase, K. Prokes, H. Kitazakwa,and H.Aruga Katori: J.Phys.Soc. Jpn. 69(2000)3513[2] O. A. Peterenko, G. Balakrishman, M. R.Lee, D. McK. Pail and A. Hoser: Phys. Rev. B62(2000) 8983

31


EXPERIMENTAL REPORT ProposalN°PHY-01-1031Instrument E4Neutron-diffraction study of field-induced

transitions in Ce2RhIn8 Local Contact K.Prokes,E. Garcia-Matres

Principal Proposer: Evagelia Moshopoulou, NCSR Demokritos, J.L. Sarrao, Los Alamos National Lab. Date(s) of Experiment

Experimental Team: E. Moshopoulou, NCSR DemokritosKarel Prokes, HMIElvira Garcia-Matres, Univ. Augsburg

Oct. 28-Nov 13, 2001

Date of Report: 11 February 2002

Accepted for publication in Physica B(proceedings of the Euroconference “Propertiesof Condensed Matter Probed by X-ray andNeutron Scattering”)

Neutron-diffraction study of field-induced

transitions in the heavy-fermion compound

Ce2RhIn8

E. G. Moshopouloua*, K. Prokesb, E. Garcia-Matresb, P. G. Pagliusoc, J. L. Sarraoc, and J. D.Thompsonc

aNational Center for Scientific Research“Demokritos”, Institute of Materials Science,15310 Agia Paraskevi, GreecebHahn-Meitner-Institute, SF-2, GlienickerStrasse 100, D-14109 Berlin, GermanycCondensed Matter and Thermal Physics, LosAlamos National Laboratory, MS K764, LosAlamos NM 87545, U.S.A.

Abstract We present neutron diffraction measurementsin high magnetic fields (0 to 14.5 T) and at lowtemperatures (2.5, 2.3, 0.77 and 0.068 K) onsingle crystals of the tetragonal heavy fermionantiferromagnet Ce2RhIn8. For B//[110] thefield dependence of selected magnetic andnuclear reflections reveals that the materialundergoes several transitions, the temperaturedependence of which suggests a complex B-Tphase diagram. We present the evolution of theintegrated intensities of selected reflections anddiscuss the associated field-induced transitions.

Fig. 1. Magnetic field dependence of the integratedintensity of the magnetic peak (1/2,1/2,1) at (a) 2.5K, (b) 2.3 K, (c) 0.77 K and (d) 0.068 K.

0 2 4 6 8 10 12 14 16100

200

300

400

-20

0

20

40

60

50

60

70

80

90

100

150

200

250

(d)0.07 K

B (T)

(a) 2.5 K

(b)2.3 K

(c)0.75 K

Inte

grat

ed In

tens

ity (a

rb. u

nits)

32

EXPERIMENTAL REPORT

Investigation of the Magnetic Structure of PrO2


Instrument E4

Local Contact

K. Prokes, E. Garcia-Matres


30. 07. - 09. 08. 2001

Principal Proposer: A.T. Boothroyd, Oxford University, United Kingdom

Experimental Team: C.H. Gardiner, Oxford University, United Kingdom,

A.T. Boothroyd, Oxford University, United Kingdom


Introduction

Recent neutron scattering measurements on

PrO2 have found evidence for strong magnetoe-

lastic eects [1], and this has prompted us to

make a thorough investigation of the magnetic

structure. The crystal structure is cubic uo-

rite, and antiferromagnetic ordering is obtained

below TN = 14 K. The ordering is known to be

type-I with a wavevector of (100). However, un-

der ambient conditions, it is likely that several

symmetry-equivalent magnetic domains coexist,

which means that data taken under these con-

ditions can be described equally well by each of

the multi-k structures shown in gure 1.

1k 2k 3k

Figure 1: Possible multi-k structures.

To distinguish between these structures, we

must in uence the populations of the domains

so that one is preferred over the others. Here we

describe an experiment in which we attempt to

achieve this by use of a magnetic eld.


The single crystal used in this experiment was

grown by a hydrothermal procedure, and had a

mass of 1 mg. It was oriented with the (011)

direction vertical (parallel to the applied eld).

We were able to access ve magnetic Bragg re-

ections at (100), (011), (211), (122) and (300),

and these were each scanned by crystal rotation

(!-scan) at T = 1:5 K in applied elds of B = 0,

0.5, 1, 2.5 and 5 T. Each time the magnetic eld

strength was altered, the crystal was warmed to

20 K (above TN), then cooled back to 1.5 K

in the new eld.

We found that applied elds of 0.5 and 1 T

produced no signicant change in the intensities

of the magnetic Bragg peaks observed at zero

eld. If the structure of PrO2 were 1k or 2k,

and the applied eld large enough to induce a

single-domain state, we would expect to see a

change in the intensities of the peaks. However,

if the structure were 3k, we would expect no

change, since the 3k structure has only one pos-

sible magnetic domain.

At a eld of 2.5 T the intensities of the (100),

(211), and (300) peaks were unchanged, but

those of the (011) and (122) peaks were reduced.

These observations do not appear to be consis-

tent with the expected intensity changes for the

1k or 2k structures, so we speculate that they

are due instead to a re-orientation of the spins,

directly caused by the applied magnetic eld.

When we applied a eld of 5 T we observed

an unexpected increase in the intensities of all

the peaks by a factor of 1.8. On removal of

the eld the increased intensities persisted. We

found that the only way to regain the original

intensities was to heat to 125 K before cooling

down again.

We conclude that we have obtained data sug-

gestive of (i) a 3k magnetic structure at applied

elds of 1 T, (ii) spin re-orientation at elds

of > 1 T and (iii) an irreversible transition to a

new phase at a eld between 3.5 and 5 T.

References

[1] A.T. Boothroyd et al., Phys. Rev. Lett. 86,

2082 (2001).

33

cnr

EXPERIMENTALREPORTTitle

Name(s) Affiliation

Proposal Nº

Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

Field-induced magnetic structures in UNiGeE4

K. Prokes

EF

K. Prokes HMI

K. Prokes HMI January-March 2001

20.1.2002

UNiGe belongs to an isostructuralgroup of UTX compounds (T = transitionmetal, X = p-element) that crystallize in theorthorhombic TiNiSi type of structure (s.g.Pnma) [1]. The nearest neighbour uraniumatoms form zig-zag chains running along thea axis with an amplitude of about 0.1 cparameter. UNiGe undergoes twoantiferromagnetic transitions at 50 and 42.5K, and it exhibits an easy-planemagnetocrystalline anisotropy with the hard-magnetization direction along the a axis [1]

The ground-state AF structure ischaracterized by a propagation vector (0, 1/2,1/2). At 4.2 K, there are two field-inducedtransitions at 17 and 25 T for the b axis and at3 and 10 T for fields along c (fig. 1). Notransitions are observed for the a//Borientation up to 38 T. While the intermediatefield-induced phases for both b//B and c//Bgeometries have propagation vector (0, 1/3,1/3), the INC structure is characterized by a

propagation vector (0, δ1, δ2).

In this experiment we determined thelast unknown phase: the field induceduncompensated antiferromagnetic structureFIUAF with field applied along the b axis. At43 K, the critical field at which transitionINC →FIAUF occurs amounts to 5.5 T, i.e.field that is reachable with the HM-1 magnet.At 6 T we obtained magnetic moments of0.7 µB/U forming complicated arrangement.

Schematic representation of thecommensurate phases is given in fig. 2.Interestingly, all the phases exhibit acomplicated non-collinear arrangement of Umoments with all three components, i.e. alsoalong the a axis, which is the hard-magnetization direction. The field-forcedferromagnetic phase, which is established forc//B above 10 T still exhibits significant aaxis component similar to the low-fieldphases. This suggests that the magneticordering in UNiGe is governed by anisotropicexchange interactions.

This work was presented at ICNS\01.Reference[1] V. Sechovský and L. Havela: FerromagneticMaterials, ed. K.H.J. Buschow, (North Holland,Amsterdam 1998) vol. 11 and references therein

34


Name(s) Affiliation

Proposal Nº

Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

Magnetic structure in UCuGe single crystalE4

K. Prokes

EF

K. Prokes HMI

K. Prokes HMIA.V. Andreev DES, Charles University, Prague

January-December 2001

25.1.2002

UCuGe crystallizes in the hexagonalCeCd2 type of structure (s.g. P-3m1) [1] andwas studied up to now only in apolycrystalline form. U, Cu and Ge atomsoccupy 1(a), 1(d) and 1(f) sites, respectively.UCuGe is reported to exhibit a cantedantiferromagnetic (AF) structure of Umagnetic moments of 2.0 B (at 4.2 K) below50±3 K The magnetic moments are alignedperpendicular to the trigonal axis. In the basalplane they make an angle of 60 with the a-axis, whereas the moments in the plane withz = 1/2 are turned by 90 with respect to thedirection of moments in the plane with z = 0.

Recently, single crystal becameavaliable, that we investigated at E4 in zeromagnetic field.

0 10 20 30 40 50 600

100

200

300

400

500

600

0 10 20 30 40 50 60 70

27500

28000

28500

29000

I (C

ount

s)

T (K)

(1 1 0)

Inte

nsity

(Cou

nts)

T (K)

(0.5 0 1)

Fig. 1: Temperature dependence of (3/2 0 1)and (1 1 0 ) reflections in UCuGe.

We have collected data in two geometries. Inthe first one was the crystal oriented in the a-c plane, in the other in b-c plane. Refinementof the paramagnetic intensities led toconclusion that UCuGe orders in the orderedversion of the CeCd2 type of structure asindicated in the literature [1].

As the temperature is lowered belowthe magnetic phase transition, new reflectionthat can be indexed by four AF propagationvectors (1/2, 0, 0), (1/2, 1/2, 0), (1/2, 0, 1/2)and (1/2, 1/2, 1/2), appear. On top of that,intensity of some of the nuclear reflectionsincrease as well (see fig. 1).

The full refinement turned to bedifficult and is not fully finished. However,preliminary calculations suggest a goodagreement with previous poder data [1].However, the question arises whether the AFstructure of UCuGe is multi-q or single-q.We could not answer this question becausethe intensities of equivalent reflections arewithin the error bars equal. To answer such aquestion one needs to apply an externalperturbation like a magnetic field to influencethe domain population (in the case thereexists one). Indeed, magnetizationmeasurements with fields along the a or baxes indicate a step-like increase of themagnetic susceptibility suggesting domainrepopulation. This will be the subject offurther studies.

Reference[1] J. Leciejewicz et al. J. Magn. Magn.Mater. 97 (1991) 219

35


EXPERIMENTAL REPORT Proposal N° *Instrument E4Search for Field-Induced Magnetic Order in

Superconducting Bi2Sr2CuO6+x Local Contact K. Prokes,M. Garcia-Matres

Principal Proposer: B. Keimer, Max-Planck-Institut Stuttgart Date(s) of ExperimentExperimental Team: S. Bayrakci, Max-Planck-Institut Stuttgart

C. Ulrich, Max-Planck-Institut StuttgartB. Liang, Max-Planck-Institut Stuttgart

12.11.01 – 18.11.01


The original experiment proposed wasa search for field-induced magnetic order inYBCO. However, since this sample becameunavailable and since exciting recentdevelopments were reported on a relatedsystem, an alternate experiment wasperformed. Using the 14.5T cryomagnet, wesearched for magnetic-field-induced magneticsuperstructure in a single-layer copper-oxidesuperconductor: La-substituted Bi2Sr2CuO6+x.

Bi2Sr2CuO6+x is identical to the well-known bilayer high-Tc copper oxideBi2Sr2CaCu2O8+x in crystal structure, exceptwith respect to the number of copper-oxidelayers per unit cell. Recently, a field-inducedincommensurate charge modulation wasdetected by STM around magnetic vortices onBi2Sr2CaCu2O8+x (J. E. Hoffman et al., Science295, 466). The purpose of the experiment wasto search for an incommensurate spinmodulation associated with this charge-ordered state. Bi2Sr2CuO6+x was chosenbecause the single-layer structure makes thescattering geometry more straightforward, andbecause a larger signal can be expected dueto the lower superconducting transitiontemperature.

In this experiment, we utilized a singlelarge La-substituted Bi2Sr2CuO6+x crystal withTc~20K, grown using a floating-zone furnace.We searched for magnetic superstructure inthe superconducting CuO2 planes, with themagnetic field applied perpendicular to theplanes.

We began the experiment with asystematic investigation of the (hk0) scatteringplane. Qh-scans from 0.3 – 0.9 r.l.u. at Qk =0.5 r.l.u. and T = 1.8K revealed noenhancement of scattering intensity uponapplication of a 14.5T magnetic field. Diagonalscans within the (hk0) plane, however, showeda possible enhancement of intensity withapplication of the magnetic field at (0.61, 0.39,0) r.l.u., significant at the level of 2.8 (seefigure). A similar field-induced intensity at thelevel of 2.4 was observed at (1.61, 1.39, 0),

an equivalent point in a higher Brillouin zone.This would not be expected if the field-inducedintensity at (0.61, 0.39, 0) r.l.u. were due tospurious processes. However, since otherequivalent points have not yet shown asignificant field-induced enhancement, ourresults at present are still inconclusive. Tofollow up on these promising results and toimprove our statistics, we are at the momentpreparing a sample of larger volume,composed of multiple co-aligned crystals. Wehope to have the opportunity to perform anexperiment with such a sample in the future.

0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70-300

-200

-100

0

100

200

300

400

500

Diagonal elastic scan: (Q H, Q K = 1-Q K, 0)

La-substituted B i2Sr2CuO 6+x

T = 1.8K

cou

nts(

B=1

4.5T

)-co

unts

(B=0

T),

per

2 h

ours

Q H (r.l.u.)

36

EXPERIMENTAL REPORT Proposal N° PHY-01-973Instrument E5Structural and Magnetic Instabilities of

La2-xSrxCaCu2O6 Local Contact A. Loose

Principal Proposer: C. Ulrich, Max-Planck-Institut FKF, Stuttgart Date(s) of ExperimentExperimental Team: M. Reehuis, Universität Augsburg

B. Keimer, Max-Planck-Institut FKF, StuttgartM. Ohl, FZ-Jülich; ILL, Grenoble

15.1.2001 – 4.2.2001


A neutron diffraction study of a nonsuperconducting La1.8Sr0.2CaCu2O6 singlecrystal, a bilayer copper oxide without CuOchains, has revealed an unexpected tetragonalto orthorhombic transition. The predominantstructural modification below the transition is anin plane shift of the apical oxygen. Theorthorhombic superstructure is stronglydisordered, and a glassy state involving bothmagnetic and structural degrees of freedomdevelops at low temperature.A single crystal of La1.8Sr0.2CaCu2O6 (3 x 3 x 3mm3) was grown by the travelling floating zonetechnique. Neutron diffraction experiments werecarried out on the four-circle diffractometer E5 atthe HMI. The data were collected with a two-dimensional position sensitive 3He-detector. Forthe data collection at 10 K a closed cyclerefrigerator has been used. Two data sets ofLa1.8Sr0.2CaCu2O6 with a total of 623 (259unique) and 791 (256 unique) reflections werecollected at 295 K and 10 K, respectively. Theused neutron wavelength was = 0.889 Å.Excellent structure refinements of the roomtemperature data could be obtained using thetetragonal space group I4/mmm. The results ofthe refinements are given in Table 1.At 10 K additional reflections with very weakintensities were found. All these peaks could beindexed as (h/2, k/2, ) with h, k odd and evenbut with 0, indicating a doubling of the unitcell. Due to the fact that these reflections areobservable up to large 2-values and the factthat the copper moments are expected to berelatively small, the superstructure reflectionscan be assumed to be not magnetic. The dataanalysis showed that the crystal structure couldbe refined in the orthorhombic space groupBmab (No. 64, standard setting Cmca) (Table 1).The transition into the orthorhombic phase isprimarily caused by the shift of the apical O2atoms along the tetragonal (110) direction ofabout 0.05 Å.The space group Bmab does not allow thepresence of reflections (1/2, 1/2, ) with beingodd. The presence of these reflections at 10 K,

especially at low 2-values, indicates thepresence of magnetic order of the coppermoments. In addition, these reflections showa sinusoidal intensity modulation as afunction of that extinguishes the reflectionwith = 0. A similar modulation is observedin antiferromagnetic YBCO and is known toarise from strong antiferromagnetic interlayerexchange within a bilayer unit. The onsettemperature of the magnetic reflections isidentical to the structural transitiontemperature within the experimental error.

Table 1:Positional parameters of La1.8Sr0.2CaCu2O6at 10 K and 295 K from single-crystalneutron diffraction. For the refinements ofthe 10 K data the occupancies of the atomswere taken from refinements of thetetragonal structure and were not allowed tovary.

Atom y z pop295K I4/mmm a,b=3.7974(4) Å c=19.3138(19) ÅLa/Sr 4e 0 0.17600(9) 0.90(3)Ca 4e 0 0.17600 0.10(3)Ca 2a 0 0 0.83(3)La/Sr 2a 0 0 0.17(3)Cu 4e 0 0.41447(9) 1.0O1 8g 0.25 0.08203(8) 1.000(14)O2 4e 0 0.29639(14) 1.012(17)10K Bmab a,b=5.3621(5) Å c =19.2436(19) ÅLa/Sr 8f -0.0009(3) 0.17575(11) 0.90Ca 8f -0.0009 0.17575 0.10Ca 4a 0 0 0.83La/Sr 4a 0 0 0.17Cu 8f 0.0002(3) 0.41474(11) 1.0O1 8g 0.25 0.08210(9) 1.0O1’ 8g 0.25 0.9183(4) 1.0O2 8f 0.0094(5) 0.29634(17) 1.01

37


EXPERIMENTAL REPORT Proposal N° PHY 01-1040

Instrument E5Crystallographic and Magnetic structureof YVO3 Local Contact

A. Loose, M. Reehuis

Principal Proposer: C. Ulrich, Max-Planck-Institut FKF, StuttgartExperimental Team: M. Reehuis, Universtität Augsburg

C. Ulrich, Max-Planck-Institut FKF, StuttgartB. Keimer, Max-Planck-Institut FKF, Stuttgart

12.8.2001 – 10.9.2001


Among the transition metal oxides withperovskite structure YVO3 is of particularinterest because it undergoes reversible signchanges in the magnetization with temperature[1]. YVO3 has two magnetic phases, a C-typephase between 114 K and 78 K and a G-typephase at low temperatures [1,2]. The magneticphase transition at 78 K is accompanied by astructural phase transition, while no structuralphase transition occurs at 114 K [2,3].

Previously we have studied the spin wavedispersion relation of the Mott-Hubbardinsulator YVO3. Our inelastic neutronscattering results indicate that the hightemperature magnetic phase has an unusualspin fluctuation spectrum that cannot beunderstood within a conventional spin wavetheory. This may indicate a ground state withstrong quantum fluctuations [4], analogous tothe situation in LaTiO3 [5], where no orbitalordering is observed. In the low temperaturephase of YVO3 on the other side aconventional spin wave spectrum is found,which is suggestive for a ground state with wellestablished orbital order. In order to develop atheory for the full understanding of themechanisms behind the effects of orbital orderand orbital fluctuations in YVO3, the preciseknowledge of the magnetic structure isnecessary.

Since to the best of our knowledge, the spindirection is not precisely known in both phases[1,2], we have performed a single-crystalneutron diffraction experiment on the four-circle diffractometer E5. The data of YVO3were collected at 10 K, 85 K, and 130 K usingthe wavelength = 2.38 Å. The crystalstructure in the paramagnetic range could berefined with the orthorhombic space groupPbnm, but the presence of additionalsuperstructure reflections indicates a lowersymmetry. The magnetic contributions of thereflections finally have been determined fromthe differences F10K

2–F130K2 and F85K

2–F130K2.

At 10 K relatively strong magneticintensities have only been observed on the

reflections (101) and (011). These reflectionsare only allowed, when the magnetic momentsof the four V-atoms (Wyckoff position 4a) areordered with the spin sequence G( – – ).Due to the fact that the magnetic intensities ofthe reflections (101) and (011) areapproximately the same, the moments must bealigned parallel to the c-axis. The value of theobtained magnetic moment is 1.72(5) B/V-ion.

With increasing temperature, the magneticintensities of (101) and (011) decreaseabruptly at 77 K. The remaining relatively weakmagnetic intensity of these reflectionsvanished finally at 117 K. On the other side,the intensities of the reflections (100) and(010) increase spontaneously at 75 K. Fromthe structure refinement of the data collectedat 85 K we obtain a reduced compound of themagnetic moment along the c-axis (G-type) ofexp,z=0.30(4) B and a spin sequence C( ––) along both the x- and y-axis with a magneticmoment of exp,x=0.49(3)B andexp,y = 0.89(2)B, respectively (see figure below). The totalmagnetic moment is exp=1.05(2)B.

[1] Y. Ren, et al., Nature 396, 441, Dec. 1998;[2] H. Kawano, H. Yoshizawa, and Y. Ueda, J.Phys. Soc. Japan 63, 2857 (1994).[3] G.R. Blake, et al., Phys. Rev. Lett. 87, 245501(2001).[4] G. Khaliullin, P.Horsch, and A.M. Oles, Physs.Rev. Lett. 86, 3879 (2001). [5] B. Keimer, et al., Phys. Rev. Lett. 85, 3946(2000); G. Khaliullin and S. Meakawa, Phys. Rev.Lett. 85, 3950 (2000).

a b

c

38

EXPERIMENTAL REPORT

Eects of Fe Additions on the Helix

SpinStructure of the Metamagnetic Compound

MnAu2


Instrument E6

Local Contact

N. Stuer


26. 6. - 2. 7. 2000

9. 7. - 13. 7. 2001

Principal Proposer: Ulrich K. Roler, IFW Dresden

Experimental Team: A. Kreyig, IAPD, TU Dresden

U.K. Roler, IFW Dresden

N. Stuer, HMI Berlin


The helimagnet MnAu2 shows a remarkable

giant magnetoresistance above its metamagnetic

threshold eld. Recently, we found that Fe-

substitution causes drastic changes of its mag-

netic properties inducing a behaviour macro-

scopically similar to ferromagnetism [1]. Neu-

tron diraction experiment was employed to

investigate the microscopic spin-structure in

Fe(Co)-substituted samples. The samples were

polycrystalline, melt-spun and annealed ribbons.

According to X-ray diraction results the sam-

ples were single-phase MnAu2 structure (space

group I4=mmm). This was corroborated by the

neutron diraction. Measurements were done

at the E6-diractometer equipped with a cry-

ofurnace (OF1 T 3 K to 500 K). Samples

(about 3-5 g) were pressed into a V-tube sample-

holder (=6 mm, l=5 cm). Fig. 1 shows a

representative diraction pattern for the parent

compound. Temperature scans were done dur-

0

100

200

300

400

500

600

700

800

10 20 30 40 50 60 70 80 90

Inte

nsity

[Cou

nts]

2θ [DEG]

MnAu2

(002

)(0

02)-

(002

)+

(101)

(101

)-

(101

)+

(110

)(0

04)-

(103

)-(1

03)

(004

)(1

12)-

(112

)(1

03)+ (0

04)+

(112

)+

T=3.4K

Figure 1: Neutron powder diraction scan for

pure MnAu2. Magnetic satellite peaks due to the

helix spin-structure peaks are indexed (h; k; l).

ing heating for (Mn1xFex)Au2 (x=0, 0.01, 0.02,

0.05, 0.075). Assuming an axial XY-helix with

moments in the tetragonal plane and single-K

propagation vector, we evaluate K = (0; 0; ")

(Fig. 2) displaying a strong dependence on Fe-

contents x and "(T ) increasing for x < 0:02, non-

monotoneous for x = 0:02, and decreasing for

x = 0:05. For x = 0:075 no satellites correspond-

0

0.1

0.2

0.3

0 50 100 150 200 250 300 350 400

ε in

prop

agat

ion

vect

or (0

0 ε)

T[K]

Mn1-xFexAu2

x=0

x=0.01

x=0.02

x=0.05

Figure 2: Propagation vector for helix spin-

structure vs. temperature in Fe-substituted

MnAu2 from positions of (002)-peaks.

ing to a helix could be found down to 2.5 K, in-

stead magnetic scattering contributions on main

Bragg-peaks reveal a ferromagnetic order with

Curie temperature Tc400 K. For x = 0:05, at

TN150 K the helix disappears and is replaced

by ferromagnetic order with Tc380 K. In both

ferromagnetic structures the moments are in the

(002) planes. For comparison, similar measure-

ments were performed on (Mn0:95Co0:05)Au2 be-

cause Co-substitution only modies the helimag-

netism of the parent compound [1]. For MnAu2and Mn0:98Fe0:02Au2 measurements in a mag-

netic eld up to 5 T (VM3) could be performed

at a few temperatures providing a consistency

check: the satellite peaks disappear in the eld-

range of the helixfan transition found in mag-

netization measurements.

[1] A. Handstein et al., J. Appl. Phys. 87, 5789

(2000).

39


EXPERIMENTAL REPORT Proposal N° PHY-01-975Instrument E6Neutron Diffraction Study of a Single-

Crystalline UCu5Al Sample Local Contact Stuesser N

Principal Proposer: V.H. Tran, R. Troć, T. Komatsubara, Inst. Low. Temp. andStruc. Res.,PAS, Wrocław Date(s) of Experiment

Experimental Team: V.H. Tran, Inst. Low. Temp. and Struc. Res.,PAS, WrocławN. Stuesser, HMIM. Hofmann, HMI

28.01-3.02.01


UCu5Al is a recently discovered heavy-fermion that orders antiferromagnetically withan incommensurate ordered wavevector q =(0, 0, 0.55) and a moment of 1.4 B/U atomalong the tetragonal c-axis [1,2]. However,recent measurements on IN22 (ILL-Grenoble)with a large crystal have shown that thepublished magnetic structure is wrong [3].There was observed by Lander et al. anintensity at Q positions along the [001] axis,suggesting that the magnetic structure ofUCu5Al may involve a cycloid or the uraniummoment possesses a component lyingperpendicular to the c-axis. The goal of thisexperiment was to collect magnetic intensitiesin order to test possible models for magneticstructure of UCu5Al.

Our experiment was carried out on thesame single-crystalline sample, as was usedon IN22 spectrometer. Using a wavelength of = 2.447 A, we oriented the crystal along the[002] direction at 12 K, and next along [200]and [002] at 1.6 K (Fig.1).

The positions of nuclear peaks (002) and (200)correspond to the lattice parameters a = 6.356and c = 4.914 A. These parameters areconstant in the temperature range 1.6 - 12 K.

Based on the reported magneticstructure with q = (0,0, 0.55) [2], we expectedmagnetic reflection (101-) at = 72.7 and 2 =25.7 and (200+) at = 94.5 and 2 = 48.2.Indeed, at 1.6 K we found (101-) at 2 = 25.75

and (200+) at 48.45. These positions allow todetermine wavevector of ~ ql = 0.562-0.576. Infact, this vector does not differ significantlyfrom the earlier reported value (0.55). Theobserved magnetic intensities of the reflections(101-) and (200+) yield the magnetic momentsto be about 0.95 and 1.65 B/U, respectively.At 12 K, the propagation vector is the same,but the magnitude of magnetic moments isslightly reduced to about 0.76 and 1.62 B/U,respectively (Fig. 2).

Information from [3] suggests that weshould observe following magnetic reflections:(000) at = 8.1 and 2 = 16.3, (001-) at =6.1 and 2 = 12.3, (002-) at = 20.8 and 2 =41.7, and (001+) at = 23 and 2 = 46.6.Therefore, we carefully performed scan aroundthe positions given above. However, we didnot observe any magnetic signal resulting froma perpendicular direction of moments to the c-axis (up to 2% of the strongest magneticreflection). Thus, we conclude that the neutrondata collected on a single-crystalline sample ofUCu5Al confirm the incommensurate structurewith (q = 0,0,0.57) and with uranium momentsparallel to the tetragonal c-axis.

[1] R. Troć et al. JMMM 183, 132 (1998).[2] R. Troć et al. JMMM 190, 251 (1998).[3] G.L. Lander et al. Experimental Report ILL,No: 4-03-1099.

24.0 24.5 25.0 25.5 26.0 26.5 27.0

-50

0

50

100

150

200

250

300

1 0

1

1.6 K 12 K Fits

UCu5Al SCk = 0 0 0.565

2 (degrees)

Inte

nsiti

es (a

rb. u

nits

)

40


EXPERIMENTAL REPORT Proposal N° PHY-01-977t

Instrument E6Magnetic and crystallographic order inUPd1.85Sn Local Contact

Ralf Feyerherm

Principal Proposer: I. Maksimov, Inst. Für Metallphysik, TUBraunschweig, Germany Date(s) of Experiment

Experimental Team: I. Maksimov, S. Süllow, Inst. f. Metallphysik, TU BraunschweigR. Feyerherm, HMI

21.05.01 – 25.05.01


The heavy fermion compound UPd1.85Sn exhib-its, instead of the metallic resistivity and non-magnetic ground state of the parent compoundUPd2Sn, a negative resistive slope d/dT andantiferromagnetic ordering below TN=28K [1-3].In addition, the crystal structure changes fromorthorhombic Pnma for UPd2Sn to a cubic Fm3mHeusler structure for UPd1.85Sn [2,3]. Presently,we study the role the Pd vacancy disorder playsfor the transport and thermodynamic propertiesof UPd2-xSn. As part of this project, and to verifymagnetic ordering and to determine its type wecarried out neutron diffraction experiments onUPd1.85Sn. A polycrystalline sample UPd1.85Sn was preparedby arc-melting the constituents in stoichiometricratio under Ar atmosphere, and which was sub-sequently powderized. The neutron diffractionexperiment has been performed on the instrumentE6, using a neutron wavelength =2.448Å, attemperatures ranging from 2-32K. Typical data are presented in Fig. 1a, where weplot the measured neutron intensity on a log scaleas function of 2 at T=2K. After subtraction ofthe structural scattering intensity (measured at32K, not shown) we obtain the magnetic differ-ence spectrum I2K-I32K, which is shown in Fig.1b. Two magnetic reflections at 2= 30 and 48are observed, as indicated by arrows.

Fig. 1: a.) Neutron diffraction spectrum ofUPd1.85Sn, taken at T=2K, and b.) the differencespectrum I2K-I32K.

Full Rietveld structure refinements of the dif-fraction data were carried out employing theWinPLOTR/FULLPROF program. Refinementof the structural data at T=32K with the fullyordered Heusler lattice (Fm3m, no site exchange)and nominal Pd offstoichiometry yields a latticeparameter a = 6.744(4)Å with RBragg = 3.4%. Inaddition, a refinement of the magnetic intensityyields a wave vector [000] with an ordered mag-netic moment ord=0.97(9)B at T=2K. The twomagnetic peaks detected in the difference spec-trum (Fig. 1b) correspond to the (110) and (210)reflection of this structure and fit an orderingwave vector of (000). We determined the tem-perature dependence of the magnetic (110) re-flection, which is depicted in Fig. 2. The sup-pression of magnetic order at TN=27K is observ-able, in agreement with the thermodynamic data

[2,3].Fig. 2: Temperature dependence of the magneticmoment ord. The solid lines is a guide to the eye.

[1] C.Rossel et al., Solid State Commun. 60(1986) 563

[2] S.Süllow et al., Physica B 230-232 (1997)43-45

[3] I. Maksimov et al., Physica B, in print (2002)

10000

100000

30 40 50 60

0

5000

b.

a.T=2K

Inte

nsity

(tot

al c

ount

s)

I 2K-I 32

K

2 (Deg)

0 5 10 15 20 25 30 35

0.0

0.2

0.4

0.6

0.8

1.0

or

d (

B)

Temperature (K)

41

EXPERIMENTAL REPORT Proposal N° PHY-01-978Instrument E6Magnetic Instability in RCo3 IntermetallicsLocal Contact N. Stuesser

Principal Proposer: E. Gratz, Vienna Technical University Date(s) of Experiment

Experimental Team: A. Hoser, RWTH – AachenA.S. Markosyan, Moscow State University

22.1.01 – 26.1.01


The RCo3 compounds crystallise in the rhombohedralPuNi3-type structure with two R-crystal sites (RI: 3aand RII: 6c) and three Co-sites (CoI: 3b, CoII: 6c andCoIII: 18h). In YCo3 two metamagnetic transitionshave been observed, at 60 T (weak to intermediateferromagnetism) and at 82 T (intermediate to strongferromagnetism) [1]. When Y is replaced by amagnetic rare earth, the whole Co sublattice becomesadditionally magnetised due to the strongintersublattice molecular field HRCo. In some RCo3compounds, where the Co sublattice is in the strongmagnetic state at low temperatures, a temperatureinduced change of the Co moments is expected at acertain critical temperature TTR. This is due to thedecrease of HRCo with increasing temperature.However, this transition should also affect themagnetisation of the rare earth sublattice.

The aim of this project was to evaluate thetemperature variation of the Er and Co sublatticemagnetisations in ErCo3 (TC = 402 K), for which theabove mentioned temperature induced transition inthe Co sublattice was expected [2]. The diffractionpatterns were analysed by a FULLPROF program.

The diffraction patterns on a polycrystallinesample of ErCo3 were recorded at differenttemperatures with the E6 neutron spectrometer. Thetemperature dependence of the hexagonal unit cellvolume, Vel, of ErCo3 is given in the figure.

As can be seen, below 100 K a pronouncedchange of Vel exists. This anomaly in Vel(T) is closelyrelated to a change of the magnetisation of the Cosublattice. It is assumed that below TTR 100 K HRCoexceeds 82 T, and the increasing magnetisation of theEr sublattice transfers the Co sublattice from theintermediate into the strong ferromagnetic state.

The analysis of the neutron data revealed thatthe magnetic moment on the CoI sites, µCoI, hardlychanges below 200 K (about 1 B/Co). µCoII is about1.1 B/Co in the range 100 – 200 K and increases upto ~1.7B /Co at 2 K. Similarly, µCoIII sharply growsfrom 0.5 B/Co at 125 K up to ~1.3 B/Co at 2 K.However the neutron experiment also showed thatthe magnetic moments on both Er-sites exhibit a step-like increase when cooling below TTR.

This fact might explain why the transition at100 K is practically not observable in the temperaturedependence of the spontaneous magnetisation, sincethe magnetisation changes in both sublattices cancelout each other because of their antiparallelorientation. A macroscopic parameter such as theunit cell volume, which is sensitive to the magneticstate of the Co sublattice (intermediate versusstrong ferromagnetism) only, clearly shows aninfluence.

The present study revealed that mainly theCoII and CoIII sites are responsible for the


Temperature dependence of Vel of ErCo3.

transition occurring between the intermediate (T >TTR) and strong ferromagnetic (T < TTR) states inthe Co sublattice of ErCo3.

References[1]T. Goto, H. Aruga Katori, T. Sakakibara and M.

Yamaguchi, Physica B 177 (1992) 255.[2]N. Ali, I.S. Dubenko, I.Yu. Gaidukova, A.S.

Markosyan and V.E. Rodimin, Physica B281&282 (2000) 696.

0 100 200 3001570

1575

1580

1585

1590

ErCo3

Cooling Heating

V [Å3]

T [K]

42


20 30 40 50 60 70 80 90

-1000

0

1000

2000

3000

I = I274 K-I302 K

Ho2Co15Si2

I274 K

(216) (116)(325) (125)

(113)(213)

(003)(110)(210)

I (co

unts

)

2 (deg)


Instrument E6Magnetic structure of Ho2Co15Si2Local Contact N. Stüßer

Principal Proposer: Y. Janssen, Universiteit van Amsterdam Date(s) of ExperimentExperimental Team: N. Stüßer, HMI Berlin

19/03/2001-26/03/2001


In a recent article [1], we reported on the magneticproperties of a single-crystalline sample of theferrimagnetic pseudobinary compound Ho2Co15Si2.The crystal structure is the rhombohedral Th2Zn17-type of structure. The Curie-temperature is TC =837 K, below which ferrimagnetic order with theHo and Co magnetic moments ordered antiparalleloccurs. Between TC and TSR ~ 320 K, the easymagnetization direction is the c-axis, i.e. themoments are aligned along the c-axis. At atemperature near 320 K, a spin-reorientationtransition takes place, leading to an easymagnetization direction perpendicular to the c-axis.This spin-reorientation transition is ascribed tocompeting magnetic anisotropies of the Ho and Cosublattices. Above TSR, 320 K, the magneticanisotropy is dominated by the Co sublatticeanisotropy, favoring an easy-axis configuration.Below TSR, the magnetic anisotropy is dominatedby the Ho sublattice anisotropy, favoring an easy-plane configuration. Upon further lowering thetemperature, the Ho ordered magnetic momentsincrease, and near 30 K compensate the antiparallelordered Co magnetic moments.The focus of this work lies with the spin-reorientation transition near 320 K. We performedmagnetization experiments on our single-crystalnear the spin-reorientation transition temperature[1]. The saturation magnetization with the fieldapplied along the c-axis is higher (by about 0.6B/f.u.) than with the field applied perpendicular tothe c-axis. This magnetization anisotropy occursboth above and below the spin-reorientationtemperature, thus regardless of the easymagnetization direction. Which magnetic sublatticeis responsible for the magnetization anisotropy, theHo or the Co magnetic sublattice (or both) is to befound out.A polycrystalline sample of Ho2Co15Si2 wasprepared. Magnetization measurements showed thatfor this sample, the Curie temperature is near TC =830 K, and the spin-reorientation temperature isnear TSR = 295 K.We performed powder neutron diffraction in theinstrument E6. A high temperature oven and an

Orange cryostat weres used to reach temperaturesabove the Curie temperature and below roomtemperature. The neutron wavelength was 2.44 Å.Diffractograms were measured at varioustemperatures. Most of the observed reflectionscould be indexed on the basis of the Th2Zn17-typeof structure (space group R-3m). Generally,gradually increasing intensity was observed on topof the nuclear reflections when the temperature wasgradually lowered. An exception to this is foundnear the spin-reorientation temperature. Figure 1shows the diffractogram measured at 274 K,together with the difference of this diffractogramwith that measured at 302 K. The main reflectionsthat change are indexed. The decrease of the(110)/(210) reflections and the increase of the (003)reflection is in agreement with a reorientation fromeasy axis to easy plane.

Figure 1: Powder neutron diffractogram measuredat 274 K (above). Difference betweendiffractograms measured at 302 K and 274 K(below).

Preliminary Rietveld-type analysis proved difficult,because of the large number of parameters to berefined for this crystal structure. We are currentlyperforming single-crystal X-ray diffraction.Awaiting the results, we are planning to analyse theneutron diffraction data in detail in the near future.

[1] O. Tegus et al., J. Alloys Comp. 302( 2000) 21

43



Instrument E6Magnetic Structure in TmCuAlLocal Contact Karel Prokeš

Principal Proposer: P.C.M. Gubbens, TU Delft Date(s) of ExperimentExperimental Team: P. Javorský, Charles University Prague

A. Mulders, TU Delft 18.6.-21.6.2001


Neutron diffraction experiment withpolycrystalline sample was performed at = 2.44 Å.First, the diffraction patterns were measured on TmCuAlbulk polycrystalline sample at several temperaturesdown to 0.05 K. These data are used for qualitativedescription of the temperature development ofmagnetism in TmCuAl. The diffraction patterns with ahigh statistics on a powder sample of TmCuAl were thencollected at 5 K (paramagnetic state), 1.65 K and 0.4 K(two magnetic phases). At all three temperatures, wehave observed the same type of reflections as on the bulksample at the same temperature.

Refinement of the data in the paramagnetic state(5 K) gives the lattice parameters in TmCuAl a = (6.91 0.01) Å and c = (3.98 0.01) Å. The values of theatomic position parameters xTm = 0.578(2) and yAl =0.233(6) have been determined.

The temperature development, as measured onbulk material, is documented on Fig. 1. Only nuclearreflections are observed at 2.4 K. Below 2.2 K, weobserve additional purely magnetic peaks indexed by apropagation vector k = (½ 0 q) with q = 0.428. Intensitiesof the corresponding reflections increase down toT1 1.2 K and remain more-less constant below thistemperature. Further magnetic peaks described by k1 =(½ 0 ½) appear in the diffraction pattern below T1.

As concern the commensurate part, the bestagreement with our experimental data at 0.3 K we haveobtained for the spin arrangement shown in Fig. 2. Allthe Tm moments are aligned along the c-axis and have amagnitude of Tm = 2.8(1) B. Moments at (x 0 1/2 ) –we denote Tm(1) and at (-x -x 1/2 ) – Tm(3) propagatewith k1 while the moments at (0 x 1/2 ) – Tm(2)propagate with k1’ = (-½ ½ ½). Such magnetic structure

T (K)0.0 0.5 1.0 1.5 2.0 2.5

Inte

nsity

(a.u

.)

0.00

0.05

0.10

1/2 1 1/2

1/2 1 q

Fig. 1: Temperature development of the integratedintensities of two representative magnetic reflections(measured on bulk material).

+

+

+

+

+

++

+

_

_ _

_

_

_

_

_

Fig. 2: Spin arrangement in TmCuAl (commensuratepart).

was determined e.g. as the ground state in TbNiAl.For the incommensurate structure with k = (½ 0

q), the best agreement with the measured diffraction datais achieved for the Tm moments (incommensuratecomponent) along the c-axis with a sinusoidalmodulation along the c-direction (LSW). All themoments propagate with the same vector k, but momentsat Tm(2) are considerably reduced in magnitude. Themoment amplitudes are Tm = 4.7(2) B and Tm = 1.5(1)B for the Tm(1) + Tm(3) and Tm(2) positions,respectively. Moments at Tm(2) are opposite to theremaining moments. The final fit including both –commensurate and incommensurate part is shown inFig.3. The maximum moment, as derived from our data,is 7.5(2)B on Tm(1) and Tm(3) and 4.3(2)B on Tm(2).The value of 7.5B is slightly larger than the Tm3+ freeion value. A reasonable assumption leads to aconclusion, that the moment amplitude reaches the fullfree ion value. The width of the peaks corresponding to k(incommensurate) is considerably larger than for thecommensurate part (FWHM 0.45 and 0.33,respectively). It might indicate that the correlation lengthis smaller for the incommensurate component.

220 30 40 50

inte

nsity

(a.u

.)

0

2

4

110

101

200

TmCuAlT = 0.3 K

Iobs - Icalc

1/20

1/2

1/2-11/2

1/21

1/2

3/20

1/21/2-21/2

1/20q

1/20

1-q

1/2-1q 1/2

-11-q

1/21q

1/21

1-q

Fig. 3: Diffraction pattern of TmCuAl at 0.3 K; thecircles represent the experimental data, full line is the fit.

44

PHY-01-0982 // jo // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT

Magnetic structures of NdMn2-xFexGe2(x=0.3, 0.4, 1.0) as a function of temperature and pressure

Proposal N°Phy–01–982Instrument E6

Local Contact N. Stüsser**

Principal Proposer: A. Szytuła* Date(s) of ExperimentExperimental Team: A. Szytuła*, B. Penc*, N. Stüsser** 02-07.07.2001

* Institute of Physics, Jagiellonian University,Reymonta 4, 30-059 Kraków, Poland

** HMI, Glienicker Straße, 100 D-14 109 Berlin


Neutron diffraction data of NdMn2-xFexGe2 (x=0.3, 0.4and 1.0) measured in the temperature range 1.5-290 K arepresented. From these data the crystal and magneticstructure of these compounds were determine.

Magnetic data indicate: for x=0.3 the following phase transitions at 186 K (the spin

reorientation), 269 K (transition from ferro- to antiferro)and 365 K (transition from antiferro- to paramagneticstate),

for x=0.4; below 100 K a ferromagnetic order. Withincrease of the temperature the magnetic phase at about150 K has an antiferromagnetic character and next(between 200 K and 235 K) ferromagnetic,

for x=1.0 the antiferromagnetic order is state up to 194K [1].

Analysis of the nuclear peak intensities indicate thatthese compounds exhibit the tetragonal ThCr2Si2-typecrystal structure (I4/mmm space group). In this structureNd atoms occupy 2(a) positions Mn and Fe atoms arestatistically occupies 4(d) positions and Si atoms occupy4(e) position.

Analysis of the magnetic peak intensities give thefollowing models of the magnetic structure.

For x=0.3 in the temperature range 1.5 K-200 K the Mnmagnetic moments form a noncollinear ferromagnetic orderFmc-type [2]. Mn moment form angle ? with the c-axisequal 430(30) at 1.5 K and 30 K and 600(80) at 150 K and200 K. At275 K the Mn moments form collinear antiferromagneticorder AFl-type with the moment parallel to the a-axis.

For x=0.4 the Mn moments at T=1.5 K and40 K form a noncollinear ferromagnetic order Fmc-type.With increasing temperature in100 K<T<210 K range the noncollinear antiferromagneticordering of AFmc-type is stable, while at 260 K the simpleantiferromagnetic ordering AFl-type with the Mn momentparallel to the a-axis.

For x=1.0 in the temperature range 1.5 K -203 K theMn magnetic momentd form a simple collinearantiferromagnetic structure AFil-type with the Mnmagnetic moment parallel to the c-axis.

Fig. 1 shows the thermal variation of the Mn moments.The obtained data indicate the small change of the value ofthe Mn magnetic moment with the concentration.

Fig. 2 shows the thermal variation of the latticeparameters a and c for the investigated compounds. ForNdMn1.6Fe0.4Ge2 compound is observed the anomaly in thethermal dependence of a- and c- lattice parameters at the F-

AF transition. Above results indicate the connectionbetween the magnetic order and Mn-Mn interatomicdistances. Because the external pressure influences theinteratomic distances it is interesting to perform themeasurements of the neutron diffraction under the externalpressure, which are planned in the next proposal.References[1] G. Venturini et al., J. Alloys Compd. 237 (1996) 61.[2] G. Venturini et al., J. Magn. Magn. Mater. 150

(1995) 197.

0 50 100 150 200 250 3001.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0Fig. 1

NdMn1.7Fe0.3Ge2 NdMn1.6Fe0.4Ge2 NdMnFeGe2

Mag

netic

mom

ent p

er M

n io

n [

B]

Temperature [K]

0 50 100 150 200 250 300

4.014.024.03

4.05

4.06

4.07

4.08

0 50 100 150 200 250 30010.70

10.72

10.74

10.82

10.84

10.86

Fig. 2

NdMn1.7Fe0.3Ge2 NdMn1.6Fe0.4Ge2 NdMnFeGe2

a [A

]

Temperature [K]

c [A

]

45


EXPERIMENTAL REPORT Proposal N°Phy–01–983Instrument E6Magnetic structures and phase transitions in RRhSi

(R=Tb-Er) compounds. Local Contact N. Stüsser**

Principal Proposer: A. Szytuła* Date(s) of ExperimentExperimental Team: A. Szytuła*, Ł. Gondek*, B. Penc*, N. Stüsser**


** HMI, Glienicker Straße, 100 D-14 109 Berlin02-08.04.2001,


Neutron diffraction and magneticmeasurements show that RRhSi (R=Tb-Er) areantiferromagnets below the Nèel temperatureequal to 26 K for R=Tb, 14.6 K for R=Dy, 8.5K for R=Ho and 8.5 K for R=Er. All thesecompounds crystalize in the orthorombicTiNiSi – type structure (P nma). The 4(c) sites:

zxzxzxzx 21

41

21

21

43

21

43

41 ,,;,,;,,;,,

are occupied by 4 rare earths atom, 4 Rh atomsand 4 Si atoms with different values of x and zparameters.

The new diffraction maesurements givethe following magnetic structures:

At 1.5 K the magnetic structure of TbRhSi isdescribed as a sine-wave modulated one withthe propagation vector ))2(204.0),2(393.0,0(k

.Tb magnetic moments equal to 7.87(17) µBform the angles: θ=34(3)o with the c-axis andφ=18(4)o with the a-axis. Near by 16 K ittranstorms into a magnetic structure representedby the propagation vector )0),3(3878.0,0(k

.The Tb magnetic moments equal to 5.3(1) µBare parallel to the b-axis. This type of themagnetic ordering is stable up to the Nèeltemperature (26 K).

The magnetic peaks in the neutron diffractionpattern of DyRhSi collected at 1.5 K could beindexed with the propagation vector

),0,( 21

21

k

. The best agreement with theexperimental data is obtained for the collinearmagnetic structure with Dy magnetic momentsequal to 8.1(4) µB and are parallel to the b-axis.Temperature dependence of the magneticsusceptibility gives the Nèel temperature equalto 14.6 K and an additional transition at Tt=5.4K. The peaks of the magnetic origin in in the7.5 K pattern could be quite well indexed bythe wave vector ))2(515.0,0),2(418.0(k

. TheDy magnetic moments, equal tp 6.8(4) µB form

a sine-wave modulated structure, and areparallel to the b-axis.

The magnetic reflections in the HoRhSi neutrondiffraction pattern obtained at 1.5 K areindexed by the propagation vector ),0,( 2

12

1k

.The Ho magnetic moments at 1.5 K amount9.03(18) µB, and are parallel to the b-axis. Themagnetic order is stable up to the Nèel point at8.5 K.

For ErRhSi a commensurate magnetic structuredescribed by the propagation vector )0,,0( 2

1k

coexists with the incomensurate one withvector )0),4(418.0,0(k

. In the comensuratephase the Er moment equals to 5.50(15) µB,while in the incomensurate phase this momentamounts 4.75(12) µB. In both phases the Ermoments are parallel to the a-axis. Withincrease of the temperature the commensuratephase disappear at 2.3 K. The magnetic peaksat 4 K are indexed with the propagation vector

)0),2(4173.0,0(k

. This order is stable up to theNèel temperature equal to 8.5 K.

HoRhSi neutron diffraction pattern at 1.5 K, theinset shows intensity of the 000± magnetic peak.

10 20 30 40 50 60 70 80 90

1 2 3 4 5 6 7 8 9

0

200

400

600

800

1000

1200

1400

1600

Inte

nsity

[a.u

.]

Temperature [K]

Cou

nts

[a.u

]

2 [deg.]

Iexp Icalc Iexp - Icalc Bragg positions

46

PHY-01-0984 /// 22.03.02 Seite n 1

EXPERIMENTAL REPORT Proposal N° PHY-01-984Instrument E6Onset of Ferromagnetic-like Behaviour in

Nanostructured ZnFe2O4 – High TemperatureMagnetic Transitions Local Contact

N. Stüßer

Principal Proposer: S.J. Campbell, UNSW@ADFA, AustraliaM. Hofmann, ISIS Date(s) of Experiment

Experimental Team: M. Hofmann, S.J. Campbell 11.5. – 15.5.2001


The normal spinel ferrite ZnFe2O4 ordersantiferromagnetically below 10.5 K whereasnanostructured ZnFe2O4 prepared bymechanochemical means indicates ferromagnetic-like behaviour to ~ 500 K [1]. In our relatedinvestigation of milled ZnFe2O4 by X-raydiffraction and Mössbauer spectroscopy we haveestablished that the mean degree of inversionincreases to i ~ 0.75 as the mean particle sizesdecrease towards <d> ~ 8 nm, reflecting thesystematic evolution towards an inverse spinelstructure on milling [2]. Our recent neutron powderdiffraction measurements (1.5-300 K) on a set ofsix ZnFe2O4 samples milled with a low energy ballmill (LEM 0-120 h) have provided detailed insightto the weakening of the antiferromagnetic couplingwith increasing milling time [3]. In the presentwork we have investigated the same samples tohigh temperature (300-600 K) as well as 3 samplesmilled in a high energy ball mill (SPEX 2-12 h; 2-600 K) in order to determine the magnetictransition temperatures and to clarify thisunexpected occurrence of ferrimagnetic/ferromagnetic-like behaviour in nanostructuredZnFe2O4. An overall aim is to clarify the linkbetween the particle size (fig 1) and degree ofstructural inversion and the magnetic order.

0 2 4 6 8 10 120

5

10

15

20

25

30

350 20 40 60 80 100 120

SPEX

d [n

m]

tm [h]

tm [h]

Figure 1. Particle sizes of milled ZnFe2O4 [2].

Low temperature neutron powder diffractionmeasurements on the series of mechanochemicallytreated samples of ZnFe2O4 (LEM 0-120 h; SPEX2-12 h) reveal that the fraction of theantiferromagnetically ordered phase decreases withdecreasing particle sizes (fig 2). Below ~ 20 nmonly short range antiferromagnetic ordering isfound, which in turn vanishes below <d> ~ 10 nm.

0 20 40 60 80 100

SPEX 12 h

SPEX 4 h

SPEX 2 h

120 h

100 h

60 h

40 h

20 h

co

unts

2 angle

Figure 2. Neutron diffraction patterns of milledZnFe2O4 samples at 2 K.

The high temperature neutron diffractionmeasurements reveal ferromagnetic-like order onlyin ZnFe2O4 milled with the high energy mill (SPEX4-12 h) with no evidence of short range AF order inthese samples. The ordering temperature for thesenanostructured ZnFe2O4 samples was found to be ~470 K. The systematic increase in the inversionparameter with decreasing particle size observed inthe present neutron and X-ray diffraction results(fig 1) and earlier studies, reflects a gradualtransformation from the normal spinel of thestarting material, to an increased fraction of Fe3+

ions on the tetrahedral sites.

[1] W Schäfer, W Kockelmann, A Kirfel, W Potzel, F JBurghart, G M Kalvius, A Martin, W A Kaczmarek and S JCampbell, Mater Sci Forum 321-324 (2000) 802-807[2] H Erhardt, S J Campbell and M Hofmann, J Alloys andCompounds (in press, 2002)[3] M Hofmann and S J Campbell, BENSC 2000 AnnualReport (PHY-01-853)

47


EXPERIMENTAL REPORT ProposalN°PHY-01-1032Instrument E6Search for diffuse intensity in the reciprocal

space of the heavy-fermion compound Ce2RhIn8 Local Contact: N. Stüßer*

Principal Proposer: E. G. Moshopoulou (NCSR Demokritos) Date(s) of ExperimentExperimental Team: E. G. Moshopoulou (NCSR Demokritos),

N. Stüßer (HMI), J. Hernandez-Velasco (HMI)E. Garcia-Matres (Univ. Augsburg) *6 November 2001

Date of Report: 11 *February 2002

CemTnIn3m+2n (T = Co, Rh, Ir; m = 1, 2; n= 1) is the first linear homologous series ofheavy electron compounds. The members ofthe series exhibit fascinating and sometimesunusual (for a heavy fermion) properties.

We focus here on the m = 2, n = 1member, Ce2RhIn8. This compound is a heavy-fermion antiferromagnet with TN = 2.8 K andSommerfeld specific heat coefficient ~ 400mJ/mol Ce K2 above TN. Conventional powderx-ray diffraction showed that the materialadopts tetragonal structure with space groupP4/mmm and a = b = 4.665(1) Å, and c =12.244(5) Å. However, the selected areaelectron diffraction patterns of Ce2RhIn8 exhibitan additional feature, which makes thismaterial both fascinating and complex. Theydisplay diffuse streaks running along the [001]*direction. Understanding the static or dynamicdisorder associated with this diffuse scatteringshould lead us to establish an accuratestructure-property relationship and gain insightinto the intriguing physical properties of thematerial.

The aim of our single-crystal diffractionexperiment on E6 was to test whether thediffuse intensity, found by electron diffraction,could be observed and measuredquantitatively by neutron diffraction. As firststep, a crystal of Ce2RhIn8 was oriented in thediffractometer and several Bragg reflectionswere measured. However, no diffusescattering could be observed among the Braggpeaks even for long counting time.

48

PHY-01-1045 // brandt // 22.03.02


Instrument E6Temperature dependence of theantiferromagnetic order parameter of FeWO4

Local Contact Dr. N. Stüßer

Principal Proposer: U. Köbler, FZ-Jülich, IFF Date(s) of ExperimentExperimental Team: A. Hoser, Inst. f. Kristallogr., RWTH Aachen

02.-07.08.2001


Systematic investigations of many magneticmaterials with a pure spin moment (quenchedorbital moment) revealed that the thermaldeviation of the magnetic order parameter fromits saturation value at absolute zero canaccurately be described by a single T powerterm up to a temperature of 0.7Tcrit. Incontrast to the classical spin wave theory theempirical exponent is independent of the spinorder type but it depends on whether the spinquantum number is integral or half-integral and–of course- on the dimension D of the magneticinteractions which can be D = 3, 2, or 1. Thesix-fold scheme of exponents defined in thisway is given in Table I together with onetypical material [1]. It should be noted that forbulk material with anisotropic interactions thesame exponent as for materials with two-dimensional interactions applies.In order to further test the universality of TableI we have performed neutron diffractionexperiments on commercially availableFeWO4 powder material. The spin of the Fe2+

ion is S=2 in FeWO4. Since the latticesymmetry is monoclinic (space group P2/c) themagnetic interactions can, but need not, beanisotropic. For isotropic interactions oneexpects =9/2 but for anisotropic interactionsone expects =2 according to Table I. Theexperimental sublattice magnetization data (seefig.1) follow a T9/2 dependence over a largetemperature range but for T35 K smallsystematic deviations from this dependence canbe noticed. This can be viewed as a badlyresolved crossover to a T2 dependence as istypical for a change from isotropic toanisotropic interactions. For NiO a similarcrossover phenomenon occurs but much betterresolved [1].

[1] U.Köbler, A.Hoser, J.Englich, A.Snezhko,M.Kawakami, M.Beyss and K.Fischer: J. Phys.Soc. Japan 70 (2001) 3089.

integral spin half-integral spinS = 1 S = 2 S = 1

2 S = 32 S = 5

2 S = 72

UO2 FeBr2 KCuF3 CrBr3 CsFeF4 EuO

T2T92

T2 T32

CrO2 Mn2O3 K2CuF4 CrCl3Gdmetal

3D-a

niso

tropi

c3D

isot

ropi

c1D

(axi

al) MnF2FeF2

2 D

T 3T T52

Table 1.

.

0 500 1000 1500 2000 2500 3000 350042

43

44

45

46

47

48

49

50

FeWO 4

(Inte

nsity

) 0.5

( a. u

. )

T 2 ( K ) 2

T =76 K N

T9_2

49

Fig 1

Seite 1 von 1


EXPERIMENTAL REPORT Proposal N° PHY-01-1048Instrument E6Magnetic Instability in Er0.7Y0.3Co3

Local ContactN.Stüßer

Principal Proposer: Ernst Gratz, Inst.f. Exp.physik, TU-Wien Date(s) of ExperimentExperimental Team: Ernst Gratz, Inst.f. Exp.physik, TU-Wien

A. Hoser, RWTH-AachenN. Stüßer HMI

24.07.-01.08.2001


In our recent Report (Nr.:978) we reportedabout an investigation of an instability in theCo sublattice of ErCo3. This ferrimagneticcompound (TC=402K) crystallizes in the rhom-bohedral PuNi3 – type structure, with two Er -sites and three Co – sites. The most significantresult of this investigation is that when lower-ing the temperature, the Co – moments on twoof the three Co - sites crossover (in a first ordertransition) from a weak ferromagnetic state intoa strong ferromagnetic state at 100K (i.e. theCo moments change their values discontinu-ously at 100K) [1] . To study this metamagnetic instablility in theCo-sublattice we reduced the molecular field inErCo3 by replacing Er by Y in the pseudobi-nary (Er0.7Y0.3)Co3 – compound (TC=380K).The aim of the neutron studies was also to findout the reason for a strong peak, observed inthe specific heat at 35K. Neutron pattern havebeen measured between 2K and 400K. Therefinement of the patterns below the orderingtemperature, down to 40K, revealed a collinearferrimagnetic structure. At 35K and for lowertemperatures the increasing intensity of the(003) reflection in the neutron patterns indi-cates a contribution of a magnetic momentcomponent perpendicular to the c-axis. Thatmeans, that at least some of the magnetic mo-ments are no longer aligned along the c-direction. (Fig. 1. shows the temperature de-pendence of the (003) reflection). However,there is also a discontinuous increase of theintensity of the magnetic reflection at 35K,which might be considered as the metamagen-tic transition which we are looking for.It appeared however that the refinement of thepatterns below 35K is extremely difficult, sincethere are five different magnetic moments andeach of them can in principle change its direc-tion and its magnitude. The refinement of theneutron pattern at 40K gives the following val-

ues: ErI: m=6.899B; ErII: m=6.733B; CoI:m= -1.157B; CoII: m= -1.561B; CoIII:m= -0.711B. In order to overcome the prob-lems with the refinement and to clarify themechanism behind the spin-reorientation at35K (accompanying the metamagnetic transi-tion) in the Co sublattice, we asked for beam-time to study two further compounds((Er0.9Y0.1)Co3, (Er0.5Y0.5)Co3).

Reference1. E.Gratz, A.S. Markosyan, V.Paul-Boncour.A.Hoser, N.Stuesser, I.Gaidukova, V. Rodmin,J. Applied Phys. (in press)

15 16 17 18 19 200

500

1000

1500

2000

2500

3000

3500

4000

2K,11K,20K

35K

40K

(0 0 3)

Inte

nsity

0 10 20 30 400

1000

2000

Inte

nsity

Temp [K]

Fig. 1.: Temperature dependence of the (003) reflectionin (Er0.7Y0.3)Co3. Inset: Intensity of the (003) re-flection vs. temperature.

50


EXPERIMENTAL REPORT Proposal N° PHY-01-1049Instrument E6Magnetic structures and magnetic phase

transitions in Tb6Co2Sn Local Contact K. Prokes,M. Hofmann

Principal Proposer: Oleksandr Kolomiyets, Charles Univ. Prague Date(s) of ExperimentExperimental Team: Svoboda Pavel, Charles Univ. Prague

Javorsky Pavel, Charles Univ. PragueSechovsky Vladimir, Charles Univ. Prague

27.09-31.09.2001


The main goal of the experiment was todetermine magnetic phase transitiontemperatures and the corresponding magneticstructures of Tb6Co2Sn.

In order to achieve this goal neutronpowder diffraction patterns were collected atvarious temperatures ranging from 1.5 K to300 K provided by orange cryostat (Fig. 1).Special attention was devoted to the vicinity ofthe temperatures, at which magnetization

curves show anomalies, that is 36 K and 42 K.The diffraction data obtained at room

temperature indicate that the main phase inthe studied sample is indeed Tb6Co2Sn,although there is also minor admixture ofTbCo2 and Tb5Sn3. The detailed temperaturescan of the low-angle part of the patternrevealed that magnetic intensity starts to buildup already between 50 K and 60 K (seeFig. 2). As the temperature is decreased below50 K no additional diffraction peaks appear(Fig. 2) only the intensity of the existing ones isgrowing (note the similarity between Fig.1 and3), indicating no further change of themagnetic structure.

So the neutron diffraction experimentbrings two important additions to theinformation obtained from bulk magnetizationstudies: (1) the real ordering temperatureshould be around T = 55 K, (2) no modificationof magnetic structure occurs below T = 50 K.

Currently the data are being refined inorder to determine the exact magneticstructure of the material.

20 40 600

5000

10000

15000

20000

Intensity

(cou

nts)

2 (°)10 20 30 40 50 60

0

5000

10000

15000

20000

Fig. 1. Diffraction patterns obtained at T = 1.5 K (emptycurve) and 120 K (filled curve). The difference is due to

magnetic intensity.

8 10 12 14 16 18 20 22 24 26

50010001500200025003000

515

253335

3739

4143

4550

6070

80120

Tb6Co2.35Sn0.65temperature scan

T (K)

2

Intensity

Fig. 2. Temperature dependence of the low-angle part ofthe neutron diffraction pattern

10 20 30 40 50 60

0

2000

4000Tb6Co2.35Sn0.65difference between1.5 K and 39 K patterns

Intensity

(cou

nts)

2

Fig. 3. Differential curve for the patterns collected atT = 1.5 K and 39 K.

51

EXPERIMENTAL REPORT

Magnetic Structure and Domain Formation in

ErAuGe


Instrument E6

Local Contact

N. Stüsser


29. 10. - 31. 10. 2001

Principal Proposer: S. Baran, Jagellonian University, Kraków, Poland

Experimental Team: N. Stüsser, J. Hernandez-Velasco, HMI, Germany

A. Szytuªa, B. Penc, Jagellonian University, Poland

J. Leciejewicz, INCT, Warszawa, Poland


Introduction

An anisotropic magnetic peak broadening was re-

ported to exist in neutron diraction patterns of

ErAuGe while no broadening was found in case

of HoAuGe [1, 2] (compare also our experimental

reports on: PHY-01-754, PHY-01-851, PHY-01-

917). The origin of the observed broadening is

not clear. The following are the propositions of

possible explanation:

magnetic disorder on Er atomic sites [1]

limited magnetic domain size in the direc-

tion parallel to the direction of propagation

vector [2]

The main subject of reported research were the

systematic studies of magnetic peak broadening

in solid solutions ErxHo1xAuGe (x = 0:25, 0.5,

0.75).


The samples were obtained by arc melting in ar-

gon atmosphere with the use of the respective el-

ements (minimum purity 3N), and were annealed

at 800 oC for one week.

Neutron diraction patterns were recorded on

the diractometer E6 at the Berlin Neutron Scat-

tering Center. The incident neutron wavelength

was 2.44Å. The data were collected between

1.5 K and 8 K. The neutron diraction data were

analyzed with the use of the Rietveld program

FULLPROF [3].

The neutron diraction patterns of investi-

gated compounds, collected at temperature T =

8 K (i.e. above the Néel temperature), con-

rmed that samples crystallized in the hexagonal

LiGeGa-type structure the same type of struc-

ture as was found in case of RAuGe (R = Ho,

Er).

The positions of magnetic peaks found in the

neutron diraction patterns collected at T =

1:5 K were identical with those found in the neu-

tron diraction patterns of RAuGe (R = Ho, Er)

collected at the same temperature. This fact in-

dicates the existence of the same magnetic order-

ing within the entire family of compounds. How-

ever, a magnetic peak broadening was found in

case of Er0:5Ho0:5AuGe while no such broadening

was found for ErxHo1xAuGe, where x = 0:25,

0.75.

The results presented above allow for the con-

clusion that the magnetic peak broadening does

not depend only on a sample composition (al-

though it is worthwhile to note that it was ob-

served only for samples containing Er) but de-

pends also on some other factors. Probably, the

most important among these factors are the con-

ditions in which the samples were prepared.

References

[1] B. J. Gibson, Investigation of the Physical

Properties of the Ternary Intermetallic Rare-

Earth Compounds, RETGe (RE = Sc, Y, La-

Lu; T = Ag, Au), Doctoral Thesis, Loughbor-

ough University, December 1998

[2] S. Baran, M. Hofmann, G. Lampert,

N. Stüsser, A. Szytuªa, D. Többens,

P. Smeibidl, S. Kausche, J. Magn. Magn.

Materials 236 (2001) 293

[3] J. Rodriguez-Carvajal, Physica B 192 (1993)

55

52


EXPERIMENTAL REPORT Proposal N° PHY-01-1055Instrument E6Neutron diffraction studies of RNiSn2 (R=Tb-Er)

compounds Local Contact DR. N. Stüsser

Principal Proposer: A. Szytuła1 Date(s) of ExperimentExperimental Team: A. Szytuła1, B. Penc1, S. Baran1, J. Leciejewicz2

N. Stüsser31Institute of Physics Jagiellonian University, Cracow, Poland2Inst. of Nuclear Chemistry and technology, Warsaw, Poland3BENSC. Hahn-Meitner Institute, Berlin, Germany

26 – 30. 11. 2001

Date of Report: 14. 01. 2002Introduction and experimental remarksIn this work we report the results of neutrondiffraction measurements performed for ternary in-termetallic RNiSn2 compounds (R=Tb, Dy, Ho).The polycrystalline samples were obtained by mel-ting the constituent elements in pure argon atmo-sphere. After melting the samples were annealed at773 K for several days. The measurements werecarried out in BENSC (neutron wavelength 2.44 Å).The Rietvield type program FullProf was appliedfor data handling the diffraction spectra.Crystal structureThe neutron diffraction patterns recorded in para-magnetic state confirm that all of the compoundscrystallize in the orthorhombic LuNiSn2 structurewith Pnma space group. The 4(c) sites ;,¼,( zx

;,¾, zx ;½,¾,-½ zx )-½,¼,½ zxare occupied by 12R (in three sublattices), 12 Ni (inthree sublattices) and 24 Sn (in six sublattices)atoms with different x and z parameters. Magnetic structuresTemperature dependence of the magnetic suscepti-bility indicate that all compounds are antiferro-magnets with the Néel temperature 5.2 K for R =Tb, 6.5 K for R = Dy and 2.2 K for R = Ho.In the mentioned compounds the R3+ ions aredistributed over 3 different sublattices. The mag-netic reflections observed in the neutron diffractionpatterns of the RNiSn2 compounds can be indexedin the same magnetic unit cell as the crystallo-graphic one. The analysis of the Bertaut theory [1](based on irreducible representations for spin trans-formation of the 4(c) site in the space group Pnma)leads to the one ferro- and three antiferromagneticstructures described by following vectors:F=S1+S2+S3+S4; G=S1-S2+S3-S4; C=S1+S2-S3-S4;A=S1-S2-S3+S4. The magnetic structures of RNiSn2compounds at 1.5 K are described in Table 1. This type of magnetic order is stable up to the Néeltemperature.The neutron diffraction data show that in thedescribed RNiSn2 compounds magnetic momentsare localized only on the rare earth atoms. Nomagnetic moment was detected on Ni atoms withinthe accuracy of the experiment.

The direct interactions between electron shells ofR3+ ions are highly improbable because thedistances between R3+ ions in RNiSn2 compoundsare long. Two factors influence the stability of theobserved magnetic structures in our compounds:interaction via conduction electrons (probablyRKKY model) and crystalline electric field (CEF).Table 1 Magnetic structures of RNiSn2 compoundsCompound sublattice R1 R2 R3

structure AyFz CxFz Fz

x(B) 0 2.3(3) 0y(B) 0.7(3) 0 0z(B) -2.6(3) -4.9(3) 5.0(4)

TbNiSn2

total(B) 2.74(37) 5.5(3) 5.0(4)structure AyFz CxFz Fz

x(B) 0 3.27(37) 0y(B) 1.9(5) 0 0z(B) -5.1(3) -7.3(3) 6.8(4)

DyNiSn2

total(B) 5.4(4) 8.03(34) 6.8(4)structure Az Az AzHoNiSn2

z(B) 5.86(14) 5.31(15) -5.87(16)

T=1.5 KTbNiSn2

Num

ber o

f cou

nts

[a. u

.]

2 [o]

Iobs Ical Iobs-Ical

Bragg positions

10 20 30 40 50 60 70

T=10 K

Observed and calculated neutron powder diffractionpatterns of TbNiSn2 at the T = 1.5 and 10 K.[1] E. F. Bertaut, Acta Crystallogr. A 24 (1968) 217

53


EXPERIMENTAL REPORT Proposal N° PHY-01-1056Instrument E6Neutron diffraction studies of RRhGa (R=Tb – Er)

compoundsLocal Contact J. Hernandez Velasco

Principal Proposer: A. Szytuła1 Date(s) of ExperimentExperimental Team: A. Szytuła1, B. Penc1, J. Hernandez Velasco2

1Institute of physics, Jagiellonian University, Cracow, Poland2BENSC, Hahn-Meitner Institute, Berlin, Germany

29. 10 – 5. 11. 2001

Date of Report: 14. 01. 2002Introduction and experimental remarksIn this work we report the results of neutrondiffraction measurements performed for ternary in-termetallic RRhGa compounds (R=Tb, Ho, Er).The polycrystalline samples were obtained bymelting the constituent elements in pure argonatmosphere in arc furnace. After melting thesamples were annealed at 1073 K for 1 week. Themeasurements were carried out in BENSC (neutronwavelength 2.44 Å). The Rietvield type programFullProf was applied for data handling thediffraction spectra.Crystal structureThe neutron diffraction patterns recorded in para-magnetic state confirm that all of the compoundscrystallize in the orthorhombic TiNiSi structurewith Pnma space group. The 4(c) sites ;,¼,( zx

;,¾, zx ;½,¾,-½ zx )-½,¼,½ zxare occupied by 4R, 4Rh and 4Ga atoms withdifferent x and z parameters. Magnetic structureTemperature dependence of the magnetic suscepti-bility suggests the antiferromagnetic orderingbelow 22 K for TbRhGa, 5.2 K for HoRhGa and5.6 K for ErRhGaDiffraction peaks of magnetic origin were observedin all patterns collected at temperatures below theNéel temperatures for all RRhGa compounds. Allof the peaks can be indexed with the propagationvector k=(0, ½, 0). The best agreement with theexperimental data for TbRhGa was obtained for thecollinear antiferromagnetic structure described byvector G = S1 - S2 + S3 - S4 with the Tb magneticmoment equal to 8.15(11)µB and parallel to the a-axis. The Néel temperature of TbRhGa amounts 21K. The magnetic structures of HoRhGa andErRhGa are similar as TbRhGa. The differencesbetween intensities of magnetic peaks of ourcompounds suggest the other orientation of themagnetic moments in the HoRhGa and ErRhGacompounds. The best fit was obtained for followingstructure parameters:- the Ho magnetic moment amounts 7.67(11) µB,

lies in a-b plane and forms angle =35(3)o

with a-axis (Rmag=5.26%).

- the Er magnetic moment amounts 7.16(13) µB,and forms angle =38(3)o with c-axis and=27(9)o with a-axis (Rmag=12%).

The Néel temperatures are 4.6 K and 4.0 K forHoRhGa and ErRhGa respectively. The magnetic structures described by wave vectork=(0, ½, 0) are stable in the temperatures between1.5 K and TN in all described in this reportcompounds. The long distances between R3+ ions inRRhGa compounds suggest the high improbabilityof direct interactions between electron shells of R3+

ions. Two factors influence the stability of theobserved magnetic structures in our compounds:interaction via conduction electrons (probablyRKKY model) and crystalline electric field (CEF).

Observed and calculated neutron powder diffractionpatterns of HoRhGa at the T = 1.5 and 10 K.

T = 1.5 K

HoRhGa

I [a.

u.]

T [K]

2 [o]

Yobs. Ycal. Yobs.-Ycal. Bragg positions

Num

ber o

f cou

nts

20 30 40 50 60 70

11302

030

101

321

2

103

211

202

112

210

201

111

200

1

02

011

002

101

022

211

112

012

111

110

011

101

T = 10 K

1 2 3 4 5

020406080

100120140160

010 011 110 111

54


EXPERIMENTAL REPORT Proposal N°Phy–01–1057Instrument E6Neutron diffraction study Ce2Co1-xAuxSi3 (x=0.4, 0.6,

0.8, 1.0) Local ContactJ.H. Velasco**

Principal Proposer: A. Szytuła* Date(s) of ExperimentExperimental Team: A. Szytuła*, B. Penc*, J. H. Velasco**


** HMI, Glienicker Straße, 100 D-14 109 Berlin29.10-05.11.2001


Polycrystalline samples of Ce2Co1-xAuxSi3for x equal to 0.4, 0.6, 0.8 and 1.0 have beenstudied by neutron diffraction. All compoundsexhibit the hexagonal crystal structure derivedfrom the AlB2-type. For x=0.4 the Ce magneticmoments equal to 0.6(1) µB form a simpleantiferromagnetic structure and are parallel to the b-axis. In Ce2Co0.2Au0.8Si3 a short range magneticorder is observed. For x=0.6 and 1.0 the Ce-moments do not order up to 1.5 K.

The neutron diffraction experimentconfirms that the Ce2Co1-xAuxSi3 (x=0.4, 0.6, 0.8and 1.0) compounds have the hexagonal structureof Ce2CoSi3 type. The data for Ce2AuSi3 suggestthat the stechiometric sample with this compositiondoes not exist. The neutron diffraction data givedifferent magnetic properties at low temperatures(1.5 K). In the case of the compound with x=0.4 theneutron diffraction data confirm the existence atlow temperatures of a long-range magnetic order ofcerium moments. The determined magneticstructure is similar to that observed in theisostructural Ce2RhSi3. The determined Cemagnetic moment equal to 0.6(1) µB is smaller thatthat observed in Ce2RhSi3 (1.3(1) µB). In both thesecompounds the Ce magnetic moments in an orderedstate are reduced, as compared to the value for thefree Ce3+ ion value (gJ=2.14 µB). The sametendency has been observed in a large number ofcerium intermetallic compounds and is commonlyattributed either to valence fluctuations or to theKondo effect. For Ce2Co0.2Au0.8Si3 the short-rangeantiferromagnetic correlations similary to thoseobserved in Ce2PdSi3 are observed. InCe2Co0.4Au0.6Si3 and Ce2AuSi3 the magnetic orderis not detected up to 1.5 K. It is in contradictionwith the macroscopic data (temperature dependenceof the specific heat and magnetic susceptibility)which indicate an existence of the magnetic orderin these compounds at low temperatures.

The obtained results are in good agreementwith the results of the magnetization measurements.The magnetization curve for x=0.4 at T=2 K has ametamagnetic transition with Hcr 10 kOe typical for

an antiferromagnet while for x=0.8 and 0.9 the Hcris near 1 kOe. Neutron diffraction data give newresults concerning the stability of the magneticordering in these compounds.

Fig. 1 Observed and calculated neutrondiffraction patterns of Ce2Co0.6Au0.4Si3 at a) 10Kand b) 1.5K. The inset shows the temperaturedependence of the 010 and 011 magnetic peaksintensity.

For details see:Ł.Gondek, S.Majumdar, E.V.Sampathkumaran,B.Penc, N.Stüsser and A.Szytuła, Acta PhysicaPolonica B vol. 32 (2001) No 10, p. 3393-3398 andJ.Magn.Magn. Mater. (in press)

55


EXPERIMENTAL REPORT Proposal N° phy 01 1058Instrument V10, E6Field dependence of the magnetic structure in

cubic rare earth dodecaboridesLocal Contact Siemensmeyer K.

Principal Proposer: Flachbart K., IEP Kosice, Siemensmeyer K., HMI Date(s) of ExperimentExperimental Team: Matas S., Günther D. Siemensmeyer K.,

Meissner M., HMI BerlinFlachbart K., IEP Kosice

April, 1th – 10th October2001

Date of Report: Dec. 4, 2001

We have investigated the magnetic orderingof HoB12 using isotopically enriched powder forneutron diffraction and small single crystalsprepared from natural elements for specific heatmeasurements. The specific heat data confirm thephase diagram found previously: The phasetransition to the magnetically ordered state is offirst order, followed by a second, field inducedsecond order transition which is absent in fieldsabove 2 T. The effective ground state is J=1, inagreement with earlier data of N. Shitsevalova [1].The entropy change connected with the fieldinduced transition was too small to be detected, italso indicates that this transition is continuous.

Neutron diffraction in zero field reveals anantiferromagnetic structure with commensuratepropagation vectors (0 2/3 2/3) and (2/3 1/3 2/3).The observed reflections probably can be explainedby a multiple q structure, the experiment suggeststhat the dimensionality of the order parameter isn=6 and d=3. A distortion of the fcc – symmetrycould not be observed, therefore we believe that theuniversality class has been determined with theexperiments.

In applied field, the principal reflectionsremain, i.e. no change occurs in theantiferromagnetic propagation vectors. In contrast,the intensity of the observed reflections changesdramatically. This can be associated with areduction of the antiferromagnetic moment whichat maximum reaches 50%, in parallel theferromagnetic moment in field direction increases.The neutron data are in good agreement with thecontinuous nature of field induced transition. It is,however, more difficult to make conclusions to itsmicroscopic nature: As the 4f moment is notexpected to change its magnitude, some decouplingprocess of multi - q ordering vectors could beimagined. In applied field the magnetic backgrounddecreases compared to the zero field reference. Thiscan only be interpreted under the assumption thateven at the lowest temperatures, some disorderremains in zero field which is removed only by theexternal field.

A study on a single crystal is planned incontinuation of this work to investigate the field

induced phase transition further. Another point offundamental interest is the study of the criticalbehaviour of this system close to TN to testpredictions of the renormalisation group theory forn=6, d=3 [2]. These points could not beinvestigated with the powder samples used forneutron study here [3].

[1] N. Shitsevalova, Thesis, Univ. Wroclaw,Poland, 2001. [2] P. Bak and D. Mukamel, Phys. Rev. B 13(1976) 5086.[3] S. Matas et al., Proc. of ICNS, München 2001.

0 2 4 6 8 10 12 140

3

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9

B=0 0.1T 0.2T 0.3T 0.4T 0.5T 0.6T 0.7T 0.8T 0.9T 1.0T 2.0Tc(

J/m

olK)

Temperature (K)

Fig. 1: Specific heat of HoB12 in various magneticfields.

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-500

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Diffence plot high temperature scan (15K) low temperature scan (1.7K)

CTS

H2+K2+L2 (R.L.U.)2

Fig. 2: Difference between powder scans at low(1.7 K) and high (15 K) temperature at B = 0.

56


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x inYbMn2Si2-xGex


Instrument E6Valence and Magnetic Transitions inYbMn2Si2-xGex Local Contact

N. Stüßer

Principal Proposer: M Hofmann, ISIS, S J Campbell, UNSW@ADFA Date(s) of Experiment

Experimental Team: M. Hofmann, ISISN. Stüßer, HMI 15.10-21.10.2001


Rare-earth intermetallic compounds containingytterbium exhibit a wide range of interesting andunusual physical and magnetic properties (e.g. [1]).This occurs mainly as a result of their mixedvalence states (II/III) or changes from one valencestate to the other.

Nowik et al. [2] have recently investigated themagnetic phase transitions in the YbMn2Si2-xGexseries (crystallising in the tetragonal ThCr2Si2 typestructure) by magnetisation and Mössbauer effectstudies on 57Fe doped samples. A number oftransitions were observed in the limiting YbMn2Ge2and YbMn2Si2 compounds, deemed to be divalentand trivalent respectively. Several aspects of themagnetic behaviour of YbMn2Ge2 and YbMn2Si2remained unknown and we carried out a neutrondiffraction investigation to determine theirmagnetic structures [3, 4]. In this study we havenow investigated a series of additional YbMn2Si2-

xGex samples (x = 0.4, 1.0, 1.4, 1.6 and 1.8) in thetemperature range 1.5 – 300 K to clarify the linkbetween the magnetic behaviour and valence statein this system. Together with some DSC data takenalso at BENSC during the time of the neutrondiffraction experiment, we were able to construct atentative magnetic phase diagram for the series(figure 1).

Figure 1. Tentative magnetic phase diagram forYbMn2Si2-xGex. The shaded area indicates thevalence transition region (see text). The labellingof the magnetic phases is taken from [3, 4].

All samples with a Ge concentration below x =1.4 show similar magnetic behaviour exhibitingcollinear antiferromagnetic ordering at hightemperatures with Yb ordering at temperaturesbelow around 6 K, as suggested earlier [5].

Figure 2. Thermal evolution of the (110)-peakintensities of YbMn2Si0.4Ge1.6.

There is evidence for a valence transitionaround a Ge concentration of x ~1.6 as indicated bythe thermal evolution of the peak intensities of the(110) reflection (figure 2). Below ~ 150 K thispeak starts to split into two (110) reflectionscharacteristic of a phase separation into Yb2+- andYb3+-based phases. While the Yb3+ phase ofsmaller a-lattice constant decreases (a ~ 3.92 Å at20 K), the content of the Yb2+ phase of larger a-lattice constant increases (a ~ 3.96 Å at 20 K). Athigher Ge concentrations (x = 1.8) the valencetransition temperature shifts to higher temperatures.

[1] A. Szytula and J. Leciejewicz, Handbook of CrystalStructures and Magnetic Properties of Rare Earth Intermetallics(CRC Press, Boca Raton, 1994)[2] I. Nowik, I. Felner and E. R. Bauminger, J Magn MagnMater, 185 (1998) 91[3] M. Hofmann, S.J. Campbell and A. Szytula, J. AlloysComp. 311 (2000) 137[4] M. Hofmann, S.J. Campbell, A.V.J. Edge and A J Studer, J.Phys. Cond. Matter 13 (2001) 9753[5] M. Hofmann, S.J. Campbell and A.V.J. Edge, Appl. Phys.A (accepted for publication 2001)

57


EXPERIMENTAL REPORT Proposal N° PHY-01-1060Instrument E6Neutron diffraction study of magnetic phase

transition in mixed crystal Mn0.94Fe0.06WO4 Local Contact N. Stuesser

Principal Proposer: D.Sangaa, N. Stuesser Date(s) of Experiment

Experimental Team: H. Ehrenberg Technological University of DarmstadtH. Weitzel Technological University of DarmstadtN. Stuesser BENSC, HMI, BerlinD.Sangaa, National University of Mongolia

July 11-13, 2001

Date of Report: February 10, 2002IntroductionFirst studies on the crystal structure and themagnetic ordering in the series of mixed crystals (MnxFe1-x)WO4 were performed in the 1960s and1970s[1]. In the mixed system (MnxFe1-x)WO4 twodifferent antiferromagnetic phases were observed inrange 0.12<x<0.32[2,3].Recently, it was found that a 12 % substitution ofFe on the Mn position leads to an interestingcompetition between and a coexistence ofinterpenetrating magnetic structures related to thepure systems MnWO4 and FeWO4 [4]. This coexistence cannot be related to sampleinhomogenieties. These different types of magneticordering can be qualitately understood by lookingto the different superexchange paths between theMn-Mn, Mn-Fe and Fe-Fe for small contentrationFe or for 6 % substitution of Fe in mixed crystal(MnxFe1-x)WO4. For MnWO4 analysis of magnondispersions allowed to derive nine couplings viaone or two oxygens[5]. The couplings for FeWO4are not yet known quantitatively.

Experiment The powder diffraction pattern at a natural sampleof Mn0.94Fe0.06WO4 was collected on the E6-multcounter diffractometer using a double focusingpyrolytic graphite monochromator at wavelength λn= 2.44 Ǻ in the temperature range between 17 and1.5 K Rietveld analyses of the magnetic and nuclearstructures were then carried out with the FullProfprogram[6]. ResultsOur neutron diffraction experiments show that themagnetic structures of Mn0.94Fe0.06WO4 at lowtemperatures are closely related to the pure MnWO4(see Fig. for preliminary Rietveld fits) In MnWO4. two incommensurate magnetic phases,AF2 between 8 K and 12.3 K and AF3 between12.3 K and 13.5 K, were reported in [1].The absence of an AF2–like phase inMn0.94Fe0.06WO4 is probably related to theinfluence of the Fe+2 ions anisotropy, as suggestedin [4], which may suppress a magnetizationcomponent along the b-axes.

Fig..Examples of neutron powder diffractogram with Rietveldfit and difference plot for Mn0.94Fe0.06WO4 at temperatures15.1 , 12 K.

References[1] Lautenschlaeger G, Weitzel H, Vogt T, Hock R, Boehm A, Bonnet M and Fuess H 1993 Phys.Rev. B48 6087 and references therein[2]. Obermayer H A, Dachs H and Schroecke H 1973 Solid State commun. 12 779[3]. Ding Y et al 2000 Physica B 276 596[4]. Stuesser N et al 2001 J.Phys.:Condens. Matter 13 2649[5]. Ehrenberg H, Weitzel H, Fuess H and Hennion B 1999 J.Phys.:Condens. Matter 11 2753[6]. Rodriguez-Carvajal J, FullProf: a program for Rietveld refinement and pattern matching analysis Abstract of the Satellite Meeting on Powder Diffraction on the 15th Congress of the IUCr (Toulouse,1990) p 127

58


EXPERIMENTAL REPORT Proposal N° Eigenf.Instrument E6Incommensurate magnetic order in

ErFe2Al10 Local ContactN. Stüsser

Principal Proposer: M. Reehuis, Universität Augsburg Date(s) of ExperimentExperimental Team: A. Krimmel, Universität Augsburg

A. Loidl, Universität AugsburgM.W. Wolff, W. Jeitschko, Universität Münster

16.7.2001 – 18.7.2001


The ternary compounds LnFe2Al10 (Ln = Tb,Dy Ho Er) crystallize in the orthorhombic spacegroup Cmcm. Below the Néel temperatures TN= 16.5 K and TN = 7.5 K the terbium anddysprosium moments in TbFe2Al10 andDyFe2Al10 are ordered antiferromagnetically.[1]. No magnetic order could be detected forthe isotypic holmium and erbium compoundsdown to 1.6 K. This behaviour may berationalized by the much weakermagnetocrystalline anisotropy of the holmiumand erbium ions. A neutron powder diffractionstudy revealed that the terbium anddysprosium moments show incommensuratemagnetic order with the wave vectors k = (0,0.7977, 0) and k = (0, 0.7836, 0), respectively[2]. TbFe2Al10 shows a square-wave modulatedmagnetic ordering of the terbium sublatticewith a moment direction parallel to the a-axis.In DyFe2Al10 the dysprosium moments rotatewithin the ac-plane forming a helical magneticstructure.

In order to investigate the magnetic order ofErFe2Al10 a neutron powder experiment hasbeen carried out on the diffractometer E6.Powder patterns were collected at 100 mK and1600 mK using a dilution refrigerator. The usedneutron wavelength was = 2.45 Å. In thepowder patterns the nuclear and magneticreflections were observed to be relativelyweak. The difference plot (Fig. 1) finallyshowed well the presence of magneticreflections. It could be seen that all thesepeaks appear at same 2-positions as foundearlier for TbFe2Al10 and DyFe2Al10. Thus, themagnetic structure can be also described witha propagation vector k = (0, ky, 0), where ky isexpected to be ~0.8. From Rietveldrefinements we obtained the value ky =0.791(2). Due to the poor signal to noise ratiothe data did not allow us to distinguishbetween the presence of a sinusoidal or ahelical magnetic structure. However, for us it is

Fig. 1: Difference between the total intensitiesof ErFe2Al10 collected at 100 mK and 1500 mK.

important to see that the magnetic structure ofErFe2Al10 can be descibed with the samepropagation vector of the terbium and thedysprosium compound. Using the same type ofmagnetic order of DyFe2Al10 the experimentalmagnetic moment exp = 6.8(5) B can beobtained.

References

[1] V.T. Thiede, T. Ebel, W. Jeitschko, J.Mater. Chem. 8 (1998) 125.

[2] M. Reehuis, B. Fehrmann, M.W. Wolff, W.Jeitschko, M. Hofmann, J. Magn. Magn.Mater. 276-278 (2000) 594.

10 15 20 25

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59


EXPERIMENTAL REPORT Proposal N° *Instrument E8Influence of alternating magnetic fields on

the Bloch walls in a Nickel single crystal Local Contact W. Treimer

Principal Proposer: W. Treimer, TFH Berlin and HMI Date(s) of ExperimentExperimental Team: J. Peters, HMI

A. Hilger, TFH Berlin May – September2001


In the past, the influence of external fields andforces on the Bloch wall thickness in a Nickelsingle crystal has been studied. Indeed, aNickel single crystal has a regular magneticstructure of domains and Bloch walls inbetween when placed in a static externalmagnetic field. The thickness of the Blochwalls can be estimated by measuring therefraction of unpolarised neutrons with thedouble crystal diffractometer E8 (see BENSCreport 2000).If one superposes now an alternating magneticfield with an amplitude similar to themagnitude of the static magnetic field to thislast one, the Bloch walls begin to move [1]. W.Döring showed that this motion gives rise to anextra term of the energy density of the wall andthus to an enhancement of the Bloch wallthickness. If, in addition, the velocity of motionbecomes comparable to the velocity of theneutrons, the path of the neutrons through theBloch wall can be decreased or enhanced,depending on their direction of motion.

It is known from former experiments at E8 [2],that the part of refracted neutrons (e.g. the twoweak maxima neighbouring the main peak infig. 2) is related to the Bloch wall thickness.Thus one expects that the intensity of therefracted neutrons should depend now on thefrequency of the alternating field.

In a first step, the Nickel single crystal wasplaced in the static magnetic field of 2 mT. Theneutron intensity reflected at the analyser, keptin the maximum position of the rocking curve,in dependence of the angle between theBloch walls and an axis perpendicular to thescattering plane was measured (see fig. 1). Ifthe Bloch walls are parallel to the neutronbeam, no refraction occurs. This situationcorresponds to the central peak in fig. 1.

Inte

nsity

Angle

Fig. 1: Intensity depending on the rocking angle of theNickel single crystal.

Now a glancing angle of 70 min of arc waschosen and a series of rocking curves wasmeasured with the additional alternatingmagnetic field at different frequencies. Theresults are shown in fig. 2 for three differentfrequencies up to 1 kHz. No significant changeof the refracted intensity relative to the integralintensity could be observed. Alternating fieldsof frequencies higher than 1 kHz, which seemto be necessary to produce the predictedeffects, could not be realised up till now.

-60 -40 -20 0 20 40 60

1

frequency of AC 0 Hz 0.5 kHz 1.0 kHz

Nor

mal

ised

Inte

nsity

Angle in arcsec

Fig. 2: Intensity depending on the rocking angle of theanalyser

[1] W. Döring, Z. Naturforsch. A3 (1948) 373[2] J. Peters, W. Treimer, Phys. Rev. B64 (2002) 214415

60


Name(s) Affiliation

Proposal Nº

Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

Crystalline- and magnetic structure offerroelectric persovskites

(100) corresponding to the RE-(4b) site, (101) givenby the Mn-moments and (102) which is built up by acombination of the crystallographic, Mn-magneticmoments and RE-magnetic moments for TmMnO3 andTm0.25Lu0.75MnO3.

The presence of the (100) line in the “diluted” samplefour times smaller in intensity then of the parentcompound indicates that RE is occupyingpreferentially the (4b) site and still aligning in the Mn-magnetic ordering via an exchange interaction. Wealso can conclude that RE-moments are aligned alongc-axis only and they are antiferromagnetically coupled.

In the course of the experiment carried out on E9 wemeasured TmMnO3 in high temperature regime. Thissample should exhibit a ferroelectric transition around300C from the P63cm to P63/mmc. The diffractionpattern was fitted using Fullproof trying both spacegroup mentioned above. At 1100C we still can noticethe presence of the (216) intensity, which belongs tothe ferroelectric symmetry. The Oxygen-bi-pyramidsnearby the Mn-atoms does never reach a straightconfiguration and they are still tilted enough to have amirror plane on the Mn-(a,b) plane and probably stillgiving rise to a small polarization (in the microscopicmeaning) while NO macroscopic polarization canbe detected any more at high temperature.

[1] N.A. Hill, J. Phys. Chem. 104 (2000) 6694[2] W.C. Koehler, et al., Phys. Letters 9 (1964) 93[3] M. Fiebig, et al., Phys. Rev. Lett. 84 (2000) 5620.[4] M. Fiebig et al. , Appl. Phys. Letters 77(2000)4401[5] A. Munoz et al., Phys. Rev. B62 (2000) 9498[6] K.Kritayakirana et al. Optics Comm 1(1969) 95

E6/E9

R. Feyerherm

PHY01-985

G.J. Nieuwenhuys, Leiden University

D.G. Tomuta, G.J. Nieuwenhuys, Leiden UniversityR. Feyerherm, HMI

May 3-13, 2001

10 September, 2001

The rare-earths and yttrium manganites, REMnO3,with RE = Ho, Yb, Er, Tm, Lu and Y crystallize in thehexagonal structure, space group –polar class ofP63cm. The same system exhibits two types of tran-sition: at low temperature an antiferromagnetictransition and at higher temperature a ferroelectrictransition [1]. There are predictions in the literaturethat the ferroelectric ordering is associated with astructural transition from noncentrosymmetrical P63cmto a centrosymmetrical P63/mmc. The ferroelectricordering occurs at 913 K for YMnO3, 873K forHoMnO3, 573 K for TmMnO3 and at 983 K forYbMnO3 .

We have investigated the magnetic structures ofTmMnO3, ErMnO3 and of YbMnO3 at lowtemperatures and some “diluted” similar systems suchas RE0.25Lu0.75MnO3, RE0.25Y0.75MnO3 (RE:Tm andYb).We know from our previous results on LuMnO3and from ref.[2,3,4,5] that the Mn-sublattice can havecompletely different arrangements of the spins withrespect to the crystallographic axes and thus LuMnO3is different then YMnO3. The absence of the (100)line in the LuMnO3 indicates a magnetic space groupP6’3c’m.For REMnO3 the rare earth atoms can carry a magneticmoment, but directed along c-axis only. From opticalexperiments [6] it is known that there is an exchangeinteraction of the Mn magnetic lattice with the RE atthe (4b) position. Our experiments on polycrystallinesamples show an alignment of the RE momentsthrough a nonzero and increasing intensity of the (100)magnetic reflection. This is not due to the reorientationof the Mn-moments as observed in ScMnO3 [5] sincethe intensity of the (101) given by only the Mn-moments should consequently decrease. Our specificheat data on these samples show an anomaly occurringbelow TN indicating a splitting of the ground state witha gap between 25-50K. We deduce from the heatcapacity data an entropy change in zero externalmagnetic field, which indicates the splitting of adoublet of two thirds of the RE-ions, that is thefraction occupying the (4b) sites. If we assume thatthe alignment of the RE moments is given only by the(4b) site we try to understand the behavior of thediluted samples.In fig 1. we show the intensities of three reflections:

61


Name(s) Affiliation

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Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

Crystalline- and magnetic structure offerroelectric persovskites

28 30 32 34 36 38 40 42 44 46 48 50 520

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Fig.1.High temperature diffractograms during cooling down.

On the other hand we investigated the magnetictransition at low temperature. We measured beforesome “diluted” compounds focusing on the (100) linecorresponding to the RE-site and (101) given by theMn-moments. As we reported before we are trying tounderstand the RE- occupancy of the two differentsites- 4b-site -which in TmMnO3 sample seems to bethe significant one for the exchange interaction- andthe second crystallographic site (2a). This time wetried to fill only the 4b–site, knowing that the LuMnO3and TmMnO3 have the same magnetic symmetry ofP6’3c’m. We made sample of Tm0.667Lu0.33MnO3. Ourpreliminary results show a preferential 4b-occupancyof the Tm (~ 95%), which we infer from the fact thatthe intensity of (100) is comparable with that of theparent compound.

[1] N.A. Hill, J. Phys. Chem. 104 (2000) 6694[2] S.C.Abrahams, Acta. Cryst.B 57, (2001) 485[3] H.L.Yakel et al, Acta Cryst. 16, (1963) 957[4] K. Lukaszewicz et al., Ferroelectrics 7, (1974) 81[5] D.G.Tomuta et al, J.Phys., Cond Matt 13, (2001)[6] M. Fiebig, et al., Phys. Rev. Lett. 84 (2000) 5620.[7] M. Fiebig et al. , Appl. Phys. Letters 77(2000)4401[8] Th.Lonkai et al, submitted to Appl.Phys.A

E9

R. Feyerherm

PHY-01-1064

G.J. Nieuwenhuys, Leiden UniversityD.G. Tomuta, Leiden UniversityR.Hendrikx, Leiden UniversityR. Feyerherm, HMI

30 October-6November,2001

4 February, 2001

The rare-earths and yttrium manganites, REMnO3,with RE = Ho, Yb, Er, Tm, Lu and Y crystallize in thehexagonal structure, space group–polar class of P63cm.This class of materials shows a coexistence of twodifferent type of behavior: ferroelectricity andantiferromagnetism [1]. The ordering temperatures forthese behaviors are about 1000K (for YMnO3- 920Kand 80K, HoMnO3- 873K and 73K etc), respectively. On E9 we have investigated the high temperatureferroelectric transition for LuMnO3, which wasreported recently to be of order ~1000K as for theother REMnO3 [2,3]. It was also reported [4] theYMnO3- high temperature phase measured by X-Raydiffraction is characterized by the absence ofreflections with h+2k 3n. Although we are aware ofthe ferroelectric properties at room temperature ofthese materials the origin of the ferroelectric state orthe presence of the local electric dipole moments arestill unknown. Sample preparation has proven already verysuccessful. With respect to the powder samples,comparing to literature data, it appears that oursamples are indeed of very high purity. Thepreparation technique requires a solid state reaction ofthe cation oxides (Lu2O3, MnO2) by calcination in air-or O2 –flow for 12 h.[5] During our attempt in collecting the diffractogramsof high temperature LuMnO3 we have noticed thedecomposition of the sample with temperature. Weassume that the decomposition for the smaller RE-ionic radius is inherent using the set-up of theavailable furnace at HMI. The sample has to be invacuum. Since we are measuring compounds ofperovskite type of structure, the O2-content may play amajor role in the properties of these compounds. Wecould follow the decomposition of the startingLuMnO3 into other phases by identifying new Braggreflections in the diffractograms. Since, by passing theferroelectric state to a paraelectric state, the symmetryof the compound should increase (with a mirror plane)we expect a complete disappearance of somereflections. By pumping continuously at hightemperature we conclude that O2 was leaving thestructure. This leads us to multiple secondary phases.We present one of the “new” peaks present at hightemperature and on all diffractograms during coolingdown the sample to room temperature.

62



Instrument E6Crystalline- and magnetic structure offerroelectromagnetic perovskites Local Contact

R. Feyerherm

Principal Proposer: G.J. Nieuwenhuys, Leiden University Date(s) of ExperimentExperimental Team: D.G. Tomuta, Leiden University

G.J. Nieuwenhuys, Leiden UniversityR. Feyerherm, HMI

12-19 Nov. 2001

Date of Report: Jan. 21, 2002

The rare-earths and yttrium manganites,REMnO3, with RE = Ho, Yb, Er, Tm, Lu and Ycrystallize in the hexagonal structure, space groupP63cm and belong to the rare class [1] of ferro-electric materials. There are predictions in theliterature that the ferroelectric ordering should beassociated with a structural transition fromnoncentrosymmetrical P63cm to acentrosymmetrical P63/mmc. The ferroelectricordering occurs at 913 K for YMnO3, 873K forHoMnO3 , 573 K for TmMnO3 and at 983 K forYbMnO3 .

In former experiments we have investigated themagnetic structure of the Mn-ions. In the case ofYMnO3 and HoMnO3, that has also been done bythe Tübingen group [2]. From our experiments itbecame clear that in the case of magnetic rare-earthelements the magnetic moment of the rare-earth-ionis aligned by the ordered Mn structure via anexchange interaction. The presence of thisinteraction was already known from opticalexperiments [3], but is also the subject of recentwork by Fiebig et al.[4]. Where the alignment ofTm and Yb is clearly seen from the intensity of the(100) diffraction line in powders, the alignment ofHo and Er is not or hardly visible. On the otherhand, specific heat and SR (muon spin resonance)experiments showed clear evidence of suchinteraction in the latter cases. During the present experiment we have investigatedthree single crystals (Tm-, Yb- and ErMnO3) , andobtained detailed temperature dependences of themost important lines. In fig.1 we present our resultsfor Tm- and YbMnO3, fig.2 displays the indeedweak lines observed in ErMnO3. The other aim of the present experiment was toinvestigate the dependence of the intensity of themagnetic diffraction on an external field. From ourmagnetization measurements we know that a spinflip occurs in YbMnO3 at 3 tesla directed along thec-axis, and Fiebig’s Faraday effect has shown thesteps and hysteresis in ErMnO3. Unfortunately, themagnet HM1 cannot reach the necessary field whilemounted on E6. We are glad to have now beamtimeallocated on E4 to carry out these measurements.

0 50 100 150 200

0

25

50

75

100

Sqr

t(Int

ensi

ty)

T

YbMnO3 (101)

YbMnO3 (100) TmMnO3 (101) TmMnO

3 (100)

Fig. 1 The temperature dependence of the squareroot ofthe intensity of the (100) and (101) lines in YbMnO3 andin TmMnO3.

0 20 40 60 80 1000

20

40

60

80

ErMnO3

Sqrt(

Inte

ntisi

ty)

T

(101) (100) (102)

Fig. 2 The temperature dependence of the squareroot ofthe intensity of the (100), (101) and (102) lines inErMnO3.

References:

1. G.A. Smolenskii and I.E. Chupis, Sov. Phys.Usp 25 (1982) 475

2. Th. Lonkai, et al., to be published3. K. Kritayakirana et al., Optics Communications

1 (1969) 954. M. Fiebig et al., Phys. Rev. Lett. 88 (2002)

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% >" ( * % * )( % , * + % , ) ' ) '( + ) & )%%% - & , + (( % * %%

23 / .>?@

23 0 / #D>?#.@

64


EXPERIMENTAL REPORT Proposal N° PHY-01-1072Instrument E9*Phase Transitions and Phase Separation in

La(1-x)Ca(x)MnO(3-x/2) (0<x<0.5) Local Contact Dr.Daniel M.ToebbensDr .Michael Tovar

Principal Proposer: Prof.Henryk Szymczak,IPh, PAS, Warsaw, Date(s) of ExperimentExperimental Team: Prof.Henryk Szymczak,IPh, PAS, Warsaw

Dr.Michael Tovar, BENSC *9-16 August 2001

Date of Report: January 23, 2002*Astonishing magnetic and electrical properties of thehole doped manganites become a subject of numerousexperimental and theoretical investigations.Reasons ofthis interest are various linkages of the properties ofmetals and insulators, ionic and covalent crystals withintermediate ion valence, systems with spin, orbital andcharge ordering and, at last, systems which can undergoa phase separation. These properties result from a closeinterplay of lattice, charge and spin degrees of freedomthat gives rise to a complex phase diagrams for theseclasses of compounds [1]. It is believed that the doubleexchange (DE) interaction between Mn3+ - Mn4+ pairscontrols magnetic and electrical properties of perovskitemanganites [2,3]. This model is based on the realexchange of eg electrons between two partially filled dshells of Mn3+ and Mn4+ ions. However, the facts existwhich cannot be explained by DE alone [4].Goodenough [5] has suggested that ferromagnetism inthis class of compounds is not governed by DE alone butalso by the specific nature of the superexchangeinteractions in the Mn3+ - O – Mn3+ and Mn3+ - O – Mn4+

Jahn-Teller ion systems. Many recent experimentalresults have presented experimental demonstrations ofthe existence of a spatial phase separation in manganites[6]. The phase separation is associated with the fact thatthe itinerant charge carries prefer the ferromagneticordering rather than the antiferromagnetic one becauseof the energy gain (see for example [7]). If theconcentration of the carriers is low they are collected insome regions of the sample and generate theferromagnetic order. It is clear that the peculiarities ofMn ions play a key role in the magnetic and electricalproperties of the hole-doped manganites by providingmagnetic moments and charge carriers. Therefore it isinteresting to investigate La1-xCaxMnO3-y compoundsdepending on the formal average manganese valence.The Mni+ / Mnj+ (where i, j = 2, 3, 4) ratio can bechanged by various methods [8]. Until now thedependence of magnetic and magnetoresistanceproperties of the hole-doped perovskite manganites onoxygen stoichiometry has been weakly investigated.Very intriguing magnetic and magnetoresistanceproperties have been recently revealed for La1-

xCaxMnO3-y [9] compounds with oxygen vacancies. Ourinvestigations have shown the unconventional featuresfor these strongly reduced manganites such as: largeferromagnetic component and magnetic orderingtemperature as well as large magnetoresistance in spiteof the absence of Mn3+ - Mn4+ pairs. The oxygenvacancies are supposed to be ordered. In this project wehave performed magnetic and neutron diffractionmeasurements in order to establish the magnetic phase

diagram. Polycrystalline La1-xCaxMnO3 (0 ≤ x ≤ 0.50)samples have been fabricated with conventional ceramictechnology. The topotactic reaction method was used tochange oxygen content in synthesized compounds. Allsynthesized compounds have been checked by powderX-ray diffraction method to determine qualitative phasecontent and unit cell parameters. Neutron diffractionmeasurements for La0.5Ca0.5MnO3-y sample have beenperformed in BENSC using the E9 neutron powderdiffractometer (FIREPOD) with wavelength of neutrons = 1.79686 Å and scanning step 0.002 0. Asapphire single crystal filter of total thickness of 110mm in the primary beam has been used to reduce thenumber of epithermal neutrons. In order to increase theneutron flux at the sample a vertically focusing Riso - design Ge-monochromator has been used.Compositions of the La0.50Ca0.50MnO3-y series are foundto undergo a number of concentration phase transitionsin the ground state with decreasing oxygen content.Antiferromagnetic state of y= 0 transforms intoferromagnetic one at y= 0.02 which in turn convertsinto cluster spin glass state at y 0.10. At y= 0.12 a newtype of ferromagnetic phases appears. The content ofthis ferromagnetic phase is the highest for thecomposition y= 0.30. We suppose that at y ≥ 0.30 theeffect of phase separation is observed (the samplesconsist of antiferromagnetic medium and ferromagneticclusters). To explain the obtained experimental resultsthe oxygen vacancies are supposed to be disordered aty 0.15 whereas in the vicinity y~ 0.25 there is a trendto the vacancies ordering in microdomains having aform of thin planes (this conclusion was confirmed byHREM observations). For compositions with oxygencontent close to y= 0.50 the oxygen vacancies orderingcorresponds to Sr2Fe2O5 structure. In conclusion, we have shown that oxygen vacanciesin La0.5Ca0.5MnO3-y are ordered for y≥ 0.3 anddisordered for y≤ 0.2. This ordering effect isresponsible for peculiar properties of the stronglyreduced manganites.

References[1] A.Urushibara et al.,Phys.Rev.B 51(1995)14103[2] C.Zener, Phys.Rev. 82(1951)403[3] P.-G. De Gennes, Phys.Rev. 118(1960)141[4] I.O.Troyanchuk et al., Phys.Rev.B58(1998)2422[5] J.B.Goodenough et al.,Phys.Rev. 124(1961)373[6] G.Papavassilou et al.,Phys.Rev. B59(1999)6390[7] E.L.Nagaev , Physica B (1995)6390[8] S.V.Trukhanov et al.,LowTemp. Phys. 27(2001)247

[9] I.O.Troyanchuk et al., JETP 120(2001)183

65


EXPERIMENTAL REPORT Proposal N° EFInstruments E6, E9Magnetic structure of Mn(dca)2(pyz-d8)

and other molecular magnets Local Contact

Principal Proposer: R. Feyerherm, A. Loose, HMI Date(s) of ExperimentExperimental Team: & P. Smeibidl, S. Raasch, D. Többens, HMISample preparation: J. L. Manson, ANL Argonne

T. Ishida, Univ. for Electro-Communication, Tokyo

25.5.-27.5.,11.6.-18.6.,20.7.-23.7.,13.8.-18.8.


Molecular magnetism is an area of increasinginterdisciplinary interest. Magnetic solidsbased on the dicyanamide ion, [N(CN)2]-,abbreviated (dca), such as M(dca)2 [M = V, Cr,Mn, Fe, Co, Ni], have shown interesting bulkmagnetic behavior [1-3]. Mn(dca)2 iscomprised of high-spin S = 5/2 Mn2+ ions thatare arranged on a rutile-like crystal lattice. Acanted antiferromagnetic state sets in below16 K while the Ni-analog is a ferromagnetbelow 21 K.Alteration of the crystal lattice can be achievedby introducing auxiliary organic bridgingligands. Mn(dca)2(pyz) is such an example andcontains 2D Mn(dca)2 arrays that are heldtogether by pyrazine (pyz) ligands to yield aReO3-like 3D network structure [4]. The longorganic spacer ligands promote formation oftwo interwoven lattices. The ensuing magneticproperties are expectedly very different fromthose of parent Mn(dca)2. Collecting highstatistics powder neutron diffraction data onthe diffractometer E6, we have revealed thelong-range magnetically ordered structure inthis complex solid.

Fig. 1: Difference of the of the E6 neutron powderdiffraction spectra taken below and above themagnetic ordering temperature, showing severalBragg reflections of magnetic origin. The data canbe fitted with the model of the magnetic structuredepicted in Fig. 2, assuming an ordered moment at1.5 K of 4.5(1)B.

Zero-field magnetic structure of Mn(dca)2(pyz-d8)as determined from neutron powder diffraction.

Magnetic-field dependent measurements onthe powder sample (using VM3) revealed theexistence of two critical fields, Hc1 = 0.4 T andHc2 = 3 T, which we associate with the criticalfields for H parallel and perpendicular to theordered moments, respectively.

Further materials that were studied areMn[C(CN)3]2, Fe(dca)2(pym) (pym=pyrimidine)and Fe(dca)2(pym)THF-d8. Mn[C(CN)3]2 ordersmagnetically below 1.18 K and appears tohave a complex incommensurateantiferromagnetic structure, which could not besolved yet. Further data analysis is inprogress.The other mentioned compounds appear toexhibit simple antiferromagnetic orderingbelow about 2.5 K. However, due to the largecontent of hydrogen in the pyrimidine ligands,the data quality is limited. Synthesis ofdeuterated samples is envisaged.

References

[1] J.L. Manson et al., Inorg. Chem. 38, 2552 (1999). [2] C. R. Kmety et al., Phys. Rev. B 62, 5576 (2000). [3] J. L. Manson et al., Chem. Mater. 10, 2552 (1998). [4] J. L. Manson et al., J. Amer. Chem. Soc. 123, 162(2001).

10 20 30 40 502(°)

Inte

nsity

(a.u

.)

I(1.5K) - I(3K)2

1

0

66


EXPERIMENTAL REPORT Proposal N° EFInstrument E6, E9Magnetic phase diagram of Mn1-xFexWO4Local Contact

Principal Proposer: Elvira Garcia-Matres Univ. Augsburg Date(s) of ExperimentExperimental Team: Norbert Stüßer HMI 26.2-27.2, 31.3-1.4,

12.7-14.7, 6.8-12.8,8.10-10.10, 4.12-5.12.


Pure FeWO4 and MnWO4 are isostructural andcrystallize in the monoclinic space group P2/c.Differences in lattice constants amount only toabout 1% and the Mn1-xFexWO4 system shows ahomogeneous mixing. The MnWO4 compoundforms two antiferromagnetic incommensuratecollinear magnetic structures between 13.5 Kand 12.3 K, and between 12.3 K and 8.0 K,respectively. Both structures have the samepropagation vector k = (0.214, 1/2, 0.543),however, differ with respect to the orientationof the moments. The magnetic ground statebelow 8 K is commensurate withk = (1/4, 1/2, 1/2) [1]. The collinearantiferromagnetic spin arrangement in FeWO4below TN = 76 K is described by k = (1/2, 0, 0).A mixed crystal of compositionMn0.88Fe0.12WO4 shows simultaneouslydifferent types of long range magnetic orderrelated to the magnetic structures of the purecompounds MnWO4 and FeWO4 [2]. We foundstrong evidence that the two different structuresare formed on the same lattice with onestructure embedded as a cluster within thesecond structure. This unusual behaviour oftwo interpenetrating magnetic structuresbecomes possible by the various superexchangecouplings between adjacent Mn-Mn, Fe-Fe,and Mn-Fe via one or two intervening oxygenions.In 2001 we have extended our investigations ofthe complex magnetic behaviour to sampleswith increased Fe-concentration using neutronpowder diffraction. The main results aresummarized in the phase diagram shownbelow. Between a concentration of 19% and21% Fe the spins order in the FeWO4-typestructure at higher temperature and undergo amagnetic phase transition to the commensurateMnWO4-type ordering at lower temperatures.No indications were found for anincommensurate structure which is present at

Fe-concentrations less equal 12%. Verysurprising was the observation of anincommensurate MnWO4-type spinarrangement at Fe-concentrations between 24%and 29%. This structure occurs at lowtemperatures, has a wavevector of(0.21 1/2 0.54), and is superimposed on thedominating FeWO4-type spin ordering. Anincommensurate spin arrangement with thiswavevector was only found for the pureMnWO4 so far. Besides magnetic structuredetermination data analyses of pattern collectedat the high resolution powder diffractometer E9indicated magnetoelastic effects in the mixedcrystals. Comparative measurements at MnWO4and FeWO4 were carried out too.

magnetic phase diagram including themagnetic propagation vectors

[1] Lautenschläger G et al. 1993 Phys. Rev. B48 6087-6098 and references therein[2] Stüßer N et al. 2001 J. Phys.: Cond. Matter13 2753-2766

0.00 0.05 0.10 0.15 0.20 0.25 0.300

5

10

15

20

25

30

(0.21 1/2 0.54)

(0.23 1/2 0.51)(kx 1/2 kz)(1/2 0 0)

(1/2 0 0) + (0.21 1/2 0.54)

(1/4 1/2 1/2)

Mn1-xFexWO4

Tem

pera

ture

[K]

concentration x

67


Name(s) Affiliation

Proposal Nº

Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

Magnetic structures in RETiGe (RE = Dy, Ho, Er)compounds

E9

D. Többens

EF

K. Prokes HMI

K. Prokes HMIK.H.J. Buschow UvA, Amsterdam, The Netherlands

June 2001

20.1.2002

Recently, new group of rare-earthintermetallic compounds RTiGe have beendiscovered. They crystallize in the tetragonalCeFeSi-type of structure (space groupP4/nmm) that can be described as a R-Ge-Ti2-Ge-R sequence of layers propagatingalong the tetragonal axis [1]. While Ti atomsoccupy in this structure the special 2(a) site at(0,0,0), rare earth and Ge atoms occupy 2(c)site at (¼,¼,z). There are two atoms of eachkind in the crystallographic unit cell.

Neutron-diffraction data at werecollected between 1.7 and 240 K for DyTiGe,between 1.7 and 130 K in the case of HoTiGeand between 1.7 and 60 K in the case ofErTiGe. The fits, comprising scale factor, cellparameters, crystallographic-positionparameters, background, peak-profileparameters and isotropic thermal factorsconfirmed the CeFeSi-type of structure ofthese compounds. As the temperature islowered below the magnetic phase transitiontemperatures, new Bragg reflections appear inspectra of all three samples that are assumedto be of magnetic origin. All the additionalreflections recorded at 1.7 K can be explainedby assuming that the magnetic structure has apropagation vector q = (0, 0, 0.5).

The magnetic moments are coupledwithin the unit cell ferromagnetically in allthree compounds, however moments in theadjacent unit cells along the c axis areoriented antiparallel to those in the originalone. The magnetic structure can be describedas “+ + + + ” sequence along thetetragonal axis. In the case of Dy and Hocontaining samples, the moments were foundto be oriented along the tetragonal axis, whilein the Er sample perpendicular to the c axis

(note the difference in the low-angle range inspectra shown below). Refined moments at1.7 K were found to be equal to 10.04 (9),9.15 (8) and 8.45 (9) µB/RE atom for Dy, Hoand Er, respectively if the RE3+ magneticform factor was supposed to be of the form<j0>. Use of the <j0>+c2<j2> form led to a

20 40 60 80 100 120 140

-200

0

200

400

600

800

1000

1200

1400DyTiGeT = 1.7 K

C

ount

s

2 (deg)

20 40 60 80 100 120 140

0

2000

4000

6000

8000

10000

12000

14000

ErTiGeT = 1.7 K

Cou

nts

2 (deg)

Fig.: DyTiGe and ErTiGe low-T spectra.

better agreement with the data, however, alsoto a lower magnetic moments that weretypically 15% smaller than the free-ionvalues. This suggests possible influence ofcrystal fields.

Reference[1] S.A. Nikitin, I.A. Tskhadadze, I.V. Telegina,A.V. Morozkin, Yu.D. Seropegin, J. Magn. Magn.Mater., 182 (1998) 375.

68

EXPERIMENTAL REPORT

BENSC

Principal Proposer:

Experimental Team:

Proposal No

Instrument

Local Contact


Date of Report

Search for antiferromagnetic vortex cores

in YBa2Cu3O6:54

HM Rnnow, DRFMC, CEA, France

B Lake, Oak Ridge Nat. Lab., USANB Christensen, Ris, DenmarkNH Andersen Ris, Denmark

PHY-02-291

V2/Flex

P. Vorderwisch

December 18-22, 2000

March 1, 2001

The existence of antiferromagnetic correlations and

uctuations in the high temperature superconducting

cuprates has stimulated considerable work both exper-

imentally and theoretically. For instance, it has been

proposed that the superconducting and antiferromag-

netic order parameters are in fact two components of

one SO(5) superspin1. In addition to being a means

of describing the doping phase diagram, the SO(5)

theory can give predictions for the vortices induced

by a magnetic eld.2;3;4. In the core of the vortices,

the superconducting order parameter vanishes, which

according to the SO(5) theory can happen either by a

vanishing of the entire superspin order parameter or

by ipping the superspin into the antiferromagnetic

plane. Assuming vortices to comprise linear chains of

weakly coupled antiferromagnetic disks, we estimated

that signicant correlations along the vortices would

only occur well below 1 K. On this basis, we proposed

to search for such antiferromagnetically ordered vor-

tex cores at dilution refrigerator temperatures in un-

derdoped YBa2Cu3O6:54.

However, few days before the experiment, it became

known that an elastic antiferromagnetic signal had

been observed at zero eld in other crystals with sim-

ilar doping5;6. The reported signals sets in between

200 K and 300 K, and experience a slight increase be-

low Tc

. With this new knowledge at hand, the com-

plication of using a dilution unit was abandoned in

the belief that a eld eect would show up at Tc

.

The 1.44 g single crystal of YBa2Cu3O6:54 was ori-

ented with with the superconducting planes perpen-

dicular the horizontal eld of the 4 T cryomagnet

HM2. Be-lters were used both before and after sam-

ple to completely eliminate =2 contamination. In-

deed, we found elastic scattering at the antiferromag-

netic wave vector, as depicted below. The signal per-

sisted above Tc

up to at least 100 K, but due to the

time constraints for the experiment, focus was kept on

a possible eld eect below Tc

. Figure 1 compares the

observed scattering at respectively zero eld and at

4 T. However, there is no observable eect of the mag-

netic eld. We currently work to establish whether

the signal observed in the present experiment is of

the same origin as that reported by Sidis et al. and

by Mook et al.5;6.

Several theories of the high-Tc

cuprates identies

the pseudogap region with occurrence of so called or-

bital currents within the CuO plaquets7;8. It is pos-

sible that the elastic signal under investigation is due

to such orbital currents. But on the other hand, it

has been suggested that it is due to small volumes

of an antiferromagnetic phase caused by hydration of

the samples9;10. This possibility will be investigated

by measuring any hydrogen content of the crystal by

prompt gamma activation analysis. Subsequently, it

will be attempted to dehydrate the crystal.

In summary, an elastic signal has been observed

at the antiferromagnetic wavevector in underdoped

cuprates. The present experiment showed, that this

signal is not aected by a magnetic eld. We note,

that this does not exclude the original hypothesis, that

the magnetic eld can generate antiferromagnetic vor-

tices, which become correlated at very low tempera-

tures. However, the presence of a zero eld signal

renders the detected of antiferromagnetic vortex cores

very diÆcult.

0.8 0.9 1 1.1 1.2350

400

450

500

550

600

650

700

(0.5,0.5,Ql)

Cou

nts/

6min

0 T4 T

[1] S.-C. Zhang. Science 275, 1089, 1997

[2] D. P. Arovas, A. J. Berlinsky et al. Phys. Rev.

Lett. 79, 2871, 1997

[3] H. Bruus, K. A. Eriksen et al. Phys. Rev. B 59,

4349, 1999

[4] N. A. Mortensen, H. M. Rnnow et al. Phys. Rev.

B 62, 8703, 2000

[5] Y. Sidis, C. Ulrich et al. cond-mat/0101095

[6] H. A. Mook, P. Dai et al. cond-mat/0102047

[7] C. M. Varma. Phys. Rev. B 55, 14554, 1997

[8] S. Chakravarty, R. B. Laughlin et al. cond-

mat/0005443

[9] A. V. Dooglav, A. V. Egorov et al. LETP Lett.

69, 792, 1999

[10] H. Alloul, 2001. private communication

69


EXPERIMENTAL REPORT Proposal N° PHY-02-298Instrument V2/FlexVortex core signal in the single layer high-

temperature superconductor La2-xSrxCuO4 Local Contact P. Vorderwisch

Principal Proposer: D.F. McMorrow, Risø National Lab, Denmark Date(s) of ExperimentExperimental Team: B. Lake, Oak Ridge National Laboratory, USA

N.B. Christensen, K. Lefmann, Risø Natl LabG. Aeppli, NEC Research Institute, USA

12-26/2/2001

Date of Report: Jan 16th 2002

There is strong evidence that magneticinteractions play a crucial role in themechanism driving high-temperature super-conductivity in cuprate superconductors. Toinvestigate this we have done a series ofneutron scattering measurements on super-conducting La2-xSrxCuO4 (LSCO) in an appliedmagnetic field using the V2/FLEX neutronscattering spectrometer at HMI.

For our measurements we used under-doped LSCO (x=0.10, Tc = 29 K). Below thesuperconducting transition temperature (Tc),the field penetrates the superconductor via anarray of normal state metallic inclusions orvortices. Phase coherent superconductivitycharacterized by zero resistance then sets inwhen the vortices freeze into a lattice at thelower field-dependent irreversibility temper-ature (Tirr).

We find that the elastic anti-ferromagnetic signal observed in zero field issignificantly enhanced by application of a fielde.g. a factor of three at H=14T, see figure 1a[1]. The Néel temperature for the field-inducedsignal coincides with Tc. The magnetic in-planecorrelation length (>400Å), is much greaterthan the superconducting coherence length(~20Å). Since the superconducting coherencelength gives the size of the vortices themagnetism cannot reside in the vortex coresalone, but must extend beyond them andpossibly into the superconducting regions ofthe material.

Our results imply that in underdopedLa2-xSrxCuO4 the vortices nucleate largeantiferromagnetic and possibly insulatingregions. If these regions overlap they may wellpin each other giving rise to long-rangemagnetic order below Tc. Superconductivityexists in the remaining interstitial regions whichare disconnected from each other. It is unclearwhether antiferromagnetism and super-conductivity co-exist immediately outside thevortex cores or whether this region is purelyantiferromagnetic. This second possibility hasrecently been predicted by the ‘SO(5)’ theory

of superconductivity. Newer versions of thistheory have allowed the SO(5) symmetry to berelaxed so that co-existence of super-conductivity and magnetism can occur [2,3].Such models give quantitative agreement withour data, as shown by the fitted line in fig. 1b.

Figure 1 The temperature and field-dependence of the ordered spin moment squared.The data have been calibrated using a transverseacoustic phonon and are presented in units ofB

2/Cu2+. (a) shows the temperature-dependence.The zero-field signal is marked by the blue circlesand the dashed line is a guide to the eye. Alsoplotted is the field-induced signal for various appliedfields (equal to the signal measured in field minusthe zero-field signal). The solid lines through thedata are fits to mean-field theory. (b) shows thefield-induced signal as a function of field at T=2K.The solid line is a fit to theory [3].[1] B Lake, HM Rønnow, NB Christensen, G Aeppli,K Lefmann, DF McMorrow, P Vorderwisch, PSmeibidl, N Mangkorntong, T Sasagawa, MNohara, H Takagi, TE Mason Nature 415 299 2002.[2] J-P Hu, & S-C Zhang. LANL preprint servercond-mat /0108273 (2001).[3] E Demler, S Sachdev, & Y Zhang, Phys. Rev.Lett. 87, 067202-067205 (2001).

70


EXPERIMENTAL REPORT Proposal N° Phy-02-322Instrument V2/FLEXVortex State in underdoped La2-xSrxCuO4Local Contact Peter Vorderwisch

Principal Proposer: B Lake, ORNL USA and Oxford University UK Date(s) of ExperimentExperimental Team: HM Rønnow, DRFMC, CEA, ILL, France

NB Christensen DF McMorrow, Risø DenmarkG Aeppli, NEC Research Institute, USA

1-13/10/2001

Date of Report: 17th Jan 2002

There is strong evidence that magneticinteractions play a crucial role in themechanism driving high-temperaturesuperconductivity in cuprate superconductors.To investigate this we have done a series ofneutron scattering measurements onsuperconducting La2-xSrxCuO4 (LSCO) in anapplied magnetic field using the V2/FLEXneutron scattering spectrometer at HMI.

For our measurements we used under-doped LSCO (x=0.10, Tc = 29 K). In thesuperconducting phase this compounddevelops long-range antiferromagnetic order[1]. Recent work has shown that application ofa magnetic field to the sample greatlyincreases the magnetic ordering. The Néeltemperature for the field-induced signalcoincides with Tc. The signal in thesuperconducting plane is resolution limitedcorresponding to a correlation length, >400Å[2].

In this experiment we investigated thedependence of both the zero-field and field-induced signal with wavevector perpendicularof the superconducting plane. The crystal wasoriented so that the superconducting planes lievertical and pass through the horizontalscattering plane. The horizontal magnet HM1was used for this measurement and the fielddirection was perpendicular to thesuperconducting plane.

We find that both the zero-field andfield-induced antiferromagnetic ordering areindependent of the component of wavevectorout of the superconducting plane. The datawhich was collected across several differentBrillouin zones shows that the ordering is two-dimensional within the errorbars (see figure 1).

Figure 1 Magnetic intensity at theincommensurate position (1.1175,K,0.1175) asa function of wavevector (0,K,0) perpendicularto the superconducting plane. Data collectedover several different Brillouin zones is shown.Zero-field signal is represented by the greensquares while the signal measured at H=6T isrepresented by the blue the circles.

[1] Kimura H. et al. Phys. Rev. B 59, 6517-6523 (1999).[2] B Lake, HM Rønnow, NB Christensen, GAeppli, K Lefmann, DF McMorrow, PVorderwisch, P Smeibidl, N Mangkorntong, TSasagawa, M Nohara, H Takagi, TE MasonNature 415 299-302 (2002).

71



Instrument E1Neutron diffraction study of the field inducedorder in singlet-ground state magnet CsFeCl3 Local Contact

H. A. Graf

Principal Proposer: Mitsuru Toda, KUR Date(s) of ExperimentExperimental Team: Yutaka Fujii, Fukui Univ.

Shinji Kawano, KURJens Klenke,Hans Anton Graf, M. Steiner,HMI

10 / 2001

Date of Report: 30 Jan. 2002

A hexagonal compound CsFeCl3 is a typicalsinglet-ground-state system with a fictitiousspin S = 1 of a Fe2+ ion, characterized by alarge positive single-ion anisotropy D. Becauseof predominance of the effect of the anisotropyenergy over that of the exchange interactions,the ground state is nonmagnetic down to zeroK. However, in the presence of an externalmagnetic field H applied along the c-axis, asuccessive phase transition occurs, and thethree dimensional long-range order (3D-LRO)appears around the level crossing field Hc (=7.5 T), where the lower level Sz=+1 of theexcited doublet crosses the ground state Sz=0.Recently, the field induced order in the singletground state system TlCuCl3 (dimer spinsystem) is noticed as the realization of theBose Einstein condensation (BEC) of themagnetic excitation[1]. The nature of the fieldinduced order is considered as the ordering ofmixed two states; and from this point of view,we might consider the field induced order inCsFeCl3 as BEC, either. Previously, we have performed neutronscattering experiments at HMI and JAERI, andsucceeded in observing the incommensuratestate at H < Hc

[2]; however, due to the largemagnetic torque, we have not succeeded inthe experiments at H > Hc. Therefore, the firstpurpose of the experiment is the observation ofthe incommensurate (IC) state in the fieldregion of H > Hc; and the second purpose ofthis work is to clarify the possibility of therealization of BEC of the magnetic excitation inCsFeCl3. Figure 1 shows the field dependence of theintegrated intensity of neutron magneticscattering at T=1.55 K. Firstly, the IC phaseappears at around 5 T, and following the IC-commensurate (C) phase transition, themagnetic scattering increases and decreasesalmost symmetrically with respect to Hc in theC phase. Then, at the phase boundary around10 T, we have observed the IC-state, whosedistribution map of neutron counts is similar tothat obtained in the IC phase at around 5 T.

Fig.1 Field dependence of the integratedintensity of neutron magnetic scattering.

Next we measured the temperaturedependence of the magnetic scattering at 6.5T, 7.0 T, 7.5 T, 8.0 T and 8.5 T, anddetermined the critical exponent of thetemperature dependence of the magneticmoment Mx.

Fig.1 Temperature dependence of theintegrated intensity of neutron magneticscattering at 7.0 T, 7.5 T, 8.0 T and 8.5 T.

The critical exponent of Mx () showed the fielddependency; and it is noticed that the value of was about 0.33 at 6.5 T and 8.5 T, which isvery near to the value 0.35, predicted by thetheory of BEC[1].

[1]T. Nikuni et al.: Phys. Rev. Lett. 84 (2000) 5868.[2]M. Toda et al.: J. Phys. Soc. Jpn. 70 (2001) Suppl. A154.

72

EXPERIMENTAL REPORT

BENSC

Principal Proposer:

Experimental Team:

Proposal No

Instrument

Local Contact


Date of Report

Suppression of quantum uctuations

by a magnetic eld

M. Enderle, K. Prokes Institut Laue-Langevin, HMI Berlin

M. Enderle, Institut Laue-Langevin, Grenoble, France

K. Prokes HMI, Berlin, Germany

EF

E4

K. Prokes

15-22/7/01

31/1/02

CsNiCl3 is a quasi-1D Heisenberg antiferromagnet(AF) of Ni2+ spins 1 which are strongly coupled alongthe hexagonal c-direction and weakly perpendicularto c. The interchain exchange J

0 is strong enough todestroy the Haldane ground state of the ideal spin-1Heisenberg AF chain which is a macroscopic spin sin-glet and cause 3D order. However, the spin dynamicsof CsNiCl3, even in its ordered phase, shows a veryunusual behaviour, which at low elds is reasonablydescribed by a hybridisation of Haldane-ground statetype quantum spin dynamics and classical transversespin waves [1]. This description implies an increaseof the AF order parameter with increasing magneticeld, opposite to the behaviour of a classical AF. Aprevious experiment showed that this picture breaksdown above 4 T, and the spin dynamics resemblerather the pure 1D case [2].Here we investigate the eld dependence of severalmagnetic and nuclear Bragg peaks of both CsNiCl3and its classical counterpart, CsMnI3, up to 17 T us-ing VM-1 with Dy-insert on E4. CsMnI3 has the samemagnetic and crystallographic structure as CsNiCl3and similar exchange constants but Mn2+ spins 5

2and

therefore much more classical behaviour. Its excita-tions at zero and low magnetic elds are well describedby transverse spin waves.Figure 1 shows the eld dependence of various Braggpeaks of CsNiCl3 and CsMnI3. The integrated in-tensities of the rocking scans are normalised to thesmallest eld value for comparison. A small variationof intensity with eld is observed for all Bragg peaksof CsMnI3, no matter whether magnetic or nuclear.This probably results from a slight misalignment anda small movement of the sample in the eld. Thenuclear Bragg peaks of CsNiCl3 show no eld depen-dence at all, while the magnetic Bragg peaks all in-crease by the same factor of about 2. Hence the inten-sity increase cannot result from a change of the mag-netic structure or domain structure. It cannot resultfrom extinction eects either as the magnetic Braggintensity is much smaller than the nuclear Bragg in-tensities - which do not change with eld. Hence theonly remaining explanation is an increase of the anti-ferromagnetic order parameter itself. The zero-eldsuppression of the AF order parameter of CsNiCl3has been attributed to the zero-point occupation oftransverse spin waves. This should yield a similareect in CsMnI3. Moreover, spin wave theory pre-dicts a decrease of the order parameter with increasing

eld. We therefore conclude that the suppression ofthe order parameter of CsNiCl3 results from quantum uctuations precursing the Haldane ground state sin-glet. A magnetic eld suppresses this quantum groundstate in favour of long-range antiferromagnetic order.The much more classical and half-integer spin systemCsMnI3 does not experience these quantum uctua-tions and therefore does not show any peculiar elddependence of its magnetic order parameter.

0 5 10 15 200.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Applied Field [T]

inte

grat

ed I

nten

sity

CsNiCl3

(−1/3 −1/3 −1)(2/3 2/3 −1)(−1/3 −1/3 −3)(0 0 −2)(1 1 0)

0 5 10 15 200.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Applied Field [T]

inte

grat

ed I

nten

sity

CsMnI3

(1/3 1/3 −1)(1/3 1/3 1)(2/3 2/3 −1)(1/3 1/3 −3)(0 0 −2)(1 1 0)

Figure 1: Magnetic eld dependent intensities of various anti-

ferromagnetic and nuclear Bragg peaks of CsNiCl3 and CsMnI3.

[1] I. Aeck and G.F. Wellman, Phys.Rev.B 46, 8934 (1992).

[2] M. Enderle et al., Phys.Rev.B 59, 4235 (1999); Exp.rep.

PHY-02-242(2000).

73


EXPERIMENTAL REPORT Proposal N° PHY-01-1050 PHY-01-1051Instrument E6/E9The interplay between crystal structure and the spin-

gap in low-dimensional oxides under high-pressure. Local Contact D. Többens, N. Stüßer

Principal Proposer: A. Lappas, FORTH/IESL, 711 10 Heraklion, Greece Date(s) of ExperimentExperimental Team: C.J. Nuttall, A. Lappas, FORTH/IESL

D. Többens, HMIJ. Hernandez-Velasco, N. Stüßer, HMI

07. 11 – 11. 11. 200112. 11 – 13. 11. 2001


The magnetic properties of low-dimensional quantumantiferromagnets (AF) have attracted a lot of interestboth from theoretical and experimental point of view [1].Among a variety of quasi-1D or 2D compounds we havecarefully selected the PbNi2-xAxV2O8 (A=Mg) material,which although it displays a Haldane gap in the spinexcitation spectrum (for x=0), it is on the other handcritical towards the formation of long-range ordered(LRO) Néel state [2]. We focus then on low-dimensionalmagnetic models embedded in a three-dimensionallattice. Our earlier neutron diffraction studies (BENSCProposal: PHY-01-948) have shown unambiguously thatthe impurity-induced magnetic exchange interactions, inx>0 solid-solutions, are of long-range character and themagnetic phase transitions are of Néel type (e.g. maximumTN~3.5 K). The present proposal requested 4 days on E6and 1 day on E9 diffractometers to continue the study oftheir magnetic phase diagram but through a differentroute, that of external pressure. The latter has beenproved before a valuable tool to probe importantstructural changes in a lattice. Therefore we planned toinvestigate how spin-gap compounds can be drivenacross the transition to LRO by application of pressure,instead of doping with other impurities. At BENSC,instead of using only the temperature as a “variable” toalter the elastic and/or magnetic properties of the solids,we wished to employ high-pressure (P10 kbar) as aunique “probe” to search for lattice distortions thatpromote structural phase transitions and modulate themagnetic exchange interactions in selected low-dimensional inorganic compounds. The scheduledbeamtime planned to initially explore the previous effecton the magnetic state of the PbNi2-xAxV2O8 series -A=Mg, with x= 0, 0.04. However, only 2.5 days wereused for high-pressure diffraction experiments.Unfortunately, as first-time users of the high-pressure(P<10 kbar) and low-temperature (1.8<T<300 K) setup atBENSC, we encountered a number of technical problemsthat had to do with the actual design of the high-pressurecell. It was proved that the cell could not hold high-pressures (P>1 bar) at cryogenic temperatures (T~1.7 K).Finally, the cell failed completely (one of the pistons wasbroken) and the proposed experiments were unable to becarried out. Despite these drawbacks, in Figures 1 and 2 wepresent some preliminary information on our high-pressurework. We look forward to see the re-commissioning of theparticular setup in order to achieve optimum ‘calibration’of the high-pressure cell and learn to control its behaviourat low-temperatures. This will be very important especiallyfor diffraction experiments that search, for example, forpressure-induced changes in chemical systems that display

small staggered moment magnetism (e.g. of <>~ 1 B, asin the case of PbNi2-xMgxV2O8) or undergo structuralphase distortions that are accompanied by smallsuperstructure peaks – effects difficult to detect in a high-background diffraction data.

[1] G. Chaboussant, P.A. Crowell, L.P. Levy, O.Piovesana, A. Madouri, and D. Mailly, Phys. Rev. B 55,3046 (1997).[2] Y. Uchiyama, Y. Sasago, I. Tsukada, K. Uchinokura,A. Zheludev, T. Hayashi, N. Miura, P. Boni, Phys. Rev.Lett. 83, 632 (1999).

0 20 40 60 80 1000

200

400

600

800

'Flutec' in 6mm V-canT~40 KIn

tens

ity (a

.u.)

2 (deg)

0

2000

4000

6000

8000

CuBe empty cellT~55 K

Fig. 1. Diffraction patterns (E6) from the high-pressureCuBe cell (top) and the pressure medium, ‘Flutec’,(bottom) at λ=2.444 Å.

25 35 45 55 65 750

1x104

2x104

3x104

4x104T=1.7 K P~ 3.5 kbar

'outside cryostat'

PbNi2V2O8

NaCl

Inte

nsity

(a.u

.)

2 (deg)

Fig. 2. Observed, calculated and difference Rietveldplots for a tentative P~3.5 kbar (E6; λ=2.444 Å): itshows a two-phase refinement (Rwp=13.6%, χ2=13) of alimited 2θ-range with Bragg peaks from both PbNi2V2O8and NaCl (the pressure calibration material) at 1.7 K.

74


EXPERIMENTAL REPORT Proposal N° PHY-02-280Instrument FLEXQuantum Critical Field Investigations in the

Unconventional S=1/2 Antiferromagnet TlCuCl3 Local Contact P. Vorderwisch

Principal Proposer: N.Cavadini, LNS ETH Zurich & PSI Date(s) of ExperimentExperimental Team: N.Cavadini, Ch. Rüegg, LNS ETH Zurich & PSI

P. Vorderwisch, P. Smeibidl, BENSC HMI 15.01-01.02.2001


Increasing interest is devoted to the occurrence ofquantum phase transitions in solid state physics.Theoretical efforts on the one side and experimentalinvestigations on the other side increasinglyconcentrate on quantum magnetism as an idealtesting ground for novel predictions. Unfortunately,the microscopic input from neutron scatteringsuffers from intrinsic limitations dictated by theavailability of suitable samples. S=1/2 TlCuCl3 isan exception of actual relevance. Wellcharacterized by INS investigations in zero-field asa linked dimer compound, it features a singletground-state and a finite spin gap to triplet excitedstates, [1] and references therein. The modestenergy gap /gB=6T allows access to a quantumcritical point, which denotes in the present case the“T=0” phase transition from quantum disorder tofield-induced order. Detailed susceptibility andhigh-field magnetization results provide aconsistent picture of the ordered state in terms ofBose-Einstein condensation of the triplet states [2].Neutron diffraction investigations determined thepropagation vector and the value of the staggeredmagnetization M=0.26B per Cu2+ at H=12T [3].Extending the neutron investigations to the excitedstates, we performed an INS study of the spectrumin the field range 0<H<12T at the lowesttemperature. A description of the instrumental set-up and preliminary account of the experimentalresults is presented in the following. Measurementswere performed on the cold neutron spectrometerFLEX, operated at fixed final energy Ef=4.7meVwith a cold Be filter in front of the analyzer. Alarge TlCuCl3 single crystal oriented in thescattering plane spanned by the (020) and (104)Bragg reflections was mounted in the VM-1cryomagnet and kept at T=1.5K. Above Hc=6T, thefield dependent profiles observed at Q=(0 4 0) r.l.u.consist of two sharp transitions, corresponding tothe renormalized |10’ and |1-1’ Zeeman states(Figure 1). Additional low-lying intensity detectedat H=12T will be described in the following.Regarding the main transitions, a simple picturebased on pertubed dimer states in an effectivehamiltonian captures the experimental observations,under consideration of

H HD HZ HMF

where HD denotes the zero-field dimer interactionterm, HZ the external Zeeman term, HMF thestaggered internal mean-field term. The latteraccounts for the field-induced transverseantiferromagnetic order [3] and is responsible forthe mixing of the elementary dimer states,justifying the observed spectral transitions. Withinthis model, an additional low-lying spectraltransition between the renormalized |11’ and |00’states is expected. Unfortunately, a careful analysisof the quasi-elastic signal was not possible underthe adopted experimental settings. The extent towhich the perturbative dimer picture approximatesthe collective quantum critical features in TlCuCl3strongly depends on the agreement of the expectedlowest transition with experiment. At present,evidence for broad low-lying intensity is reportedfrom the measurements performed at H=12T.Additional efforts are planned to investigate thenature of the ground state and lowest excited statesin greater detail under high resolution conditions.

Figure 1. Observed excitation energy of the tripletmodes at the minimum of the dispersion band,

across the quantum critical point Hc=6T.

[1] N.Cavadini et al., Phys. Rev. B 63, 172414(2001)[2] A.Nikuni et al., Phys. Rev. Lett. 84, 5868(2000)[3] H.Tanaka et al., J. Phys. Soc. Jpn. 70, 939(2001)

75

EXPERIMENTAL REPORT

BENSC

Principal Proposer

Experimental Team

Proposal No

Instrument

Local Contact

Dates of Experiment

Date of Report

Excitations in the higheld phase of CuGeO

HM Rnnow M Enderle CENGCEA Institut LaueLangevin

HM Rnnow DRFMC CENG CEA Grenoble FranceM Enderle Institut LaueLangevin Grenoble FranceK Habicht HMI GermanyP Smeibidl HMI Germany

PHY

VFlex

K Habicht

Feb th Mar th

March th

In the spinPeierls system CuGeO coupling ofthe quasi onedimensional spin system to the latticeleads to an instability with respect to dimerizationboth of the magnetic system and the lattice BelowTSPK the spins S

form a macroscopic quan

tum ground state related to the dimer state wherethe spins form pair states with S Simultaneously the spins of a pair move closer to each otherCuGeO dimerizes along c the direction of strongestantiferromagnetic exchange The interaction with thelattice leads to a threedimensionally ordered phasewith Bragg reections at

k k integer rather than

the total minimumof the dispersion of the mag

netic excitations The excitations are pairs of domainwalls that separate the two equivalent realizations ofthe ground state The lowestlying excitations of thedimer chain form a triplet of welldened sharp boundstates which are separated from the ground state byan energy gap The dispersion of this triplet revealsthat the magnetic interchain interactions prefer ferromagnetic alignment of the Cu spins along a andantiferromagnetic alignment along b The triplet excitation at kAF

splits sym

metrically up to T Above the critical eldof about T where the lowest excitation was expected to become soft incommensurate magnetostructural superlattice reections are observed This incommensurate modulation can be imagined asa frozen periodic pattern of former domainwall excitations and is described in detail in The maximum magnetic contribution and negligible structuralcontribution is observed on

Previous experiments on V investigated the magneticexcitations around the antiferromagnetic zone center

and close to the incommensurate superlattice

peaks

The lowest excitation at the dis

persion minimum does not become entirely

soft but remains at meV Slightly above the critical eld two new lowlying excitations were observedThe same two modes apart from a shift to higher energies which corresponds to the aaxis dispersion areobserved at

Their dispersion along c has its

minimum at the commensurate wave vector

where also the spectral weight is concentrated Thesetwo modes are identied as the transverse magneticexcitations which introduce and remove onedomain wall pair in the higheld phase In addition a lowlying mode IC was found with minimumenergy meV and maximum spectral weight at

the wave vector of the incommensurate superlatticereections

Theory expects such an in

commensurate mode either at much higher energymin

min

min

with gBH at thecommensurate wave vector or at zero energy phasonIn the present experiment elastic and inelastic

studies of the higheld incommensurate magneticstructure and excitations were performed in the theh h plane the h plane and the k plane again using the vertical T cryomagnet VM The elastic part tested the intensity of the superlattice reections at T in dependence of temperaturebetween K and about mK Data were takenwith the dilution insert between K and mK between K and K the standard sample rod wasused The superlattice Bragg intensity saturates already around K Together with earlier experiments this conrms that the amplitude of the staggeredmagnetization remains smaller than expected byeld theory down to lowest temperatures Strong relaxation phenomena upon fast cooling from high temperatures were observed at low temperatures well inexcess of thermal relaxation times of the dilution sample holderThe inelastic part was performed with guideS

kf A xed and KBelter in kibefore the monitor At high energy transfer datawere taken with ki xed to A The eld dependence of IC was investigated in energy scans at

at T T

and T In spite of afactor variation in the incommensurability and thevariation of the magnetic eld the energy of IC didnot change at all However the integrated intensityincreased by a factor of between T and TIn order to connect the previous ndings around

and

constant qscans were taken

along h and h

at T With

we conrm that disperses with the weak

ferromagnetic exchange along h as anticipated With

the dispersion of IC and could be

followed To our big surprise IC increases with decreasing h crosses and can be followed all the wayto h where it has an energy of meV gBH

Figure This seems to imply that the two incommensurate modes and the phason which have beenconsidered as dierent excitations by theory are infact one mode

76

cnr

Again at T a preliminary study of the dispersion away from

was performed This con

rms that IC indeed has its minimumat

while the energy of increases from

to

To summarize our results on the dynamics We observe an incommensurate excitation IC the minimumenergy of which is eldindependent It is almostsoft at the IC Bragg peak position like a phason hasa hdispersion opposite to the commensurate excitations and an energy of gBH at the antiferromagnetic wave vector as expected for the longitudinalexcitation

0 0.1 0.2 0.3 0.4

0.5

1

1.5

2

2.5

Q=(h,1,1/2−δ)

Ene

rgy

[meV

]

Figure Dispersion of magnetic excitations of CuGeO alongh

at T K where

JG Lussier et al JPhysCondensMatter L LP Regnault et al PhysRevB V Kiryukhin et al PhysRevB HM Rnnow M Enderle DF McMorrow LP Regnault G Dhalenne A Revcolevschi A Hoser K ProkeschP Vorderwisch and H Schneider PhysRevLett M Enderle HM Rnnow DF McMorrow LP RegnaultG Dhalenne A Revcolevschi P Vorderwisch and H Schneider submitted to Phys Rev Lett condmat

77

URu2Si2-HMI-report-2 // brandt // 28.01.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N¡ PHY-02-283

Instrument V 2 Study of the tiny ordered magnetic moment in URu2Si2

in high magnetic field.Local ContactK . H a b i c h t & K . P r o k e s

Principal Proposer: F . B o u r d a r o t , C E A - G r e n o b l e Date(s) of ExperimentExperimental Team: B . F k , C E A - G r e n o b l e

G . A m o r e t t i , U n i v e r s i t d i P a r m a R. Caciuffo, Universit di AnconaP . S a n t i n i , O x f o r d P h y s i c s

18->25-6-2001

Date of Report: 2 8 - 0 1 - 2 0 0 2

Th e aim of t his ex pe riment was to me asu re th ema gn eti c f ie ld dep en den ce up to 17 T of th e tin yor de red ma gn eti c moment an d the ma gn eti cex ci tat ion s in the h eav y-fe rmion su pe rco ndu ct orURu2 Si2 . The re sul ts of th es e meas ur eme nts a reimpo rta nt fo r t he un der sta nd ing of p hys ica l pro per ti esof t his sy st em and will al lo w t o d is cri min at e b etwee ndi ff ere nt th eor ies a cco rdi ng to th e symmet ri es of th ehi dd en ord er pa ramet er.Th e exp eri me nt was v ery su cc ess ful . The ex ci tat ion swe re me asu re d a t t he wa ve ve cto rs Q=(1,0,0 ) and Q=(1 .4,0,0 ) in a mag net ic fi eld of 1 7 T (cf Fig. 1&2) .As e xpe cte d, th e mag net ic ex cit ati on en erg y atQ=(1 ,0,0) incr eas es wi th fi eld , a s pre vio us lyob se rve d i n lower fi eld s, wh ile th e exc ita ti on atQ=(1 .4,0,0 ) dec rea se s s lig ht ly in en erg y. Th ese re su lts ar e in agr ee men t wit h t he cr yst al el ect ric f iel dsc he me dev el ope d b y us [1] .

Fig.1: Mag ne tic ex citation at Q =(1 ,0,0) me as ure d o n FLEX a nd IN 14 fo rdiff ere nt ma gne tic f ield

Fig.2: Mag ne tic ex citation at Q =(1 .4 ,0 ,0 ) me as ure d o n FLEX a nd IN 14 fo rdiff ere nt ma gne tic f ield

Th e mea sur ement s o f the fi el d d epe nd enc e o f the ma gn eti c moment we re mo re di ffi cul t due to t hewe ak nes s o f the si gn al compa red to t he bac kg rou nd.De sp ite th e low co un tin g s ta tis tic s, ne w a nd ve rysu rp ris ing r esu lts were ob ta ine d, wh ich su gg est th at th e hid den o rde r p ar ame ter i n URu2Si 2 b re aks ti me -re ve rsa l s ymmet ry [2 ], in co ntr adi ct ion wi th ma ny of th e pre sen t the ori es on URu2Si 2.It woul d b e hig hly i nte res ti ng to co nti nue t hes eme as ure men ts an d d et ermine t he tra ns iti onte mp era tur e for th e mag net ic mo men t at fie ld s a bov e15 T.

Fig.3: Magnetic Bragg peak at Q=(1,0,0) for different magnetic fieldsup to 17T.

[ 1] P. Sa nt ini , G. Amor ett i, R. Ca ci uff o, F.Bo ur dar ot, a nd B. F k, Ph ys. Rev. Le tt . 8 5, 65 4(2 00 0)[2 ] N. Sha h, P. Ch an dra , P. Col ema n, an d J . A.My do sh, Ph ys . Rev. B 61 , 5 64 (2 000 )

100

120

140

160

180

200

220

240

-1.5 -1 -0.5 0 0.5 1 1.5

0 T, 2 K8 T, 2 K13.2 T, 2 K14.5 T, 2 K17 T, 2 K17 T, 25 K

Cou

nts

/Mon

.=10

6

ωωωω-ωωωωQ = (1 0 0)

(Deg.)

URu2Si

2

Q = (1 0 0)

Flex V2

0

200

400

600

800

1000

1200

10

20

30

40

50

60

70

1 2 3 4 5 6

H = 0 T, IN14

H = 12 T, IN14

H = 17 T, FLEX V2

Inte

nsit

y (A

rb. U

nits

Mon

it.=

1000

0)

Intensity (Arb. U

nits Monit.= 5.5*10

6)

Energy (meV)

URu2Si

2

Q = (1.4 0 0)

IN14 & Flex V2T = 2 K

0

200

400

600

800

1000

1200

10

20

30

40

50

60

1 2 3 4 5

URu2Si2Q = (1 0 0)


H = 0T IN14

H = 12T IN14

H = 0T FLEX

H = 17T FLEX

Inte

nsit

y (A

rb. U

nits

. Mon

it.=

1000

0)

Intensity (Arb. U

nits. Monit.= 5.5*10

6)

Energy (meV)

0

200

400

600

800

1000

1200

10

20

30

40

50

60

1 2 3 4 5

URu2Si2Q = (1 0 0)


H = 0T IN14

H = 12T IN14

H = 0T FLEX

H = 17T FLEX

Inte

nsit

y (A

rb. U

nits

. Mon

it.=

1000

0)

Intensity (Arb. U

nits. Monit.= 5.5*10

6)

Energy (meV)

78


EXPERIMENTAL REPORT Proposal N° PHY-02-288Instrument V2Unusual Low-Energy Spin Fluctuations in an

Underdoped HTC Superconductor Local Contact Klaus Habicht

Principal Proposer: B. Keimer, Max-Planck-Institut FKF, Stuttgart Date(s) of ExperimentExperimental Team: C. Ulrich, Max-Planck-Institut FKF, Stuttgart

T. Keller, Max-Planck-Institut FKF, StuttgartK. Habicht, HMI, Berlin

30.4.01 – 12.5.01

Date of Report: 28.1.2002In general, the antiferromagnetic andsuperconducting phases of the cooper oxidehigh-TC superconductors are considered to bewell separated. In previous polarized andunpolarized elastic neutron scatteringexperiments at a conventional triple axisneutron spectrometer at the Orphee reactor inSaclay we found commensurate anti-ferromagnetic ordering in the superconductinghigh-TC cuprate YBa2Cu3O6.5 (TC = 55 K) [1].The antiferromagnetic order developes at ahigh temperature of TN = 310 K and ischaracterized by a large correlation lengtharound 100 Å, but the low temperaturestaggered magnetization remains weak, m0 =0.05 B. Interestingly, the magnetic peakintensity exhibits a marked enhancement at TC.Zero-field muon-spin-rotation (SR)experiments demonstrate that the staggeredmagnetization is not truly static but fluctuateson a nanosecond time scale. These resultspoint toward an unusual spin density wavestate coexisting with superconductivity.The SR results indicate that the observedneutron peak is not strictly elastic. Instead itappears to be indicative of an extremely slowspin dynamics with a temperature dependentcharacteristic frequency that moves into theneutron time window around 310 K, and intothe muon time window only at much lowertemperatures. Due to the finite energyresolution of the conventional triple axisspectrometer of about 1 meV, it was notpossible to determine the lifetime of thequasielastic antiferromagnetic Braggreflections. In order to determine the lifetime of the spinfluctuation as a function of temperature wehave performed a high resolution neutronscattering experiment using the resonant spinecho option on the FLEX triple axisspectrometer at the HMI in Berlin. Thepolarization P()/P0() = exp (-) wasdetermined for various temperatures between10 K and 300 K. Here corresponds to thehalf width at half maximum of a Lorentzian

profile and the spin echo time is determinedfrom the distance of the spin echo coils, thevelocity of the neutrons and the frequency ofthe HF-field inside the spin echo coils. For theexperiment a fixed ki = 1.6948 Å-1 was used.Figure 1 shows the result of the spin echoscan of the antiferromagnetic Bragg Peak (-½,-½ ,0) at a temperature of 60 K. The resultinglinewidth of the quasielastic antiferromagneticBragg peak is = 21 10 eV. Due to theweak intensity of the magnetic signal we wereunfortunately not able to determine thelinewidth of the quasielastic signal at othertemperatures.

Fig. 1: Neutron Spin-Echo scan of theantiferromagnetoc Bragg Peak (-½, -½, 0) ofYBa2Cu3O6.5 taken at T = 60 K. The plot showsthe polarization versus spin echo time . Theinset shows the spin echo signal at afrequency of 50 KHz as a function of the coilposition.

References

[1] Y. Sidis, C. Ulrich, P. Bourges, C.Bernhard, C. Niedermayer, L.P. Regnault, N.H.Andersen,and B. Keimer, Phys. Rev. Lett. 86,4100 (2001).

15 20 25 30 35 40 45 500,01

0,1

12 14 16 18 20 22 24160

180

200

220

240

260

280

300

= 21 ev

(-1/2 -1/2 1) T = 60 K

Pola

rizat

ion

(ps)

50 KHz

(-1/2 -1/2 1) T = 60 K

cnts

(3

000

sec)

coil 4 position (mm)

79

EXPERIMENTAL REPORT

Phase diagram of a novel two-dimensionalquantum heisenberg antiferromagnet


Instrument V2/Flex

Local Contact

P. Vorderwisch


2. 7. - 15. 7. 2001Principal Proposer: C. Broholm, Johns Hopkins Univ., USAExperimental Team: C. Broholm, Johns Hopkins Univ., USA

M. B. Stone, Johns Hopkins Univ., USAP. Vorderwisch, P. Smeibidl, S. Kausche, HMI


Piperazinium Hexachlorodicuprate (PHCC),(C4H12N2)Cu2Cl6, has been shown to be a two-dimensional Heisenberg antiferromagnet with afinite energy gap to excitations in zero magneticfield.[1] This system is a new example of a quan-tum spin liquid system in higher dimensions,D > 1, without a single strong dimer exchangeinteraction. Rather, there are multiple strongspin-spin correlations and geometrical frustra-tion within the magnetic unit cell plays a cen-tral role in stabilizing a spin liquid phase in zeromagnetic field. In an applied magnetic field, thedegenerate triplet excitation of a quantum spinliquid becomes effectively Zeeman split into itsthree components. As the magnetic field is in-creased, the lower branch of the triplet is even-tually driven into the ground state, resulting ina gapless system with a now magnetized groundstate. We have performed a series of experimentsinvestigating the magnetic field versus tempera-ture phase diagram as well as the field depen-dence of the magnetic excitations of this uniquequasi 2-D frustrated spin system.

The system was found to order ferrimagnet-ically at low temperatures and high magneticfields. The ordered structure was determined atT=0.05K and 14.5 Tesla to consist of spins ly-ing predominantly in the plane of the primaryHeisenberg interactions in a frustrated configu-ration. A series of fixed temperature magneticfield sweeps were performed to map out the or-dered phase of the system. This result is shownin the magnetic field versus temperature phasediagram in fig. 1.

For temperatures T ≤ 0.4K we have identifieda reentrant phase transition between the gappedquantum disordered phase and the gapless fer-rimagnetically ordered phase. Field scans werealso performed at 0.2 meV and fixed tempera-

14

12

10

8

H (

T)

6543210T (K)

Long Range OrderedGapless,

Quantum DisorderedGapped,

QuantumDisordered

Gapless,

0.1

2

4

1

2

4

H-7

.4T

6 80.1

2 4 6 81

2 4

Figure 1: Magnetic field versus temperature phasediagram for PHCC. Solid circles represent the tran-sition to long range order as determined from mag-netic field(temperature) sweeps at fixed tempera-ture(field). Solid squares represent the critical fieldat which the spin-gap is closed. Open squares corre-spond to the closing of the spin-gap as determinedfrom pulsed field susceptibility measurements.[2]Lines are guides to the eye. Inset depicts the lowtemperature portion of the magnetic field versus tem-perature phase diagram plotted on a log-log axes toillustrate the reentrant behavior of the ordering tran-sition.

ture. These were used to extrapolate the lowerband of the Zeeman split triplet excitation in or-der to determine the magnetic field at which thespin-gap closes. Through these measurementswe have successfully characterized the magneticnature of a significant portion of the phase di-agram of a two dimensional frustration inducedquantum spin liquid.

References

[1] M.B. Stone, et. al., Phys. Rev. B, 64, 144405(2001).

[2] Pulsed field measurements were performed atthe NHMFL at LANL, USA.

80

csco_hmi_dec01_ver2.doc // brandt // 30.01.02 Seite 1 von 1


Instrument V2Experiment TitleHigh-field excitations in the XY quantum magnetCs2CoCl4 Local Contact

K. HabichtPrincipal Proposer: R. Coldea1 Date(s) of ExperimentExperimental Team C.J. Mukherjee1, R. Coldea1, D.A. Tennant1,2, K. Habicht3,

P. Smeibidl3

1Oxford University, UK, 2 ISIS, Rutherford AppletonLaboratory, UK, 3HMI Berlin

10-16 December 2001,inclusive dates

Date of report: 28 Jan 2002

Introduction. We have recently observed a noveltype of order to disorder transition induced by anapplied field in an XY-like quantum magnet,Cs2CoCl4. In-plane fields suppress antiferro-magnetic order giving way to a “spin liqiuid“phase with no long-range order and where themoments are not yet saturated along the field, seeFig 1. This phenomenology resembles predictionsfor anisotropic quantum chains where non-commuting fields introduce quantum fluctuationsthat eventually suppress order and stabilize agapped spin liquid state [2]. The aim of the presentexperiment was to determine the Hamiltonian ofCs2CoCl4 using a new technique we have recentlydeveloped [3] and to quantify effects of fluctuationson the order in the antiferromagnetic phase.Experiment. A 4.4g single crystal of Cs2CoCl4 wasmounted in a dilution insert with a base temperatureof 50 mK and the vertical 14.5 T cryomagnet wasused to apply fields along a. The V2 spectrometerwas operated with vertically focused PG(002)monochromator and horizontally-focused analyserand fixed kF=1.35 or 1.2 Å-1.Measurements. A field of 4 T was applied to fullyalign the spins and open a gap of 0.3 meV to thelowest excited state. A typical inelastic scan isshown in Fig.2. Two peaks are observed and areassociated with the 2 distinct sites in the unit cell.Similar scans were made to map out the dispersionsthroughout the (b*,c*) plane and typical data isshown in Fig. 2. The fully-aligned eigenstate hasthe unique property [3] that the dispersion is theFourier transform of the exchange couplings, thusenabling us to extract the Hamiltonian directly.Crucial for the stability of the spin liquid phase for2.15 T < B < 2.52 T is the XY anisotropy, whicharises from crystal field effects. To gaininformation on those and how they affect theinteraction Hamiltonian we measured theferromagnetic moment up to 12 T, where theincrease above 2.52 T is entirely due to polarizinghigher-level states.Measurements of the ordered moment parallel andperpendicular to the field in the spin-flop phasebelow 2.15 T were made to quantify how quantumfluctuations affect the total ordered moment. A fullanalysis of the data is currently in progress.

Fig. 3. Dispersion relation along the b* direction in thesaturated phase at B=4 T||a. Only one mode is observedalong this direction. The asymmetric shape of thedispersion indicates frustrated couplings.

[1] M.Kenzelmann et al, Phys. Rev. B (in press 2002).[2] J. Kurmann et al, J.Appl. Phys. 52, 1968 (1981).[3] R. Coldea et al, cond-mat/ 0111079 (2001).

Fig. 1. Phase diagram of Cs2CoCl4. Fields applied alongthe a-axis induce an order to disorder transition at 2.15 Tto a spin-liquid phase stable up to 2.52 T, above whichthe spin moment is fully-aligned along the field.

Magnetic Field (Tesla) || a

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Tem

pera

ture

(mK

)

0

100

200

300

400

Antiferromagnetic

Spi

nLi

quid

?

Paramagnetic

Fully-polarizedlower doublet

Fig. 2. Inelastic scan at Q=(0,0,1) in the saturated phase(B=4 T||a) showing two well-defined magnetic excitations.

81

cscu_hmi_dec01.doc // brandt // 30.01.02 Seite 1 von 1


Instrument V2Experiment TitleStabilization of a 2D fractional quantum spin liquidstate by magnetic field in Cs2CuCl4 Local Contact

K. HabichtPrincipal Proposer: D.A. Tennant1,2 Date(s) of Experiment

Experimental Team R. Coldea2, D.A. Tennant1,2, K. Habicht3, P. Smeibidl3

1 ISIS, Rutherford Appleton Laboratory, UK, 2OxfordUniversity, UK, 3HMI Berlin 3-9 December 2001,

inclusive dates

Date of report: 17 Jan 2002

We have recently discovered a new type of two-dimensional (2D) quantum spin-liquid state in thefrustrated quantum magnet Cs2CuCl4[1]. Amongthe most notable features are: (1) extended 2Dscattering continua at low fields, characteristic offractionalization of conventional spin-1 spin wavesinto pairs of spin-1/2 spinons and (2) an unexplaiedfield-induced T=0 disordered state for inplane (bc)fields (Fig 1). Here we explored the order andexcitations at the transition between this disorderedphase at intermediate fields (2.1T<B<BC) and thefully-aligned ferromagnetic state at high fieldsabove BC=8.02 T, where quantum fluctuations areentirely quenched by the field.

For the experiment we used a 3.7 g single crystal ofCs2CuCl4 mounted in the (ab) horizontal scatteringplane. The V2 spectrometer was operated withvertically focused PG(002) monochromator andhorizontally-focused analyser and fixed kF=1.35 or1.2 Å-1. Temperatures down to 50mK wereachieved using a dilution insert and vertical fields(||c) were applied using the VM1 14.5 T magnet.

The new results are : (1) measurement of themagnon dispersion in the forced ferromagneticphase (Fig 2) above the saturation field BC=8.02 Tand (2) observation of a new incommensurateordered phase for 7.1T<B<BC (Fig. 1). A mostlikely candidate for the spin structure is a fan phase(bc plane) stabilized by a small inplane (bc)anisotropy. This order could be regarded as a Bosecondensate induced by closing the magnon gap atBC. Inter-particle interactions and fluctuationsdetermine how the amount of ordered moment andordering wavevector Q change with the particledensity (measured directly through themagnetization) upon lowering field below BC andthe results are shown in Fig. 3. The order is stableonly for a small range of fields, presumably becasefluctuations become strong enough upon loweringfield to overcome mean-field ordering tendencies.Below 7.1 T no magnetic Bragg peaks could bedetected in large scans across the (a*b*) plane,consistent with a disordered spin-liquid state (Fig1). A full data analysis is currently in progress.

Fig. 1. Magnetic phase diagram: above BC=8.02 T spinsare ferromagnetically aligned along the field (Ferro) andexcitations are magnons with dispersion shown in Fig. 2.Closing the magnon gap at BC induces 3D order (Fan ?).Quantum fluctuations become stronger upon furtherlowering the field and induce a transition to a disorderedSpin-Liquid state below 7.1 T. At lower fields (<2.1 T)mean-field effects stabilise 3D helical order.

Fig. 2. Dispersion in the forced ferromagnetic state(B=12T||c). Solid line is the magnon dispersion for aHamiltonian with frustrated 2D couplings J=0.374meV, J'=0.128 meV and inter-layer J''=0.017 meV.

Fig. 3. (a) Order parameter, (b) ordering wavevectorQ=(0.5+ε)b* and (c) magnetization vs. field (from theintensity of the (420) ferromagnetic reflection).[1] R. Coldea et al, Phys. Rev. Lett. 86, 1335 (2001).

Cyc

loid

SSpin

Liquid Ferro

B (T) || c0 1 2 3 7 8 9 10

T(K

)

0.2

0.4

0.6

Fan?

FerroPeak

Inte

nsit

y(a

rbun

its)

0.0

1.0

2.0

3.0

(b)

(a)

B (T) || c7.0 7.5 8.0

Inco

mm

ensu

ratio

n ε

(2π/

b)

0.02

0.03

0.04

0.05

B (T) || c0 2 4 6 8 10

Mag

netiz

atio

nS c

(arb

.uni

ts.)

0.00

0.05

0.10

0.15k=(1,1.5-ε,0)

Fan ?

(c)

k=(1,1.5-ε,0)

[0,k,0]1.0 1.5 2.0

Ene

rgy

(meV

)

0.0

0.5

1.0

1.5

[h,2,0]0.0 0.5 1.0

B = 12 T || cT < 0.1 K

[1,k,0]1.01.52.0

0.0

0.5

1.0

1.5

(010) (020) (120) (110)

82


EXPERIMENTAL REPORT Proposal N° PHY-02-320Instrument FLEXField-Driven Quantum Criticality

in a S=1/2 Spin Liquid Local Contact K. Habicht

Principal Proposer: N.Cavadini, LNS ETH Zurich & PSI Date(s) of ExperimentExperimental Team: N.Cavadini, Ch.Rüegg, LNS ETH Zurich & PSI

K.Habicht, M.Meissner, S.Kausche BENSC HMI 07.08-19.08.2001


Field-driven magnetic ordering occurs in quantumspin liquids when the Zeeman energy g

overcomes the singlet-triplet energy gap of theelementary excitations. A fertile testing ground forquantum critical theories of actual relevance isdirectly addressed in this case at fixed “T=0”.Recent investigations in S=1/2 TlCuCl3 are apt todemonstrate a quantum phase transition, whoseparameters are completely accessible by neutronscattering, Refs. [1-2]. In a previous experiment, we investigated for thefirst time the dynamic framework of the high-fieldphase in TlCuCl3, see Ref. [3]. Above Hc=6T, thespectrum features main transitions corresponding torenormalized Zeeman modes. The field dependenceof these transitions was well reproduced by apertubative model based on dimers in a staggeredinternal field. Efforts to identify the counterpart ofthe soft Zeeman mode led to the evidence ofadditional low-lying scattering at H»Hc, whichhowever could not be described by the aboveapproach. The present experiment fullycharacterizes the nature of the low-lying magneticexcitations as follows.Measurements were performed on the cold neutronspectrometer FLEX equipped with the VM-1cryomagnet. A major improvement against formerinvestigations was the adoption of a dilution inset,operated for our purpose at fixed 50mK. Thisensured better background suppression and closerquantum critical conditions. Sample mounting andinstrumental settings correspond to those alreadyadopted in the previous experiment. Reducing the temperature from 1.5K to 50mK, thementioned low-lying spectral features is observedto sharpen in (Q,) space. Q scans at constantenergy transfer reveal the presence of stiffharmonic branches emerging from the field-inducedBragg reflections (Figure 1). Their magnetic originis certified by the comparison of the neutronprofiles at H=14T and H=6T (Figure 1, bottom).Above results are interpreted as the evidence forgapless spin wave excitations arising from the field-

induced Néel ordered state. However, two factsrender this interpretation highly nontrivial. On theone hand, the progressively ordered ground state ismanifestly tuned at “T=0” by the applied field only.On the other hand, the “classical” spin wavescoexist in the spectrum with the remains of the“quantum” dimer modes. The relevant questionregarding the typical space and time scalesaccompanying the propagation of the renormalizedZeeman modes and the spin waves in the high-fieldphase of S=1/2 TlCuCl3 clearly motivates furtherexperimental efforts, hopefully contributing to theunderstanding of quantum critical magnets.

Figure 1. Constant energy profiles measured inTlCuCl3 at fixed T=50mK, Q=(0,4,0)+∆q [r.l.u.].Data are vertically displaced for convenience.

[1] H.Tanaka et al., J. Phys. Soc. Jpn. 70, 939(2001) [2] N.Cavadini et al., Phys. Rev. B 63, 172414(2001)[3] Ch. Rüegg et al., Appl. Phys. A, accepted forpublication (2002)

83

Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° *PHY-03-140Instrument *V3Wave vector, energy and temperature dependence of

the spin fluctuation dynamics in UAl2 Local Contact R ELechner, J Ollivier

Principal Proposer: E. Gratz, TU Vienna, Austria Date(s) of ExperimentExperimental Team: B.D. Rainford, Univ. Southampton, UK

N. Bernhoeft, CEA-Grenoble, FranceR.E. Lechner, HMI BerlinJ. Ollivier, HMI Berlin

*13-09-00 to 18-09-00

Date of Report: *19.2.2001

Introduction:UAl2 has long been held as an example of a ‘spinfluctuation’ system [1]. Most of its low temperature properties, such as the non-linear variationof the specific heat, T3lnT, and T2, have therefore been interpreted, at least in a qualitativesense, in the framework of paramagnon models for nearly ferromagnetic metals [2]. Thesetheories, based on the implicit formation of a narrow band of 5f like quasiparticles, focus attention onthe long wavelength fluctuations of the magnetisation density. Experimental confirmation ofsuch excitations is, to our knowledge, still lacking. Indeed, NMR studies of the 27Al nuclei [3] andprevious inelastic magnetic neutron scattering investigations[4-6] even suggest otherwise.We (attempted) to make a small angle Time of Flight scattering experiment to establish thenature of low frequency long wave length modes with the hope to integrate the data into our bulkmeasurements to build up a consistent theoretical picture in this compound which forms anatural link between the d-element (e.g. YCo2) and heavy fermion (e.g. UPt3) metals.

Experiment: A carefully prepared bole of UAl2 of pearshape with major section of approximate dimensions, 15 mm diameter and 10 mm height(prepared by Czochralski melting), was provided for these experiments. The sample was mounted on thecold finger of the orange cryostat in good thermal contact with the sample holder. The V3spectrometer was configured with the two-dimensionalposition-sensitive detector in the forward direction toinvestigate the long wavelength components of the spin fluctuation spectrum. A major problem occurred duringthis experiment (one of the first to try to exploit the useof the multi-detector in this small-angle configuration) : the design of the multi-detector in its present state(originating from conventional very-high-intensity'elastic' small-angle scattering experiments) appears tobe not yet sufficiently well adapted to this type ofinelastic scattering investigation, which intrinsicallyhas extremely low intensity. As a consequence, it hasnot been possible in this experiment to isolate the smallinelastic effects we had been looking for, from therelatively high background. As we were told by the instrument scientists, (who areworking on the solution of this technical problem) the

origin of these problems might be a combination ofseveral effects :a) The large divergence of the incident beam comingfrom a supermirror-coated guide, which - on the otherhand - is required in view of the low inelastic intensities,made it necessary to use a very large (30 cm*30 cm)beamstop placed directly in front of the multi-detector.This amounts to sacrificing the central part of thedetector.b) Even with this beamstop in place, residual small-anglescattering , probably from the walls of the cryostatseemed to overwhelm the inelastic signals (if there wereany).c) It is possible, that there is an additional contribution tothe background due to backscattering from materialbehind the detector. But this question still has to beexamined more closely.

Unfortunately this experimental problem prevented usfrom obtaining data in the desired region of (E,q) space and we were unable to address ourprimary goal. At large wave vectors we were able to confirm scattering measured at the ISIS institutepreviously.

References:1 AJ Arko et al., Phys. Rev. B8 414 (1973); RJ Trainoret al Phys. Rev. Lett. 34 1019 (1975)2 JR Schrieffer J Appl Phys 39 642 (1968); T Moryiaand A Kawabata J. Phys. Soc. Japan 34 639 (1973); GG Lonzarich and L Taillefer, J. Phys C18 4339(1985)3 S Takagi et al., J. Phys. Soc. Japan 60 1097 (1991)4 S Horn et al., J. Magn. Magn. Mat. 59 54 (1978)5 M Loewenhaupt et al., J; de Physique C4-40 142(1979)6 CK Loong et al., Physica 136B 413 (1986)File zu finden auf: (D500b/D/User/Gratz/ual2_rep.doc)

84

CHE-03-0164 // brandt // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° CHE-03-164Instrument NEATMagnetic Excitations in a mixed Mn(II,III)

tetrameric cluster Local Contact A. Desmedt

Principal Proposer: Hans-Ulrich Güdel, University of Bern, CH Date(s) of ExperimentExperimental Team: Grégory Chaboussant, University of Bern, CH

Reto Basler, University of Bern, CHStefan Ochsenbein, University of Bern, CH

30/04-10/05/2001

Date of report 20-09-01

The mixed valent tetrameric cluster[Mn4(OAc)2(pdmD)6](BF4)2 1 belongs to theclass of Single-Molecule Magnets showingslow relaxation of the direction ofmagnetization at low temperatures. The core of 1 consists of two MnIII and two MnII

ions, in a butterfly-like structure. Themanganese ions are connected via oxygenatoms from the ligand and via acetate bridges.Neglecting the influence of the acetate, acoupling scheme with two exchangeparameters Jbb and Jwb was proposed1 (Figure1).

Ĥex = -2·Jbb·(S2 – SA2 – SB

2) – 2·Jwb·(SA2 – S1

2 – S22)

Magnetic measurements could be bestunderstood with both interactions beingferromagnetic giving a ground state spin of 9.The ground state is zero-field split due to thesingle-ion anisotropy of the MnIII ions based onJahn-Teller elongation of one axis (O-Mn-N).

ĤZFS = D·[Sz2 - ·S(S+1)]

In order to obtain the D-parameter andparameters of possible higher order terms, theenergy difference between the MS-levels weremeasured with inelastic neutron scattering onNEAT with an incident neutron wavelength of 8Å. The INS-spectra at three differenttemperatures (2 K, 6 K and 12 K) are shown inFigure 2. We observed a prominent peak at0.45 meV, which is broader than theinstrumental resolution. Apart from that twowell resolved peaks at 0.345 meV and at 0.302meV came up as temperature is increased.From these results and from powder X-raydiffraction we had to conclude, that the sampleconsisted of more than one phase. One phaseleads to the broad feature at 0.45 meV and toan increased background at highertemperatures, whereas the other phase showssharp peaks, which belong to the transitions 8 7 and 7 6 (MS MS’). The cold transition9 8 is hidden beyond the broad peak. From

these data it was only possible to obtain the D-parameter: D = -0.023 meV.

Figure 1: Coupling scheme of the Mn4-butterfly

Figure 2: INS-spectra at three differenttemperatures. Only the neutron energy lossside is shown.References[1] Yae, J. et al, Inorg. Chem. 2000, 39, 3615-3623

85

EXPERIMENTAL REPORT

Eects of Fe Additions on the Helix

SpinStructure of the Metamagnetic Compound

MnAu2


Instrument V4

Local Contact

A. Hoell


2. 12. - 6. 12. 2001

Principal Proposer: Ulrich K. Roler, IFW Dresden

Experimental Team: A. Kreyig, IAPD, TU Dresden

U.K. Roler, IFW Dresden

A. Hoell, A. Heinemann, HMI Berlin


Neutron small-angle scattering provides a

well-suited tool to investigate compounds with

incommensurate spin-structures whenever their

periodicity is suÆciently long. Here, the sup-

pression of helimagnetism in MnAu2 induced

by Fe-substitution was investigated by SANS

on (Mn1xFex)Au2 being a companion exper-

iment to neutron diraction (see experimental

report PHY-04-867). From the classical work

of Herpin and Meriel on the parent compound

MnAu2, an appreciable SANS-signal from the

(000) magnetic satellite peaks was known to

occur. Measurements were done in the tem-

perature range T 2.5 K to 500 K (OF1)

for polycrystalline ribbons (Mn1xFex)Au2 (x =

0; 0:01; 0:02; 0:05; 0:075) (same samples as for

proposal PHY-04-867). A layer of about 5 rib-

bons (thickness 0.1-0.2 mm) was pressed be-

tween two Quartz-platelets (inner 15.5 mm,

1.3+1.1 mm thickness) as sample-holder. A rep-

resentative series of measurements done during

heating is shown in Fig. 1. There are indica-

tions of heli-modulated uctuations above TN

150 K, where the (000) satellite peak disap-

pears (see Fig. 1). The peak position is directly

related to the length of the helix-propagation

vector. However, above TN a magnetic SANS-

contribution possibly due to uctuations is still

preserved up to high temperature >400 K. A

careful search was made for helix spin-structure

in Mn0:925Fe0:075Au2 with negative result down

to T 2.5 K. The SANS results proving non-

existence or existence of helix spin-structure and

corresponding Neel-temperatures are in agree-

ment with wide-angle neutron diraction data,

magnetization and magnetoresistance measure-

ments. Collecting these data, we put for-

ward a tentative magnetic phase-diagram for Fe-

substituted MnAu2, as shown in Fig. 2.

0

100

200

300

400

500

600

700

800

0.5 0.75 1 1.25 1.5

Inte

nsiti

ty [C

ount

s]

q [nm-1]

T [K]

2.5

97.5

115

131

142

160

174

188

TN

(Mn0.95Fe0.05)Au2

Figure 1: Spherically averaged SANS-scans for

Mn0:95Fe0:05Au2 with increasing temperature.

The Neel-temperature TN is indicated.

0

100

200

300

400

0 1 2 3 4 5 6 7 8

T [K

]

x [at.% Fe substitution]

Helix

FM

TN TC

(Mn1-xFex)Au2

Figure 2: Conjectured x-T phase-diagram for

(Mn1xFex)Au2. transition temperatures

into helix spin-structure - multiple points for one

x from dierent experiments (SANS, E6, mag-

netic measurements) and/or samples, 4 Curie-

temperatures to ferromagnetic order from E6-

experiment PHY-04-867.

86


EXPERIMENTAL REPORT Proposal N° PHY-02-294Instrument E1Magnetic ordering in YMn2-single crystalline filmsLocal ContactJens Klenke

Principal Proposer: Wiebke Lohstroh, Oxford University Date(s) of ExperimentExperimental Team: Wiebke Lohstroh, Oxford University

1.5. – 7.5.01


The magnetic structure of single crystalline YMn2thin films was investigated using elastic neutronscattering. Bulk YMn2 samples show a first orderphase transition towards an antiferromagneticallyordered state below T~100K. However the Mn ionsare close to a magnetic - nonmagnetic instability andthe magnetic properties of YMn2 are stronglydependend on applied pressure of alloying (chemicalpressure). Elastic neutron scattering was used toinvestigate the static magnetic order of YMn2 in thinfilm geometry.The magnetic properties of single crystalline YMn2films have been investigated using elastic neutronscattering. The samples have been deposited onsapphire substrates and the [110] direction of the C15cubic lattice structure is parallel to the growthdirection. The d-spacing parallel to the surface isclose to the bulk values whereas the lattice isexpanded in the film plane. Neutron measurementsaround the nuclear and expected magnetic reflectionshave been done at various temperatures above andbelow the bulk ordering temperature T ~ 100K. Twodifferent crystallographic directions were accessible :[110] along the layer normal of the sample and [1 -11] direction in-plane. Fig 1 and 2 show the diffractedintensity in the vicinity of the crystal (110) and (220)reflections at 10k and at 150K.

Fig. 1: Scattered intensity around the (220) reflectionat 10K and 150K.

No magnetic reflections that correspond to an AFMordering ((110) and (201), respectively) could beobserved for temperatures above 10K.Simultaneously the nuclear reflections (220) and (1-11) have been measured and neither their intensitynor the momentum transfer Q was alteredsignificantly with temperature. In bulk samples thefirst order transition is accompanied by a large latticeexpansion of deltaV/V~5%. The thin film geometryclearly affects the magnetic ordering of YMn2. Eitherthe magnetic wavevector is different from the oneexpected from bulk samples and therefor notaccessible in the experiment or the clamping of thefilm to the substrate prevents the first order transitioncompletely.

2.22 2.24 2.26 2.28 2.30 2.32 2.34 2.36 2.38 2.40 2.42

0.05

0.10

0.15

0.20

0.25

0.30

T = 10K T = 150K

(2 2 0)

Inte

nsity

/100

MC

H [Å-1]

87


EXPERIMENTAL REPORT Proposal N° PHY-04-610Instrument V6Specular and diffuse neutron reflectivity of a

micropatterned Co antidot array Local Contact H. Fritzsche

Principal Proposer: Kristiaan Temst, K.U. Leuven Date(s) of ExperimentExperimental Team: Kristiaan Temst, K.U. Leuven

Johan Swerts, K.U. LeuvenHelmut Fritzsche, HMI Berlin

2-8 April 2001


With the recent advances in lithographytechniques, it has become possible to createvarious patterns in magnetic and super-conducting films. The general idea is that thispatterning (at micrometer scale or smaller) willaffect the physical properties by influencinge.g. superconducting flux pinning strength oraltering the magnetic anisotropy of the films.During the last few years, a lot of work hasbeen performed on small magnetic islands(‘dots’) in which the domain structure andmagnetization reversal have been studied.Much less work has been devoted to thecomplementary structure, namely holes(‘antidots’) in an otherwise continuousmagnetic film. In this project we have studied themagnetization reversal in a Co antidot film,which was prepared by combining electronbeam lithography, molecular beam epitaxy andlift-off techniques. A SiO2 substrate wascovered with resist ‘mushrooms’ in the electronbeam lithography facility at IMEC vzw, Leuven.This template was then covered with a Au(7.5nm)/Co(20 nm)/Au(7.5 nm) sandwich structureusing molecular beam epitaxy. After the lift-offprocedure, the antidots have a rectangularshape (dimensions 0.3 µm by 0.5 µm) andthey are placed in a square array with sideD=1.5 µm. The total patterned sample area isabout 25 mm².

Figure 1: AFM-micrograph of the antidot filmFigure 1 shows an atomic force microscopypicture of the completed sample. Quantitativemeasurements show that the surface

roughness of the antidot film is the same asthat of an unpatterned reference film.We have studied the magnetization reversal inthis antidot film by carrying out polarizedneutron reflectivity with spin analysis for 4different directions of the in-plane magneticfield with respect to the antidot lattice.Magnetization measurements using themagneto-optical Kerr effect had previouslyshown that, although the Co film ispolycrystalline and shows no crystallineanisotropy, a strong shape anisotropy isinduced by the antidot patterning, resulting intwo hard axes, one easy axis and one semi-easy axis. The PNR experiments allowed tomeasure the magnetization componentsparallel and perpendicular to the external fieldduring the magnetization reversal.

Figure 2: Specular reflectivity along hard axisFigure 2 shows the specular intensitymeasured along one of the hard axis, showingthe spin-flip and non-spin-flip intensities. Thesolid symbols indicate the sweep-up of themagnetic field, while the open symbols refer tothe sweep down. It is clear that in this case aspin-flip contribution can be observed, which isnot the case for magnetization along the easyaxis. This is due to domains which are pinnedby the corners of the antidots (as confirmed byMFM measurements).Micromagnetic simulations are performed inorder to compare the simulated domainstructures with the experimental PNR results.

0 50 100 150 200 250 3000

200

400

600

800

1000

1200

1400

1600B0319 Co antidots 90°

Spec

ular

inte

nsity

H (G)

I--

I-+

I+-

I++

02

46

8

2

4

6

8

2000Å

µm

88


EXPERIMENTAL REPORT Proposal N° PHY-04-611Instrument V6Neutron reflectivity of a dilute magnetic alloy filmLocal Contact H. Fritzche

Principal Proposer: Kristiaan Temst, K.U. Leuven Date(s) of ExperimentExperimental Team: K. Temst, C. Van Haesendonk, K.U. Leuven

J. Swerts, K.U. LeuvenH. Fritzsche, HMI Berlin

28 March – 2 April2001


In the beginning of the 1990’s, with theopportunities provided by submicrometerlithography, the study of dilute magneticsystems turned to samples whose dimensionsare comparable to the relevant microscopiclength scales. Up to now, the presence of sizeeffects in Kondo- and spin-glass alloys is acontroversial issue which requires additionalexperimental and theoretical efforts.Zawadowski et al. linked the size dependentKondo scattering to a surface-inducedanisotropy of the magnetic impurity spins. Thesurface-induced anisotropy should remainactive for more concentrated spin-glass alloys.This should lead to a particular magnetizationprofile in the dilute magnetic alloy films, whichwe intended to measure using polarizedneutron reflectivity.For this experiment Au-Fe spin-glass films(thickness 30 nm) were prepared by carefuldeposition in a MBE-system. High-purity Auand 57Fe were used and a nominalconcentration of 7 at. % Fe in the Au matrixwas achieved. Both Au and Fe wereevaporated from Knudsen effusion cells; assubstrates SiO2 wafers were used. Atomicforce microscopy and X-ray reflectivityexperiments indicated that these films havesmooth surfaces, with a typical root meansquare error of the order of 1 nm.

Figure 1: Polarized neutron reflectivity profile

Figure 1 shows the neutron reflectivity profileof a 30 nm AuFe film at 10 K and in a field of 6kG (the sample was field cooled). The dotsindicate the spin up and spin downreflectivities, while the solid line is a fit to thedata. A close observation of the data revealsthat there is a splitting between the spin upand spin down reflectivity, but its magnitude issmall due to the small net magnetization of thefilm. The solid line provides a good fit to thedata and the parameters are in goodagreement with the independently obtainedroughness values (from AFM and x-rayreflectivity data).

Figure 2: Spin asymmetry parameter

Figure 2 shows the spin asymmetry parametercalculated from the reflectivity data shown inFigure 1. The dots are the experimental data,while the solid line is the fit to the data. A goodfit can be made to the experimentally observedmagnetization in the film. The magnetizationwould even be more enhanced at still lowertemperatures, but this was experimentallyimpossible with the closed-cycle cooler.Analysis of the magnetization as function offield offered evidence for the existence of smallFe clusters (1 nm) in the Au matrix. Thisclearly demonstrates the potential of PNR forthe study of spin-glass films, which we willfurther exploit in future work.

0.00 0.02 0.04 0.061E-5

1E-4

1E-3

0.01

0.1

1

Fit parameters:Thickness: 28nmRoughness(AuFe): 1.5nmRoughness(SiO2): 0.2nmSdl(AuFe): 4.799E-06Sdl(SiO2): 3.7505E-06R(mag): 4.75e-8

R+

R-

R+-Fit R--Fit

Refle

ctiv

ity

q (1/Å)

0.00 0.01 0.02 0.03 0.04 0.05 0.06-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06AuFe 10K Field cooled (6kG)

R+ -R

- /R+ +R

-

q

89


EXPERIMENTAL REPORT Proposal N° PHY-04-0664Instrument V6Polarized Neutron Reflectivity analysis of thin films

with artificially induced magnetic roughnessLocal Contact Dr. H. Fritzsche

Principal Proposer: Dr. K. Temst (K.U. Leuven) Date(s) of ExperimentExperimental Team: J. Swerts (K.U. Leuven)

K. Temst (K.U. Leuven)H. Fritzsche (HMI Berlin)

26/11/01-6/12/01


Combining optical UV-lithography and molecularbeam epitaxy techniques, we have created patternedstructures on SiO2 substrates. A periodic structureof thin polycrystalline Ag lines (15nm thick, 2micron width) is grown on the substrate. In thisway, we create a patterned template that will beused as the substrate for the thin magneticFe(30nm) film. In Fig. 1 a schematic view of theprofile of the patterned Fe film is shown.

Fig. 1 Profile of patterned 30 nm Fe film.

The presence of the Ag lines, which have a muchlarger surface roughness than the rest of thesubstrate, will profoundly influence the magneticdomain structure and magnetic reversal process ofthe Fe film. The neutron reflectivity experiments were carriedout at room temperature and in ambient conditions.A magnetic field parallel to the film plane could beapplied using an electromagnet. We have studiedboth the specular and off-specular neutronreflectivity profiles and we have carried outpolarization analysis of the reflected neutrons.

Fig. 2 Intensity contour plot (up neutrons) in theqx-qz plane of the reciprocal space.

A reciprocal space map of the saturated patternedFe film is shown in Fig.2 as an intensity contourplot (up neutrons) in the qx-qz plane of thereciprocal space. The magnetic field was appliedalong the lines. Several satellite reflections can beobserved, corresponding to a lateral periodicity of15 micron, i.e. the periodicity of the underlyingarray of Ag lines. Magnetic field scans were performed for thespecular reflection and various satellite reflections.Fig. 3 reveals the intensity of the specular reflectionand the second order satellite reflection as functionof the applied field. The data reflect themagnetization reversal process in the Fe film.

Fig. 3 Specular intensity and 2nd order satelliteintensity as function of applied field.

According to the specular reflection, the reversalprocess is sharp and the saturation field is small.Fig. 3 clearly shows that the second order satellitereflection reveals additional information about themagnetization reversal process. The parts of the Fefilm that contribute mainly to the intensity of thesecond order satellite are the parts that are on top ofthe Ag lines. These parts clearly have a largersaturation field and the reversal process is lesssharp. Polarization analysis of the specularreflection as well as the off-specular reflectionsrevealed that the magnitazation reversal process isdominated by domain wall motion.

15 micron

Fe (30nm)

Ag (15nm) SiO2

0 2.10-4-2.10-4

0.02

0

0.04

qx

qz

0 20 40 60 80 100 120 140 160-0.20.00.20.40.60.81.01.2

Inte

nsity

(a.u

.)

Magnetic field (G)

2nd order R+

2nd order R-

Spec R+

Spec R-

90


EXPERIMENTAL REPORT Proposal N° PHY-O4-612Instrument V6Influence of magnetic domain wall shape and

size on polarised neutron reflectometry in“exchange bias” like sample

Local Contact Dr. H. Fritzsche

Principal Proposer: Mangin Stéphane, LPM Nancy Fr Date(s) of ExperimentExperimental Team: Mangin Stéphane, LPM Nancy Fr

Montaigne François, LPM Nancy FrFritzsche Helmut, HMI Berlin,De

14/03/01 – 22/03/01

Date of Report: 20/02/02Polarised Neutron Reflectometry (PNR) was usedto study domain wall (DW) in a ferrimagneticbilayer: GdFe/TbFe where GdFe is a soft magneticlayer and TbFe is a hard one. This bilayer belongsto materials known as exchange bias coupledsystem. Figure 1 present the hysteresis loopobtained at 12K on a GdFe(150nm)/TbFe(10 nm)cooled under 2kOe from 300K to insure a saturatedstate. the drop of magnetisation is attributed to thereversal of the GdFe layer while the TbFemagnetisation stay fixed. We assume that a DW isthen present at the interface in order to minimisethe exchange interaction. From thosemeasurements the DW thickness could beevaluated (Fig1 insert1)

-1

-0.5

0

0.5

1

-1000 -800 -600 -400 -200 0

Magnetic field H(Oe)

a)

b)

c)

0

100

200

300

400

500

600

-2000 -1500 -1000 -500 0

DW

thic

knes

s


(Å

)

I)

Figure 1: Magnetisation versus field at 12K onGd40Fe60(1500Å)/Tb55Fe45(100Å) after cooling thesample from 300K to 12K under a field of 2 kOe(+2kOe -2kOe +2kOe. Inset I: DW thicknessdeduced from magnetisation measurementsIt was clear, however that the determination of theactual magnetic profile was required. One of themore suitable technique to obtain it, is PNR. PNR measurements were performed for differentmagnetic applied fields at 12K in the samecondition than for the magnetisation measurements(fig1). the non-spin flip reflectivities R++ and R—andthe spin-flip reflectivities R+- and R-+ were collectedand analysed using a simulation program [4]. Fromthe simulation we could deduced the magneticprofile inside the bilayer (Figure 2) The DW sizeobtained from PNR measurements are in goodagreement with a micromagnetism calculation andmagnetisation measurements presented in Fig 1inset I. We then rotated the sample under anapplied field. The PNR measurements (Figure 3)permitted to observed DW of various angle. Wecould also evidence that for a field rotated by 200°an almost 200° DW was created whereas for field

larger than 220° the DW changed chirality to form a(360-220)° DW

0 200 400 600 800 10000

45

90

135

180

GdF

eTb

FeA

l

HM

= 2000 Oe, = 0° H

M= 100 Oe, = 180°

HM= 500 Oe, = 180° HM= 1000 Oe, = 180° H

M= 2000 Oe, = 180°

angl

e °

(deg

rees

)Thickness t(Å)

Figure 2: Magnetic depth profile configuration for variousmagnetic states provided by plotting the angle (t)between magnetisation and the applied magnetic field asa function of the thickness of the sample.

1 0- 5

1 0 - 4

1 0- 3

1 0- 2

1 0- 1

1 00 a )

HM

= 3 0 0 O e = 9 0 °

R+ +

R- -

R+ -

1 0- 5

1 0- 4

1 0- 3

1 0- 2

1 0- 1

1 00 b )

HM

= 3 0 0 O e = 1 6 0 °

Neu

tron

ref

lect

ivity

0 2 x 1 0- 2

4 x 1 0- 2

6 x 1 0- 2

1 0- 5

1 0- 4

1 0- 3

1 0- 2

1 0- 1

1 00

q ( Å- 1

)

c )H M = 3 0 0 O e = 2 0 0 °

Figure 3: PNR data intensity on GdFe/TbFe at 12Kunder HM= 300 Oe for angle a) 90°, b) 160°, c) 200°.

R+- , R++ and R— reflectivities (symbols) are presentedwith the fit (lines)

References:[1] S. Mangin, G. Marchal, B. Barbara, Phys. Rev.Lett. 82, 4336 (1999)[2] S. Mangin, C. Bellouard, H. Fritzsche, Physica B276-278, 558 (2000)[3] S. Mangin, C. Bellouard, F. Canet, C. ChatelainH. Fritzsche, submitted to Phys. Rev. B[4] Software pnrsim developped by U. Englisch forBENSC

91


EXPERIMENTAL REPORT Proposal N° PHY-04-665Instrument V6Magnetic profile in Gd40Fe60/TbXFe1-X exchange

coupled bilayers studied by polarised neutronreflectometry Local Contact

Dr. H. Fritzsche

Principal Proposer: Mangin Stéphane, LPM Nancy Fr Date(s) of ExperimentExperimental Team: Mangin Stéphane, LPM Nancy Fr

Montaigne François, LPM Nancy FrFritzsche Helmut, HMI Berlin, De

29/10/01-5/11/01


We used Polarised neutron reflectometry (PNR) tostudy the magnetic configurations in exchangecoupled Ferri/Ferrimagnetic amorphous bilayersystems: Gd40Fe60/TbXFe1-X [1]. For the two rareearth-transition metal alloys the moment held by Feis antiparallel to the one held by the rare earth. Themagnetisation of Gd40Fe60 is along the rare earthmoment. For TbXFe1-X the magnetisation is parallel(resp antiparallel) if X > Xcomp (resp: < Xcomp). For X= Xcomp the magnetisation of the alloy is zero, whichmakes it very similar to an antiferromagnet. As theexchange coupling between the two layer isdominated by the Fe-Fe coupling at the interface, ifX > Xcomp (resp: < Xcomp) the coupling the two alloymagnetisations is ferromagnetic (resp:antiferromagnetic. For X=Xcomp the sign of thecoupling depend on the sample historyWe have already performed PNR measurementson Gd40Fe60/Tb45Fe55 (X>Xcomp) which showed anegative exchange bias behaviour. It permitted toevidence the formation of a domain wall DW at theinterface as the GdFe magnetisation was drag bythe applied field while the TbFe magnetisationstayed fix [1,2,3]The PNR measurements performed onGd40Fe60/Tb12Fe88 (X<Xcomp) are shown in figure2. Magnetisation versus field measured at 300K arepresented in figure 1: it shows three magnetisationsteps

-200 -150 -100 -50 0 50 100 150 200

c) b) a)

Nor

mal

ized

Mag

netis

atio

n


Figure 1: Magnetisation versus field at 300K onGd40Fe60(1000Å)/Tb12Fe88(500Å) (+2kOe -2kOe

+2kOe).PNR measurements performed for differentmagnetic field (at different positions of thehysteresis loop) are shown in figure 1. The non-spinflip reflectivities R++ and R—and the spin-flipreflectivities R+- and R-+ were collected andanalysed using a simulation program [4]. It

permitted to conclude that the first magnetisationdrop is due to the reversal of the TbFemagnetisation , the second to the reversal of the allbilayer, and the third one to the reversal of theTbFe toward the field. We could even deduced thatbefore the TbFe reverses a DW is created at theinterface. Simulations are still being performed todefine the DW location and shape.

0,01 0,02 0,03 0,04 0,05 0,061E-4

1E-3

0,01

0,1

1

q (A-1)

R-- (H= 5 kOe)

R-- (H= 150 Oe)

R++ (H= 30 Oe)

1E-4

1E-3

0,01

0,1

1

Neu

tron

Ref

lect

ivity

R++ (H= 5 kOe)

R++ (H= 150 Oe)

R-- (H= 30 Oe)

Figure 2: PNR data intensity at 300K on

Gd40Fe60(1000Å)/Tb12Fe88(500Å) R+- , R++ and R—

reflectivities

For X = Xcomp, magnetisation measurementsshowed a shift of the hysteresis loop toward anegative field which is the signature of an exchangebias behaviour. PNR measurements showed thepresence of DW at the interface of the two layerReferences:[1] S. Mangin, G. Marchal, B. Barbara, Phys. Rev.Lett. 82, 4336 (1999)[2] S. Mangin, C. Bellouard, H. Fritzsche, Physica B276-278, 558 (2000)[3] S. Mangin, C. Bellouard, F. Canet, C. ChatelainH. Fritzsche, submitted to Phys. Rev. B[4] Software pnrsim developped by U. Englisch forBENSC

92

EXPERIMENTAL REPORT

Determination of the magnetic reversal of

(110)-oriented Fe-layers

Proposal NEF

Instrument V6

Local Contact

J. Hauschild


04.07.01 - 08.07.01

Principal Proposer: H. Fritzsche, J. Hauschild, HMI Berlin

Experimental Team: J. Hauschild, HMI Berlin

H. Fritzsche, HMI Berlin


In this report we present the continuation of

an investigation concerning the nature of the

magnetic reversal of (110)-oriented Fe layers [1].

The determination of the magnetic structure of

the chromium layers revealed a phase transi-

tion from an commensurate spin density wave

(C-SDW) to a low temperature incommensurate

spin density wave (I-SDW). The amount of the

CSDW phase decreases from 250 K and is no

longer detectable at 175 K [2].

0 50 100 150 200 250 3000.0

1.0x10-3

2.0x10-3

3.0x10-3

4.0x10-3

5.0x10-3

6.0x10-3

7.0x10-3

8.0x10-3

9.0x10-3

1.0x10-2

χ =

dS/

dH

T (K)

Figure 1: Susceptibility measured in the vicin-

ity of HC as a function of temperature.

Our multilayer V(110)/[1.2 nm Fe / 26 nm

Cr]15/1.2 nm Fe/10 nm Cr was measured on the

V6 mounted on the closed cycle cooler. The

re ectivities R for parallel/antiparallel align-

ment of magnetization and neutron spin were

recorded parallel to the spin- ip channels R.

The asymmetry S = R++R

R+++Ris proportional to

the magnetization parallel to the magnetic eld.

Fig. 1 shows the susceptibility in the vicin-

ity of the coercive eld as a function of temper-

ature. One observes two plateaus at low and at

high temperature, respectivly, with a transition

between T1 = 150 K and T2 = 225 K. This tem-

perature range coincides with the phase transi-

tion from I-SDW to C-SDW [2].

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

asym

met

ry S

µ0H (Oe)

T = 10 K T = 125 K T = 150 K T = 200 K T = 10 K

Figure 2: Hysteresis of the iron layers at dierent

temperatures.

In order to check whether the principle of

the magnetic reversal is aected, we investigated

the hysteresis at several temperatures below and

above the phase transition (Fig. 2). For all

shown measurements the spin- ip channels were

recorded but did not show any signal besides the

background. This excludes the coherent rota-

tion of the iron magnetization. The reversal is

achieved by domain wall movement. The ques-

tion why the susceptibility of the Fe layers is

able to determine the phase transition in the Cr

and not the coercivity HC itself needs further

eorts to answer.

[1] H. Fritzsche, J. Hauschild, S. Bonn, Y. Liu,

BENSC Report 2000, p. 74.

[2] H. Fritzsche, J. Hauschild, H. A. Graf,

A. Hoser, H. Maletta, BENSC Report 1998,

p. 91.

93


EXPERIMENTAL REPORT Proposal N° EFInstrument V6Polarized Neutron Reflectometry of a Pt/Co

bilayer Local Contact J. Hauschild

Principal Proposer: H. Maletta, D. Schmitz, HMI Date(s) of ExperimentExperimental Team: D. Schmitz, HMI

J. Hauschild, HMI 19.-25.06.2001


In magneto-optical recording materials are ofinterest which exhibit high storage densityachieved by perpendicular magneticanisotropy. The Pt/Co system is a suitablecandidate due to the advantages of adjustablehysteresis characteristics, stability againstcorrosion and increased Kerr rotation in theblue laser regime. In this context the interfaceproperties are of special interest because theystrongly influence the overall magneticproperties of the layer system. Therefore weintended to determine the magnetization depthprofile at a single Pt/Co interface with twodifferent methods, Polarized NeutronReflectometry (PNR) and X-Ray ResonantMagnetic Scattering (XRMS).

Before the PNR experiment the reflectancecurves were calculated in order to checkwhether PNR is sensitive enough. In thecalculation layer thicknesses and interlayerroughnesses from Cu K measurements wereused (Pt (6.2 nm) / Co (2.6 nm) / Cu (2.5 nm) /Ta (4.3 nm) / Si). Furthermore it was assumedthat 2 atomic Pt layers at the interface to Coare ferromagnetic with a magnetic moment of0.5 µB per atom. The result is shown in thefigure (green line) and compared with theresult for non-magnetic Pt (black line). Thedifference between the two models is verysmall.

Nevertheless, PNR measurements wereperformed at V6 in order to check thesimulation. The result of the measurement isalso shown in the figure (dots). Unfortunatelythe measurements confirm that PNR is notsensitive enough to determine themagnetization depth profile. In contrast,element-specific XRMS measurementsperformed in the hard X-ray range at theDeutsches Elektronen-Synchrotron (DESY)revealed the magnetization depth profile of Ptat a single interface to Co. The XRMS resultswere published in reference [Gei01].

0,00 0,02 0,04 0,06 0,08 0,101E-4

1E-3

0,01

0,1

1

refle

ctan

cemomentum transfer / A-1

0,00 0,02 0,04 0,06 0,08 0,101E-5

1E-4

1E-3

0,01

0,1

1

refle

ctan

ce

momentum transfer / A-1

0,00 0,02 0,04 0,06 0,08 0,10-1,2-1,0-0,8-0,6-0,4-0,20,00,20,40,60,8

asym

met

ry

momentum transfer / A-1

Fig.: Calculated (lines) and measured (dots)PNR curves and the correspondingasymmetry. Two cases were calculated, Ptnon-magnetic (black line) and Pt ferromagneticat the interface to Co (green line).

[Gei01] J. Geissler, E. Goering, M. Justen, F. Weigand,G. Schütz, J. Langer, D. Schmitz, H. Maletta, R.Mattheis, Phys. Rev. B 65, 020405(R) (2001)

94


0. 01 0. 02 0.03 0.04

0.00 1

0.0 1

0 .1

1

- 1

C

Q ( A )

Ref

lect

ivity

0 .001

0 .01

0 .1

1B

0 .000 1

0.00 1

0.0 1

0 .1

1 A

- - ++ S F Fi t

EXPERIMENTAL REPORT Proposal N° EFInstrument V6Asymmetric magnetization reversal in a

Co/CoO exchange bias multilayer Local Contact H. Fritzsche

Principal Proposer: M. Gierlings, M. Gruyters, D. Riegel, HMIBerlin Date(s) of Experiment

Experimental Team: M. Gierlings, H. Fritzsche, M. Gruyters, HMIM. J. Prandolini, FU-Berlin Jan 2001

Jul / Aug 2001


It is of technological importance and of greatscientific interest to be able to understand andto investigate magnetization reversalprocesses in magnetic thin films. Exchangebias (EB) systems, i.e. ferromagnetic materialscoupled to an antiferromagnet have been ofspecial interest to many research groups sincethe discovery of the EB effect. In the EB state[1], characterised by an unidirectional shift

-2000 -10 00 0 10 00 2000

-0.008

-0.004

0.000

0.004

0.008

E

T= 10 K

C

B

A

H

Mag

netic

Mom

ent (

emu)

H (Oe)

of the magnetic hysteresis loop and byincreasing coercivities with decreasingtemperatures, one finds very good conditionsto observe new phenomena such asasymmetric reversal processes on oppositesides of the hysteresis loop; as has been foundin different EB systems [2].Besides conventional magnetometry such asSQUID, polarized neutron reflectometry (PNR)is well suited to study reversal processes.Measuring the NSF intensities of up-neutrons,R++ and down neutrons, R- -, PNR can be usedas a classical magnetometer. By measuringthe SF intensities R+ - and R- +, one canadditionally exploit the unique property ofneutrons, that their spin is flipped if themagnetization in the sample has an in-planecomponent perpendicular to the spinquantization axis.The present investigations were performed ona [Co/CoO/Au]20 EB multilayer at 10 K, i.e.

after field cooling the sample in a field of+4000 Oe to induce EB (left figure).

A drastic change of magnetization reversalprocesses in [Co/CoO/Au]20 multilayers hasbeen found by PNR (right figure). In theexchange bias state (T=10 K), rotation is themain mechanism only for increasing fieldsrelated with a significantly increased SF signal(point C). For the decreasing field branchwhich is in the direction opposite to the bias(cooling field), the mechanism changes todomain wall motion (point B). In the latter casethe SF signal is only slightly altered. Furtherinvestigations on the sample have beenperformed with a position sensitive detector toget information about diffuse scattering onmagnetic structures as a function of the field.The data analysis is still in progress. [1] W. H. Meiklejohn and C. B. Bean,

Phys. Rev. 105, 904 (1957).[2] M. R. Fitzsimmons et al.,

Phys. Rev. Lett. 84, 3986 (2000).

95


EXPERIMENTAL REPORT Proposal N° EF

Instrument E1, E2Phase transformations in Cu2-SeLocal Contact

Principal Proposer: S. Danilkin Date(s) of ExperimentExperimental Team: S. Danilkin, D. Hohlwein, R. Schneider, HMI

A. Skomorokhov, IPPE, Obninsk, RussiaN. Bickulova, SGPI, Sterlitamak, Russia

14th-25th May 2001

Date of Report: 22.01.02 *

Copper selenide Cu2-Se belongs to a mixedionic-electronic superconductors with a broad range ofhomogeneity (0<<0.25). Temperature of the superionictransition is about 403K for Cu2Se and decreases withdeviation from stoichiometry. Superionic -phase existsat room temperature in the composition range between=0.150.25 and has phase transformations to low-temperature phase at 250-180 K [1]. In -Cu2Seselenium atoms form the fcc lattice and Cu cations aredistributed over the intersites. At present, however, thereis no general opinion on the structural transformations,which occur during the phase transitions [2, 3]. Theeffects of doping of copper selenide by other elementshave not been investigated also.

In the present measurements we studiedstructure of Cu2-Se and Li0.25Cu1.75Se with triple-axis E1spectrometer and Cu1.8Se single crystal with E2 flat-conediffractometer. Neutron diffraction of powder samplesCu1.75Se, Cu1.98Se and Li0.25Cu1.75Se was measured withE1 spectrometer. The measurements were done at roomtemperature with 2.439 Å incident neutrons wavelength.The 40’ collimation was used. The diffraction pattern ofCu1.75Se was indexed to fcc structure with latticeparameter 5.749 Å. The structure of Cu1.98Se wasclassified into monoclinic system with parameters a =7.11, b = 12.44, c = 7.1324 Å and = 90.26, 107.94,89.82. Doping of the copper selenide by lithiumleaded to formation of the monoclinic structure withparameters: a = 7.35, b = 12.44, c = 6.97 Å and =90.14, 107.66, 91.11.

The single crystal Cu1.8Se was studied with E2diffractometer at temperature range of 150300 K. Thesample had cubic structure with a = 5.833 Å and wasabout 1 cm3 in size. The measurements were done atincident wavelength of 1.21 Å. The crystal was alignedwith [011] direction normal to scattering plane.Reciprocal (hk0) layers were measured during cooling atT=300, 250, 200, 190, 180 and 150 K and, then, atheating at T=200, 230 and 300 K. Splitting of (022)reflection and appearance of new weak satellite spotswas detected at 200 K during cooling. The strong diffusescattering observed at room temperatures decreasesnoticeably with the increasing temperature. Theobserved diffuse scattering comes probably from thelattice defects. In -Cu1.8Se at room temperature coppervacancies are distributed statistically in the crystal. Theobserved superstructure in the low-temperature phaseand decreasing of the diffuse background withtemperature shows that the copper vacancies are orderedbelow 250-200K.

Fig. 1. The Intensity distribution of Cu1.8Se inthe (hk0) reciprocal layer at 300 250 and 150 K.

References

1. T. Ohtani, Y. Tachibana, J. Ogura, T. Miyake,Y. Okada, Y. Yokota, J. Alloys and Compounds 279(1998) 136.2. Z. Vucic, O. Milat, V. Horvatic, and Z. Ogorelec,Phys. Rew. B 24 (1981) 5398.3. Y. Okada, T. Ohtany, Y. Yokota, Y. Tachibana andK. Morishige, J. Electr. Microscopy 49 (2000) 25.

96



Instrument E2Localization of fluorine and hydrogen atoms inthe (NH4)2KGaF6 elpasolite Local Contact

D.Hohlwein

Principal Proposer: A.D.Vasiliev Date(s) of ExperimentExperimental Team: D.Hohlwein, BENSC, Univ. Tübingen

M.L.Afanasiev

M.V.Gorev

I.N.Flerov

Institute of Physics RAS, Krasnoyarsk, Russia

11.12.01–15.12.01


Crystals of elpasolite and cryolite families withcommon formula A+

2B+M3+F6 (A+ B+ in cryolites)

are cubic in a high temperature phase and belong tothe wide class of ordered perovskites with sp.gr.

m3Fm (Z=4). Many of them undergo phasetransitions on cooling. Lattice distortions associatedwith a phase transition are often considered to bedriven by one of two extreme mechanisms, namely:the order-disorder type or the displacive type. Themain question remaining is to know whatmechanism dominates in each particular case. In accordance with the model of structural phasetransitions in ammonium cryolites (NH4)3B3+F6,suggested on the ground of NMR and calorimetricdata, structure distortions are due to the orientionalordering of (NH4)+ in 4b site and (B3+F6)– ions.Replacement of NH4

+ ion in this site by potassiumion transforms cryolite structure into elpasolite one.

The (NH4)2KGaF6 compound was prepared bysynthesis from solution. Solute of Ga(OH)3 inconcentrated HF acid was evaporated till saturation.This saturated solution was added with equimolarmixture 2NH4+KHF2+Ga(OH)3 with HF as solvent.Solution resulted was kept at 70C till crystallizationbeginning and then was cooled with the rate of 0.5K/hour till room temperature. As the result, crystalswith the volume about 0.5mm3 were obtained. The (NH4)2KGaF6 compound undergoes threesuccessive phase transitions: cubic–tetragonal–monoclinicI–monoclinicII at 288, 249 and 244 Kapproximately. According to calorimetric data onlythe phase transition at T2=249K may be connectedwith some order-disorder processes. The main aims of the investigation are:

a) to determine the actual positions of protonsand fluorines in cubic and distorted phases;

b) to refine on this basis the model ofstructural phase transitions in ammoniumcryolites and elpasolites.

Neutron powder patterns of (NH4)2KGaF6 werecollected at four temperatures: 298, 270, 247 and150K with wavelength 1.21Å. Now the patterns areunder investigation using Rietveld refinement.

Fig.1 Neutron powder patterns at 298, 270, 247 and 150K (from top to bottom).

97


EXPERIMENTAL REPORT Proposal N° PHY-01-970 PHY-01-969Instrument E5“The determination of the disorder of the ammonium ions

in the phase II of trirubidium hydrogen disulfate-triammonium hydrogen disulfate”

Local Contact Dr.A.Loose

Principal Proposer: L . S . S m i r n o v , S U C S S C R F I T E P ,M o s c o w , R u s s i a


Experimental Team: V . S a r i n , I N R R A S , M o s c o w , R u s s i a 30.04-20.05.2001K.Wozniak, University of Warsaw, Warsaw, PolandP.Dominiak, University of Warsaw, Warsaw, Poland


There is interest to determine the type ofammonium groups reorientation in phases II of[Rbx(NH4)1-x]3H(SO4)2 (or TRAHS): about crystaland molecular axis or only about molecular thatfor the understanding of phase diagram of thesemixed crystals. The x-T phase diagram of TRAHSwas studied in [1] by dielectric spectroscopymethod. It was shown that a substitution of 10%of NH4 by Rb is enough to stabilize the phase IIfrom room temperature to low temperature, wherebelow ca. 30 K an orientational glass phase isobserved. Indeed the phase II in TRAHS (x=0.18)was observed with the help of neutron powderdiffraction from 290 to 11 K [2].

Recent neutron single crystal study ofTRAHS with x=0.11 is carried out on E5 fourcircle diffractometer at RT using =0.8902 Å.The number of measured Bragg reflections is2392 and number of reflections used for LSMcrystal structure determination by XTAL andShelx-93 programs is 2010 for which rejectioncriterion is 3.0 sigma. Space group is C2/c, Z=4with lattice parameters a=15.2610 Å, b=5.8027Å, c=10.0652 Å and =101.81 degree.Determined atomic positions are presented inTable 1 and bond lengths and angles arepresented in Table 2. It is interest to carry out the comparison ofFourier maps for ammonium groups NH4(1)and NH4(2) obtained by x-ray and neutrondiffraction. X-ray Fourier maps present chargedensity distribution and neutron Fourier mapspresent nuclear density distribution near N(1)and N(2) below and above of monocliniceplane (010). These maps are presented in Figs.1(a-h). Fourier maps of nuclear densitydistribution of hydrogen in H3H4H1tetrahedron face of NH4(1) and in H5H5aH6tetrahedron face of NH4(2) are presented inFigs. 2(a,b). Nuclear density distribution ofhydrogen atoms are smeared strongly for

account of temperature factors at T=290 K inaccordance with presented in Table 1. The H(7)acid hydrogen is disordered (Table 1) and thiscould be seen in Fig. 3.

Table 1. Atomic positions in[Rb0.11(NH4)0.89]3H(SO4)2 at RT.

Atom x y z U(eq)S 0.1142(4) 0.2177(9) 0.4627(6) 20(1)

O(1) 0.0145(2) 0.1846(8) 0.4424(5) 37(1)O(2) 0.1503(3) 0.2231(8) 0.6058(4) 39(1)O(3) 0.1289(3) 0.4328(7) 0.3981(5) 41(1)O(4) 0.1490(3) 0.0273(7) 0.3982(5) 40(1)N(1) 0.3012(2) 0.7757(4) 0.3471(2) 32(1)Rb(1) 0.3012(2) 0.7757(4) 0.3471(2) 32(1)N(2) 0.5000 0.2305(5) 0.2500 28(1)Rb(2) 0.5000 0.2305(5) 0.2500 28(1)H(1) 0.3277(15) 0.8970(40) 0.4050(30) 127(9)H(2) 0.2380(10) 0.8190(40) 0.3330(30) 117(8)H(3) 0.3198(15) 0.7860(40) 0.2630(16) 112(7)H(4) 0.3108(11) 0.6260(30) 0.3870(20) 98(6)H(5) 0.4589(18) 0.3140(60) 0.2760(40) 178(17)H(6) 0.4651(11) 0.1290(30) 0.1816(17) 93(5)H(7) -0.0043(14) 0.0400(40) 0.0130(20) 45(5)

The R1/wR2 factors are 0.121/0.255.Table 2. Bond lengths and angles in[Rb0.11(NH4)0.89]3H(SO4)2 at RT.

Bonds, Å Angles, degree

S-O(1) 1.5199(47) O(1)-S-O(2) 107.23(33)S-O(2) 1.4227(46) O(1)-S-O3) 106.90(28)S-O(3) 1.4407(49) O(1)-SO(4) 107.04(28)S-O(4) 1.4332(50) O(2)-S-O(3) 111.91(30)

O(2)-S-O(4) 112.07(30)O(3)-S-O(4) 111.34(34)

N(1)-H(2) 0.9884(87) H(2)-N(1)-H(7) 98.49(1.08)N(1)-H(7) 0.8614(142) H(2)-N(1)-H(2) 106.37(77)N(1)-H(2) 0.9884(87) H(2)-N(1)-H(7) 115.05(1.29)N(1)-H(7) 0.8614(142) H(7)-N(1)-H(2) 115.05(1.29)

H(7)-N(1)-H(7) 103.10(1.43)H(2)-N(1)-H(7) 98.49(1.08)

N(2)-H(3) 0.9570(92) H(3)-N(2)-H(4) 112.43(1.03)N(2)-H(4) 0.9387(104) H(3)-N(2)-H(5) 110.16(86)N(2)-H(5) 0.9663(77) H(3)-N(2)-H(6) 112.90(97)N(2)-H(6) 0.9350(122) H(4)-N(2)-H(5) 104.51(1.06)

H(4)-N(2)-H(6) 111.23(1.11)H(5)-N(2)-H(6) 105.01(1.01)

98


Fig. 1(a). X-ray for NH4(1)_010_-0.45

Fig. 1(c). X-ray for NH4(1)_010_0.45

Fig. 1(e). X-ray for N(2)_010_-0.30

Fig. 1(g). X-ray for NH4(2)_010_0.30

Fig. 2(a). The H3H4H1 face for NH4(1) group.

Fig. 3. Fourier map of (SO4)-H-(SO4) dimmer

Fig. 1(b). Neutron for NH4(1)_010_-0.45

Fig. 1(d). Neutron for NH4(1)_010_0.45

Fig. 1(f). Neutron for NH4(2)_010_-0.30

Fig. 1(h). Neutron for NH4(2)-010-0.30

Fig. 2(b). The H5H5aH6 face for NH4(2) group.

It is necessary to continue the study of crystalstructure of TKAHS at low temperature for thelocalization of hydrogen positions ofammonium groups.References:1. A.I.Baranov, V.V.Dolbinina, E.D.Yakushkin et

al., Ferroelectrics, 217 (1998) 285.2. L.S.Smirnov, A.I.Baranov, I.Natkaniec et al.,

FTT, 43 (2001) 117.

N(I)Rb

99


EXPERIMENTAL REPORT Proposal N° CHE-01-971Instrument E5Investigation of the Phase Transition in a

(NH4)[H5(PO4)2] single crystal Local Contact A. Loose

Principal Proposer: S. Troyanov, Moscow State University Date(s) of ExperimentExperimental Team: E. Kemnitz, Humboldt-Universität Berlin

A. Loose, HMI BerlinM. Reehuis, Univ. Augsburg

22.05.-27.05.2001+11.06.-26.06.2001


The phase transition in (NH4)[H5(PO4)2] at180 – 210 K has been investigated recent-ly by single crystal X-ray diffraction [1].One acid hydrogen atom and the NH4group, which are disordered in the roomtemperature modification, become orderedafter this phase transition below 180 K.Therefore a neutron diffraction study wasrequired to localize the protons moreprecisely in both modifications.

The neutron diffraction experimentswere carried out at the BER II researchreactor. A single crystal of (NH4)[H5(PO4)2]with the dimensions of 6.0 x 2.5 x 2.5 mm3

has been investigated on the four circlediffractometer (E5) using a copper mono-chromator (220 Cu, = 0.8902 Å). Thedata were collected at room temperatureand at 80 K with a two-dimensional(90 x 90 mm2) position sensitive 3He-detector. The data at low temperatureswere influenced by overlapping withaccidental diffraction from the Al container.

At RT, 1323 reflections werecollected, 1261 of which were indepen-dent. The unit cell dimensions from X-raystudies [2] were refined using 200 centeredreflections: a = 10.156(4) Å, b =7.554(3) Å,c = 9.507(4) Å, = 100.71(4)°, Z = 4,space group C2/c. The structure wasrefined anisotropically for all non-hydrogenatoms and for three acid protons bound tothe phosphate group. The ammoniumgroup was found to be disordered aroundan inversion center over ten protonpositions with occupancies 0.33 – 0.50.The refinement with 1088 reflections and96 parameters converged at wR2 = 0.2899and R1 = 0.1373 (SHELXL-93).

In contrast to the results of the X-rayinvestigation [1], the acid proton waslocalized on a two-fold axis resulting in a

symmetrical hydrogen bond O3···H3···O3´,with O···H distance 1.207(5) Å andOHO = 177.5°. These discrepancies withthe results of the X-ray study are due tothe KKM effect. Similar differences havebeen found earlier for the crystal structuresof K4(HSeO4)3(H2PO4) [2] andNa5H3(SeO4)4 [3].

The data of the measurement at80 K (1935 collected and 1917independent reflections) showed atransformation to the following primitivecell: a = 10.040(4) Å, b = 7.628(2) Å,c = 9.558(3) Å, ß = 102.51(4)°, Z = 4,space group P21/c. The final refinement(isotropic only for the four protons of NH4)with 1608 reflections and 182 parametersconverged at wR2 = 0.2878 andR1 = 0.1275. The former symmetricalhydrogen bond became unsymmetrical:O4-H3···O8 with O4-H = 1.06(1) Å, H3···O8= 1.37(1) Å and OHO = 177.4(9)°.

Apparently, an ordering of theammonium group upon cooling and theformation of the N-H···O hydrogen bonds isa driving force for unsymmetrical changesin the O···H···O bond between two H2PO4groups.

[1] S. Troyanov, E. Snigireva, E. Kemnitz,Z. Kristallogr. 215 (2000) 364.[2] S. Troyanov, I. Morozov, M. Reehuis, E.Kemnitz, Z. Kristallogr. 215 (2000) 377.[3] S. Troyanov, M. Zakharov, M. Reehuis,E. Kemnitz, Kristallografiya 47 (2002) No.1 (in press).

100

GEO-01-1041 // brandt // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° GEO-01-1041Instrument E5High temperature structure of mercalliteLocal Contact Dr. A. Loose

Principal Proposer: Dr. Karsten Knorr, Universität Kiel Date(s) of ExperimentExperimental Team: Gisela Lentz, Universität Kiel

29.10.-18.11.2001


KHSO4 belongs to a family of compounds, in whichthe NH4, Rb and Cs-members undergo a phasetransition to a superprotonic state in the region of410 to 475 K. But for KHS04 Sharon and Kalia(1977) found no hint for a superprotonic state.There is obviously a change of critical parametersleading to the superprotonic conductivity from K toNH4 resp. Rb we are currently investigating.

The crystals were obtained from an aqueoussolution of K2SO4 and H2SO4 resp. D2SO4 at a ratioof 1:2 through slow evaporation. Large clearcrystals up to 1.5 cm in diameter (2mm for KDSO4)crystalized at 323 K within a few days. Thesubstance is slightly hygroscopic and was carefullydried at 393 K before each measurement andcovered with silicon oil or the glue used in theexperiment.DSC measurements of KHSO4 andKDSO4 were performed and three phase transitionsabove RT were found with a small shift towardslower temperatures for KDSO4: an exothermic,irreversible at 407.5 K (392 K) with very smallstructural changes, an endothermic at 456 K (449K) with a large volume effect and a smallendothermic effect on the shoulder of the meltingpeak at 475 K (469.5 K). The melting point wefound to be at 481.5 K (474.5 K). Abdel-Kader et.al. (1994) found as well the phase transition at ca.453 K, but not the one at 407.5 K. Instead of this,he found an exothermic effect at ca. 363 K.

Two structural models for the RT-structure ofKHSO4 were proposed earlier, both with the spacegroup Pbca by Cotton et al. (1975) and by Payanand Haser (1976). The latter found two differentpositions for one of the proton sites. Both proposedmodels are layered structures of HSO4— -dimers,K-ions and H-SO4— -chains.

To check this we performed single-crystal x-raystructure analysis of the room temperature phase.In several single crystal data sets we obtainedadditional reflexions which lead us to the spacegroups P212121 and P2111 supported through themorphology of the crystals, which is 222. Bothphases are probably metastable with respect to the“ideal” structure Pbca at the phase transition at407.5 K.As a preceding test of the neutron experiment weundertook a single-crystal x-ray structure analysis

of a deuterated crystal, which led us to the spacegroup P2111 as well.

To gain more information about the proton positionsand their rôle in the first phase transition weplanned to obtain two datasets on the E5 4-circlediffractometer with a deuterated crystal: one at RTand one at 423K.

After testing several crystals it turned out, thatproblems with the determination of the orientationmatrix were related to a mechanical instability ofthe furnace. Therefore, only a dataset at ambientconditions was collected in the remaining time. Thedata were collected at λ = 0.890 Ǻ with a two-dimensional position sensitive 3He-detector.

The dataset at RT confirmed the spacegroup P2111with the polar axis parallel the hydrogen bonds.There were far more reflexions observed breakingthe symmetry of Pbca than in the X-ray datasets.This supports our hypothesis, that the protons aremainly responsible for the lowering of symmetry.The proton positions were clearly found. Therefinement supports the work of Cotton et al.(1975). He found an assymmetric hydrogen bondwith only one proton site per bond. There was nohint for a symmetric hydrogen bond like inK3H(SO4)2 (Noda et al. (1992)). The deuterationwas determined to be 58% through the refinementof the occupation factor for protons and deuterons.Unfortunately, the dataset had no sufficient qualityto calculate the anisotropic thermal parameters ofthe protons resp. deuterons.

References:Abdel-Kader, M.M., El-Shawarby, A., Housny, W.M., El-Tanahy, Z.H., El-Kabbany, F. (1994). Mater.Res.Bull. 29,317-25Cotton, A., Frenz, B.A., Hunter, D.L. (1975). Acta Cryst.B31, 302-4Noda, Y. Kasatani, H. Watanabe, Y. Terauchi, H. (1992).J.Phys.Soc.Jap. 61(3), 905-15Payan, F., Haser, R.(1976). Acta Cryst. B32, 1875-9Sharon, M., Kalia, A.K. (1977). J.Chem.Phys. 66, 3051-5

101


EXPERIMENTAL REPORT Proposal N° CHE-01-990

Instrument E9Metal nitridesLocal Contact M. Tovar, D. Többens

Principal Proposers: G. Auffermann, R. Kniep, MPI CPfS Dresden Date(s) of ExperimentOther Applicants: Yu. Prots, R. Niewa, MPI CPfS DresdenExperimental Team: G. Auffermann, Yu. Prots, MPI CPfS Dresden

M. Tovar, HMI Berlin22.05. – 28.05.01


The nitrido compounds Ca3MN (M = Tl, Ge, Sn, Pb, P,As, Sb, Bi) are reported to crystallize in the perovskitestructure type or distorted variants thereof [1]. Only thegroup 15 compounds can be described following theoctett rule (Ca2+)3(M3-)(N3-) and are found to be coloredinsulating compounds or semiconductors. In thecorresponding group 13 and 14 compounds the maingroup elements suffers from the lower electron count performular unit. Thus, the compounds exhibit metallicproperties.

This led us to investigate the corresponding rare earth(RE) compounds RE3MN, which also do not follow thesimple octett rule, starting with M = In. Since thesamples were prepared by ceramic methods from thebinaries REN and RE2In only microcrystalline powdersamples were obtained.

X - ray investigations on powdered samples reveal theatomic arrangement of the metal atoms, whereas wefailed in the precise determination of the cerium andindium order and the nitrogen occupation factor. There-fore we have carried out neutron diffraction experiments.

Neutron diffraction experiments were carried out on thephase Ce3InNz [2]. These studies at room temperatureled to the complete structure determination. The profilerefinement (see Fig. 1) of the collected data revealed thecerium and indium order and the nitrogen occupation

Fig. 1: Neutron diffraction diagram of Ce3InN at roomtemperature (wave length 1.7965 Å). The observed,calculated and difference profiles are shown. The ticksmark the positions of the Bragg reflections. Profilerefinements were carried out with the programFULLPROF [3]. factor (Ce3InN0.90(1)) and additionally confirmed theresults of the chemical analysis (Ce3InN0.91(2)O0.05(1)) con-

cerning the nitrogen content as well as the X-rayinvestigations.

The crystal structure of the room temperature modifica-tion can be described in the perovskite structure type:Pmm, a = 5.0432(1) Å (see Fig. 2) [2].

Fig. 2: Crystal structure of Ce3InN0.9 at roomtemperature (Ce: red, In: violet, N: green).

Magnetic susceptibility measurements [4] carried out inthe temperature range from 1.4 to 400 K revealedmagnetic ordering between the cerium atoms below 9.5and 6 K. A neutron diffraction experiment carried out onCe3InN0.9 at 2 K showed that additional strongreflections do exist which only can be explained by aspin structure in which there is an antiferromagneticordering. The determination of the spin structure ofCe3InN0.9 (I-centered cell: a = 10.0758(7) Å) is still inprogress.

References

[1] R. Niewa, F. R. Wagner, W. Schnelle, Z. anorg. allg.Chem. 2001, 627, 365 and references given therein. [2] M. Kirchner, part of diploma thesis, FSU Jena, 2002.[3] J. Rodriguez-Carvajal, Laboratoire Léon Brillouin,Fullprof.2k, Version 1.9c, 2001.[4] R. Niewa, M. Kirchner, private communication.

102

OTH-01-0993 // brandt // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° OTH-01-993

Instrument E9Cation migration in alkali-saturatedmontmorillonites Local Contact

D. Többens

Principal Proposer: A. Moukarika, University of Ioannina, Greece Date(s) of ExperimentExperimental Team: A. Lappas, FORTH, Greece

D. Gournis, University of Ioannina, GreeceD. Többens, HMI, Germamy

18-06-01 till 26-06-01

Date of Report: 23-01-02

The clay mineral montmorillonite, a member ofthe dioctahedral smectite group, is widely used as araw material due to its powerful catalytic andsorbent properties. Montmorillonite is consisting ofa regular stacks of negatively chargedaluminosilicate layers separated by charge-balancing cations and water in the so-calledinterlayer region. To a greater or lesser degree thesematerials have the natural ability to adsorb andexchange cations from solutions and it is this cation“storage” that makes them such an importantcomponent in industrial applications. A strikingfeature though of montmorillonite clays is that uponsaturation with small cations, such as Li+, andheating at 200-300°C, the negative layer charge isreduced which drives the system to lose itsimportant natural ability to expand (swelling) theinterlayer space during hydration or variouschemical reactions. This phenomenon wastentatively attributed to the migration of the Li+

cations from the interlayer space to vacant latticeoctahedral sites, where the cations are trapped andsimultaneously provide local charge compensation.Other researchers proposed a different migrationbased on the location of Li+ cations at the bottom ofthe hexagonal cavities of the basal oxygen surfaces.

The present experiment was directed towards astudy of the structural properties of montmorillonitesaturated with lithium or caesium cations and thepurpose was: (i) to refine the crystal structure ofmontmorillonite which consists even today an openproblem in the field of clay mineralogy and (ii) toinvestigate the possible steps in the migration of thecations exchanged in the interlammelar space andin particular to determine the actual sites wherethese cations can effectively reside. Morespecifically we performed neutron diffractionmeasurements on four samples: Li- and Cs-saturated montmorillonites before and after heat-treated at 300oC. Patterns were collected at roomand at liquid Helium temperature (10 K). We alsoperformed measurments on a Li-montmorillonitesample, not thermally treated but with the interlayerwater removed by a distillation method. Diffractionprofiles were measured at various temperaturesbetween ambient and 300 oC in steps of 80 oC in

order to follow the changes that occur in thestructure due to the migration of Li through thecrystal lattice.

Neutron difraction patterns of Li- (a) and Cs- (b)montmorillonite samples air-dried and heat-treatedat 300 oC are shown in Fig. 1. Heat-treatment of Li-clay sample causes a few variations in thecorresponding diffraction pattern while the patternof Cs-clay remains almost unaffected. The majorchange in the diffraction pattern of Li-montmorillonite is the development of newreflections at 2Θ= 56.5o and 34o. These new linesmay indicate a different location of Li ions incomparison with Cs ions in the crystal structure andmay result to a different space group in the case ofLi. A complete refinement of the crystal structureof these samples will allow us to determine theactual sites in the clay layers where these cationscan effectively reside.

5 10 15 20 25 30 35 40 45 50 55 60

Q-223

QQQ00

5

113Q

003/

Q11

0

002

001

(b)Cs-mont-300

(a) Li-mont-300

Li-mont-ad

2 Θ

Cs-mont-ad

Q-22300

5040/

Q

Q13

0Q/1

12

-111

/Q11

0/02

0

002

001

Q-223

040/

QQQ00

5

113Q00

3/Q

110/

020

002

001

Fig. 1. Neutron-diffraction patterns of Li- (a) and Cs- (b)montmorillonite samples air-dried and heat-treated at

300 oC. (Q: stands for quartz)

d=3.15Åd=1.90Å

103



Instrument E9Study of the metal order in the solid solution serie 2ZnS -CuInS2

Local Contact M. Tovar

Principal Proposer: S. Schorr, Universität Leipzig, IMKM Date(s) of ExperimentExperimental Team: S. Schorr, Universität Leipzig, IMKM

M. Tovar, HMI Berlin 6. 7. - 12. 7. 2001


Physical and chemical properties of materials areoften controlled by substitutions and non-stoichiometries. Thus solid solution seriesespecially including phase transitions are stronglyrecommended for reflecting dependencies ofchemical composition, element ordering andmicrostructures as well as stability parameters astemperature and pressure. We are dealing withstructure-property-correlations by means ofsemiconducting mixed crystals e.g. used asphotovoltaic materials. Therefore we study thesystem Zn2xCu(1-x)In(1-x)S2 (ZCIS) which was foundto form an approximately complete solution seriesand a phase transition from the cubic sphaleritetype to the tetragonal chalcopyrite type at x~0.2[1]. The electronic band gap decreasesexponentially from 3,6 eV for ZnS to 1.9 eV atx~0.1 to reach the gap value of the end memberCuInS2 (1,5eV) even in the phase transition region[2]. This behavior is suggested to correlate withdifferent metal contents and ordering.Conventional and synchrotron radiation methodsfailed due to the electronic similarity of Zn and Cuand because of the chalcopyrite space groupparities used respectively. Also EXAFS studies [5]were not significant. Since neutron radiation helpsto overcome these problems neutron powderdiffraction experiments have to be used firstlydone on those materials by us. Samples were synthesized by solid state reactionof the elements (4N) in sealed evacuated silicatubes at T=850°C. The homogeneity of thepowders were checked by X-ray diffraction,optical microscopy and microprobe. Neutronpowder diffraction experiments were carried outfor samples near ZnS and near the phase transitioncomposition as well as in the tetragonal region ofZn2xCu(1-x)In(1-x)S2. We used the high resolutionpowder diffractometer E9 (=1.7973Å) at theBerlin Neutron Scattering Center (Hahn-Meitner-Institut Berlin, Germany). Data refinements weredone by the FULLPROF program[4]. For therefinement of the tetragonal structures differentoccupation models for the metals on the twotetrahedral sites were used. The refined latticeparameters are in good agreement with the resultspreviously obtained by X-ray diffraction [1].Hereby the lattice parameter ratios c/a>2 are

caused by the small deviations of the S atoms fromits ideal position [3]. In contrary to the X-ray dataa nonlinear correlation with composition wasfound. The lattice parameters and sulfur positionsare independent from the occupation model of themetals. But site occupancy and displacementfactors vary with the different models, for whichthe R-values are used as a first significance check.From 0.0>x>0.1 the model with statisticdistribution of Zn on Cu- and In-site fits best. Withdecreasing tetragonality the distribution modelslose significance. Thus from 0.0>x>0.2 the anti-site occupation of Cu and In is increasing. In thecubic region the displacement factor of thestatistically occupied metal site decreases for0.2<x<0.9 to be constant for 0.9<x<1.0. The latterregion with its strong decrease of the optical gapmay be due to doping properties, whereas the otherregions are due to substitution effects.

Fig. 1: R-values of the refinement of the tetragonalstructure region using different occupation models.

[1] K. Bente, T. Döring, Chem. Erde 51 (1991) 291[2] I. Luck et al. Cryst. Res. Technol. 31 (1996) 841[3] A. Zunger, Appl. Phys. Lett. 50 (1987) 164[4] FULLROF 2000, LLB, Paris, France[5] I. Luck, PhD-Thesis, Universität Leipzig, 1996

0 20 40 60 80 1006,0

6,1

6,2

6,3

6,4

6,5

6,6

6,7Zn0.05(CuIn)0.95S

R-B

ragg

Zn on Cu-site (0,0,0) [%]

0 20 40 60 80 1006,7

6,8

6,9

7,0

7,1

7,2

7,3

7,4Zn0.1(CuIn)0.9S

R-B

ragg


0 20 40 60 80 1007,8

7,9

8,0

8,1

8,2

8,3

8,4

8,5

Zn0.15(CuIn)0.85S

R-B

ragg


0 20 40 60 80 1006,6

6,7

6,8

6,9

7,0

7,1

7,2

7,3Zn0.2(CuIn)0.8S

R-Br

agg


104


EXPERIMENTAL REPORT ProposalEIGENFORSCHUNGInstrument E9CRYSTAL CHEMICAL STUDIES IN THE SPINEL

SYSTEM CUCR2O4-NICR2O4 Local Contact M. Tovar

Principal Proposer: M. Tovar, HMI Berlin Date(s) of ExperimentExperimental Team: C. Welker, Universität Stuttgart 02.03.-03.03. 2001

27.08.-01.09. 2001 16.11.-18.11. 2001


Experiment:

Due to the Jahn-Teller effect many transition metalcompounds show a more or less strong deviationfrom their ideal crystal structure. Examples can befound in the spinel and the perovskite family forinstance [1]. Depending on the configuration of thed-shell electrons, the Jahn-Teller effect causeslocal polyhedral or a macroscopic crystal structuredistortion by reducing the symmetry of the wholestructure.

The compounds CuCr2O4 and NiCr2O4 crystallize atroom temperature in a tetragonally distorted spinelstructure with c/a < 1 and c/a > 1, respectively [2-4].

Since this compounds exhibit a contrary distortionone could expect that by mixing both a not-distortedcubic state could be reached. However, in the solidsolution series Cu1-xNixCr2O4 within 0.825< x < 0.88surprisingly phases with orthorhombic symmetrywere found [3].

On basis of this observation aims of the projectwere todetermine the distortion of the CuO4/NiO4-

tetrehedra in the solid solution series asfunction of composition

- determine the structural parameters of theorthorhombic phase and

- characterize its behavior as a function oftemperature.

Room temperature powder diffraction measure-ments were carried out for samples Cu1-xNixCr2O4with x = 0, 0.2, 0.4, 0.6, 0.85 and 1. Temperaturedependent measurements were performed forsample x=0.85 at temperatures between 2K and500K in different temperature intervals. Forstructure refinement the Rietveld method was used.

Results:

For all samples besides x=0.85 at roomtemperature tetragonal symmetry was found. Thesymmetry of the sample with x=0.85 depends on itsthermal history: on heating it shows orthorhombic,on cooling tetragonal symmetry. The individualtetrahedral distortion overcrosses at x 0.9 (fig. 1).

Fig. 1: Tetrahedral distortion in the solid solution series CuCr2O4-NiCr2O4

Between 2K and 400K Cu0.15Ni0.85Cr2O4 shows twocrystallographic and one magnetic phase transition.Lattice parameters as a function of temperaturewere determined by whole powder pattern fitting(fig. 2)

Fig. 2: Lattice parameters of Cu0.15Ni0.85Cr2O4 as function oftemperature

The solution of the yet unknown orthorhombic andmagnetic structure of Cu0.15Ni0.85Cr2O4 is inprogress.

Literature:

[1] Dunitz, J.D., Orgel, L.E. (1957): Electronic properties oftransition-metal oxides - I. - J. Phys. Chem. Solids 3, 20-29.

[2] Dollase, W.A., O´Neill, H.St.C. (1997): The spinels CuCr2O4and CuRh2O4. - Acta Cryst. C53, 657-659.

[3] Dulac, J. (1969): Spinelles déformés dans le système rhoditede nickel et de cuivre. - Bull. Soc. fr. Minéral. Cristallogr. 92,25-29.

[4] Tovar, M. (2000): Dissertation, Universität Heidelberg

100

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125

100

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110

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(4×)

(2×)

angle O-T-O

CuCr2O4 NiCr2O4

0 100 200 300 400 500

8.00

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8.20

8.30

8.40

8.50

8.60

8.00

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8.20

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8.50

8.60

Temperature [K]

a, b, c [Å]

orthorhombictetragonal

cubic

a, c

c

a

b

a

105


EXPERIMENTAL REPORT Proposal N° PHY-03-169Instrument V5-SPANNi-Diffusion in NiGa with NSELocal Contact Pappas C.

Principal Proposer: Kaisermayr M., Univ. Wien Date(s) of ExperimentExperimental Team: Pappas C., BENSC

Vogl G., HMI/Univ. WienTriolo A., BENSC

20.3.-1.4.2001


Probing jump diffusion in crystalline solidswith neutron spin-echo spectroscopy

M. Kaisermayr, C. Pappas, B. Sepiol andG. VoglPhys. Rev. Lett. 87, 175901 (2001).

Neutron spin-echo spectroscopy has beenapplied to jump diffusion in a crystalline solid.Definite advantages of spin-echo spectroscopyover quasielastic neutron scattering are thedirect visual discrimination of fast and slowdiffusion processes and the high resolution inthe time-energy domain. The potential of themethod is demonstrated by way of Ni diffusionin the intermetallic alloy NiGa.

Time correlation as measured on the Ni52.5Ga47.5 singlecrystal at 1100°C and 2 = 130°. The line representsS(Q,t) as calculated on the basis of NN-jumps. S(Q,t) isthe sum of two exponentials represented by the dashedlines. The first exponential corresponds to shortresidence times on anti-sites (Ga-sublattice), while thesecond exponential is associated to long residence timeson the regular sites (Ni-sublattice).

Time correlation as measured on the Ni52.5Ga47.5 singlecrystal at 1130°C. The two spectra were obtained in asimultaneous measurement at 2 = 94° (top) and 2 =130° (bottom). The lines represent the time correlation ascalculated for nearest-neighbor jumps (solid line) andnext nearest neighbor jumps (dashed line). Inset: B2-unit cell. A Ni atom may perform a NN-jump intoa vacancy on a Ga-site (solid arrow) or a NNN-jump intoa vacancy on the Ni-sublattice (dashed arrow).

106

PHY-02-0284-LT // brandt // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N°PHY-02-284LT

Instrument E1Crystal electric field-lattice interactionLocal ContactH.A.Graf

Principal Proposer: E. Gratz, Inst. Experimentalphysik; TU Wien Date(s) of ExperimentExperimental Team: A. Hoser, RWTH-Aachen

K. Hense, Inst. Experimentalphysik; TU WienC. Anzur, Inst. Experimentalphysik; TU Wien

26.3.2001-6.4.2001


ProposalThe idea of this proposal ‘crystal electric field-lattice interaction’ was to investigate theinteraction of the phonons and the crystal-electric-field (CEF) in the cubic Laves phaseNdAl2. For this we proposed to measure the q– dependence and the temperature-variation ofthe optical phonon branch centered at13.5meV (at the -point) and the adjacent CEFlevel known to exist at 11meV. Fromtheoretical point of view this phonon-CEF-interaction in NdAl2 should be most significantfor these two species of interactions.If this interaction is measurable at all weexpected:i) a temperature dependent shift mainly

of this ‘13.5meV–phonon–branch’ dueto the temperature induced occupationof the 11meV-CEF-level,

ii) a dispersion (q-dependence) of theCEF-level owing to this coupling to thedispersive phonons.

Unfortunately the experiments in the scope ofthe given beam time do not allow to come to a

unique decision because of the followingreasons:i) there were problems with the

monochromator crystal at the begin, sowe lost about two days of beam-time.

ii) because of the relatively low flux on theE1 spectrometer unexpected long scan– times were needed.

In the remaining measuring time we mainlyperformed scans at 170K of the ‘13.5meV–phonon–branch’ and the ‘11meV-CEF-level’ inthe (,0,0)-direction from q = (0,0,0) up to q = (0.8,0,0). For completeness we alsomeasured the two acoustic phonon branchesin (,0,0) – direction. These results aredepicted in the figure below. The inset shows aconstant q-scan of the CEF-excitation atq = (0.2,0,0). These data would be suitable toanswer our questions, however in that casefurther measurements at additionaltemperatures (lower and higher than 170K) arenecessary.

const. q-scan at q=(0,2;0;0)

E [meV]10 11 12

coun

ts

0

100

200

300

400

T = 170 K

0 1

E [m

eV]

0

2

4

6

8

10

12

14

16

107


EXPERIMENTAL REPORT Proposal N° 02-306Instrument E1Crystal electric field-lattice interactionLocal Contact H.A.Graf

Principal Proposer: E. Gratz, Inst. Experimentalphysik; TU Wien Date(s) of ExperimentExperimental Team: A. Hoser; RWTH-Aachen

K. Hense, Inst. Experimentalphysik; TU WienC. Anzur, Inst. Experimentalphysik; TU Wien

06.8.2001-18.8.2001


In our recent proposal we asked for beamtimein order to study the crystal electric field -phonon interaction and additionally, to find outwhether also the magnons (below the Curietemperature) are influenced by the phonons inthe cubic NdAl2 Laves phase. For this purposea beamtime of 12 days was given(PHY020306). However the low flux on the E1spectrometer and the small NdAl2 singlecrystal size (about 0.4cm3) showed us, that itwas rather hopeless to solve the mentionedproblems in a reasonable time. We therefordecided to study the same phenomena (crystalfield – phonon interaction) using our NdCu2single crystal which is much larger in size andwhere we had good reasons that such aninteraction must be measurable. In the figurebelow the temperature variation of twocharacteristic phonons (Q = 0,4.4,0) belongingto the same

phonon branches (with the Ag - symmetry) inNdCu2 and in YCu2 are presented. (YCu2 isconsidered as a nonmagnetic isostructuralreference compound). As can be seen, there isa remarkable shift with increasing temperatureof the NdCu2 – phonon (and of the Ag- phononbranch), whereas the shift of thecorresponding YCu2 – phonon is much lesssignificant. (The lattice dynamics of YCu2 hasbeen studied recently by us and is submitted toPhys Rev. B). Since from symmetry argumentsit follows that this Ag – phonon-branch cancouple to the E = 7.2meV crystal fieldexcitation of NdCu2 , we can be sure about theexistence of this phenomena. In a preliminaryanalysis we tried to fit these data to models.The lines are the result of the fitFigure: Temperature variation of the(Q=0,4.4,0)-phonon measured for NdCu2 (left)and YCu2 (right). The lines are the results of fitprocedures.

108

PHY-02-0295 // Eamonn Beirne // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT

CEF excitations in single crystal PrNiSn

Proposal N° PHY-02-295Instrument V2Local Contact Klaus Habicht

Principal Proposer: K A McEwen, University College London, UK Date(s) of ExperimentExperimental Team: Eamonn Beirne, UCL 19/03/01-30/03/01

Keith McEwen, UCLKlaus Habicht, HMI

Date of Report: September 2001

The RNiSn (R=rare earth) series of intermetalliccompounds show a diverse range of properties. PrNiSnand NdNiSn have not been studied to a large extent andno previous neutron studies have been published. Likethe other RNiSn compounds, PrNiSn has the TiNiSi(space group Pnma) crystal structure, with the Pr ion onthe Ti site. Our recent magnetic susceptibilty results on singlecrystal PrNiSn show no magnetic ordering down to 2K,but do demonstrate strong anisotropy at lowtemperatures. b has a clear maximum around 12K andminimum around 4K, with the upturn below 4K alsoevident in c. We attribute the anisotropy andtemperature dependence to crystalline field effects on thePr ion. From data taken on polycrystalline PrNiSn onHET at ISIS, several crystal field peaks are evident.There is clear evidence of magnetic excitations around 2,3.5, 5.1 and 7.5 meV, with four more excitationsappearing using a higher incident energy of up to30meV.The aim of the experiment on V2 was to investigate theselow lying modes on our single crystal. For the majorityof the experiment, the collimators were set to 40’-60’-60’with a fixed kf=1.55Å-1 and a Be filter behind the sample,giving us an incident energy of 5meV. The sample wasmounted with the a* and c* in the horizontal plane. The results of the experiment are diverse and exciting. At6K the low lying excitations are clearly seen in the [001]direction, with an additional low lying peak at 0.5meV.This is particularly exciting, as it appears to confirm thecrystal field parameters and energy levels predicted bythe fitting program FOCUS used on the HET data. In the[100] direction, the 3.5meV peak has shifted to3.75meV, while the 2.4meV peak is not visible. Thissuggests that the 0.6 and 3.5meV modes are polarisedalong b*, while the 2.4meV mode is polarised along a*.At 2K the high energy peaks are visible, but a broadasymmetric peak appears at lower energy [Figure 1]. It isespecially interesting to note that as we go further alongc*, this broad peak shifts to a higher energy andincreases in intensity. At all temperatures and high Q, thehigh energy peaks do not get swamped by this broadfeature and are always evident.Following the 2.4 and 3.5 meV peaks as we move along(001) to (003), we determined that the 3.5 peak splitsinto two peaks, with the largest splitting at the (002). The2.4meV peak appears to have no dispersion over thisrange. Carrying out the same study along the a* direction, the3.75meV peak again splits into 2, but merges back at the

(2,0.0) and at a lower energy of 3.45meV.

0 1 2 3 40.0

1.0x10-4

2.0x10-4

3.0x10-4

4.0x10-4

5.0x10-4

6.0x10-4PrNiSn (0,0,1) 2K

6K

coun

ts/m

onito

r

E (meV)

Figure 1: Temperature dependence of the (0,0,1), clearly showing thebroad asymmetric anomolous peak at 2K at low energy.

2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.40.0

4.0x10-5

8.0x10-5

1.2x10-4

1.6x10-4

2.0x10-4

2.4x10-4

2.8x10-4

(0,0,1) (0,0,1.5) (0,0,2)

coun

ts/m

onito

r

E (meV)

Figure 2: Splitting of the E=3.5meV along the c* direction. (0,0,1.5)a& (0,0,2) have been ofset by 1.5E-4 and 2E-4 respectively.

The dispersion of the two modes around 3.5 meV hasbeen deduced and fitted to that for exchange coupledcrystal field excitations. Details are given in a paperpresented at ICNS 2001 [1].

We also confirmed that there is no magnetic orderingdown to 2K: no additional superlattice peaks were seenin scans along [001] and [100].

[1] E D Beirne, K A McEwen, K Habicht and D Fort,to be published in Applied Physics A

109


EXPERIMENTAL REPORT Proposal N° EF-SF1Instrument V2-NRSEQ- andTemperature Dependence of Phonon Linewidths in Single

Crystal Pb Measured with Neutron Resonance Spin Echo (NRSE)Local Contact K.Habicht

Principal Proposer: T.Keller, B.Keimer MPI f. FKF, StuttgartK.Habicht, R.Golub, F.Mezei, HMI, Berlin Date(s) of Experiment

Experimental Team: T.Keller, MPI für Festkörperforschung, StuttgartK.Habicht, TU-Darmstadt

14.05.– 27.05.2001;08.11.– 18.11.2001;27.11.– 29.11.2001


The investigation of phonon lifetimes was subjectof the experimental study carried out with the coldtriple axis spectrometer V2 (FLEX) which has beencombined with the neutron resonance spin echo(NRSE). The NRSE option provides the resolutionnecessary for lifetime determination of elementaryexcitations. Furthermore due to its precisely definedprecession field regions the NRSE techniqueenables the application of the ‘phonon focussingtechnique‘ required for lifetime measurements ondispersive excitations.

The TAS was operated with fixed ki=1.7 -1 in aconfiguration giving a transverse q-resolution ofabout 0.01 -1 FWHM. A tunable PG filter wasused to eliminate second order contamination. The field tilt angles have been calculated fromBorn-von-Kàrmàn fits to dispersion data from theliterature, typical tilt angles were 30° and=+25° for [00]phonons with <0.2 r.l.u.Cylindrical crystals with [100] and [110] axesperpendicular to the scattering plane were used.Amplitudes of spin echo curves have beenmeasured as a function of spin echo time . Withinstatistical error the decay was consistent with asingle exponential decay P()=P0 exp(-), i.e.Lorentzian lineshape when Fourier transformed. [00] TA phonons shown a significant q-dependence in the range 0.05<<0.02 r.l.u. Atwavenumbers = 0.1, 0.15 r.l.u. a change inlifetime with temperature (5K<T<300K) isexperimentally found (see fig.1).

We can summarize the experimental results asfollows: Extrapolated linearly to zero temperaturethe energy width remains finite. At T<10K theelectron-phonon interaction is expected to dominateover the phonon-phonon interaction. No lifetimechange at the superconducting transition was found.The lifetime does not change significantly forwavenumbers < 0.5 r.l.u.

The spin echo signal dependence on tilt angle

and frequency has been measured at the [0.1 0 0]TA phonon at T=150 K and is found to be asmoothly varying function with detuning. Thefrequency detuning curve is shown in fig.2. These findings indicate that resolution issues otherthan detuning of instrumental parameters areinvolved. Therefore curvature of the dispersionsurface, sample mosaic and instrumental resolutionare currently investigated by Monte-Carlo methodsas well as analytically.

Fig.1: Q- and temperature dependence of phononlinewidths in Pb. represents the HWHM of theLorentzians.

Fig.2: Detuning of frequency, arrow indicates calculatedfrequency maximum, Gaussian (solid line) and sin(x)/x(dashed line) fits correspond to 2/2=8x10-3

0 50 100 150 200 250 3000

10

20

30

40

[

eV]

T [K]

[2 0.15 0] [2 0.10 0] [2 0.05 0]

0 100 200 300 400 500 6000.00

0.05

0.10

0.15

0.20

0.25

0.30

P

eff2

111


EXPERIMENTAL REPORT Proposal N° CHE-03-146Instrument V3Proton diffusion in lanthanide(III) doped zeolite Y,

a contrast agent for medical imaging Local Contact R.E. Lechner

Principal Proposer: D.H.Powell, University of Durham, GB Date(s) of ExperimentExperimental Team: M. Gay-Duchosal, University of Lausanne, CH

J. Ollivier, HMIJ. Pieper, HMI

6/9/00-13/9/00


AimsThe aim of these expertiments was toinvestigate the rotational and translationaldiffusion of water in Ln3+ exchanged zeolite Y(referred to henceforth as Ln-Y). Zeolite Y is asynthetic faujasite with ~ 13 Å supercagesconnected by a network of smaller cages. Ln3+

will exchange from solution with thoseintrazeolite Na+ ions that are located in thesupercages and, unless the zeolite isdehydrated, the Ln3+ ions are thought to remainas aquaions in the supercages. Gd-Y has beenproposed as a paramagnetic contrast agent formagnetic resonance imaging of thegastrointestinal tract. The exchange of watermolecules between the Gd3+ hydration shelland unbound pore water, and the diffusion ofthe pore water, are expected to play animportant role in the contrast enhancementmechanism. Our 17O and 1H NMR resultsindicate that the water exchange process maybe diffusion limited at ambient temperature.We therefore wished to obtain information onthe water diffusion in hydrated Ln-Y, and howit may be different to that in hydrated Na-Y.Since gadolinium is a strong neutron aborberwe chose to study La-Y and Tb-Y to have anion close in radius to Gd3+ and to investigatethe effect of ionic radius.

ExperimentsWe made measurements on five samplesTb-Y, hydrated and vacuum driedLa-Y, hydrated and vacuum driedNa-Y, hydratedThe hydrated samples all contained ca. 26%H2O by weight.We made QINS measurements at two differentnominal energy resolutions (100 eV and 34eV) and at two temperatures (~ 285 K and320 K) at the higher resolution.

ResultsThe results show broadening that appears to bedue only to rotational diffusion of the waterprotons indicating that, as suggested by ourNMR measurements, the translational diffusionof the intrazeolitic water is slow. We seesignificant differences in the rotationalbroadening of the water for the three differentexchangeable cations. We will be able tocharacterise the rotational diffusion process anddetermine the rotational diffusion coefficient andestimate the activation energy for the process inthe three systems. We will at least be able toobtain an upper limit of the translationaldiffusion coefficient and determine whether thisis consistent with the model we use to interpretour NMR data. The full analysis of this data hasbeen delayed by the departure of one of the teammembers (MGD) from his position. We expectto complete analysis and submit the data forpublication in 2002.

112

EXPERIMENTAL REPORT

Anion Reorientation in Sodium Phosphate/Sodium SulfateSolid Solutions

Proposal N MAT-03-157

Instrument V3

Local Contact

R.E. Lechner


Jan 29 – Feb. 5, 2001Principal Proposer: D. Wilmer, University of MunsterExperimental Team: H. Feldmann, University of Munster

D. Wilmer, University of Munster

Date of Report January 29, 2002

Coherent quasielastic neutron scattering experi-ments have been performed on solid solutions ofNa2SO4 and Na3PO4 in order to examine the re-orientational anion motion in the picosecond range.Like pure Na3PO4, xNa2SO4 · (1− x)Na3PO4 be-longs to a group of materials which exhibit both dy-namic anion rotational disorder and good cation con-duction in a cubic phase. Advantages of adding sul-fate are the stabilisation of the ion-conducting cubicphase down to room temperature and an increasedion conductivity due to the creation of vacancies.

Spectra fromxNa2SO4 · (1− x)Na3PO4 with x =0.1 andx = 0.5 were taken at several temperaturesusing an incident wavelength of 5.1A and an elasticresolution of about 100µeV. They are well fitted bya sum of aδ function and a single Lorentzian (repre-senting the quasielastic scattering), both broadenedby the Gaussian instrumental resolution function.

As clearly seen in Fig. 1, the anion rotational dy-namics is faster upon increasing the sulfate content.Parallel to the findings for the ionic conductivity,the activation energy falls with increasingx, yield-ing values of 0.074 eV and 0.052 eV forx = 0.1 and0.5, respectively.

The obtained data were further analysed on the ba-sis of theQ-dependent quasielastic intensity. In theaccessibleQ range, the intensity of the quasielasticcontribution rises monotonically withQ, see Fig. 2.While the shape of theQ-dependent intensity doesnot vary between samples of different composition,the intensity is found to be proportional to(1− x),und thus to the concentration of phosphate anions.

Comparing the predictions of different models(model A: isotropic anion rotational diffusion; modelB: rotational diffusion on a circle with only threeoxygen atoms involved) for the coherent quasielasticscattering of individual rotating units with the exper-imental results gives a clear indication that the ob-served motion is performed by three oxygen atomswhich rotate on a circle, while the fourth oxygenatom, at least on the time scale defined by the exper-iment, remains fixed. The rotating units in modelsA and B are not the tetrahedral anions alone but in-clude a sodium cation attached to it. This approachexplains, for the first time, the additional quasielas-

tic intensity at lowQ, i.e., around 1A−1, which wasalso detected for Na3PO4 [1].

Quantitative agreement between model pre-dictions and experimental data was obtainedunder the assumption that only the phosphate(and not the sulfate) ion rotation is observed inour experiment. The results strongly supportthe view of a dynamic coupling between cationsand anions in the Na2SO4-Na3PO4 system. Acomplete description of our results is given in [2].

1 1.5 21000 K/T

0.1

0.2

0.3

0.4

0.5

0.6

0.70.80.91.0

quas

iela

stic

line

wid

th/m

eV

x=0.5x=0.1x=0.0

xNa2SO

4·(1-x) Na

3PO

4

Fig. 1: T-dependent quasielastic linewidths.

0 0.5 1 1.5 2 2.5 3Q/Å

-1

0

0.5

1

1.5

2

2.5

3

quas

iela

stic

str

uctu

re f

acto

r

700 K600 K500 Kmodel Amodel B

x Na2SO·(1-x) Na

3PO

4x=0.5

Fig. 2: Quasielastic structure factors compared to modelpredictions.

[1] D. Wilmer, K. Funke, M. Witschas, R. D. Ban-hatti, M. Jansen, G. Korus, J. Fitter, and R. E.Lechner,Physica B, 1999,266(1&2), 60.

[2] D. Wilmer, H. Feldmann, R.E. Lechner,Phys.Chem. Chem. Phys., submitted.

113

EXPERIMENTAL REPORT

Quasielastic scattering from an unusual methylgroup linking Al atoms in the electron deficiency

compound [Al(CH3)3]2 ...

Proposal NCHE-03-181

Instrument V3

Local Contact

Lechner, Desmedt


10. 6. - 21. 6. 2001Principal Proposer: Michael Prager, Forschungszentrum JulichExperimental Team: Michael Prager, Forschungszentrum Julich

A. Desmedt, Hahn-Meitner Institut


Introduction

Group III trimethyl compounds are technicallyinteresting materials. Due to their thermal in-stability the materials can be used for dopingsemiconductors with Al, Ga, In and Tl by de-composition at hot surfaces. Aluminum alkylsare further used as Ziegler-Natta catalyst inpolymerization of olefins. These application aredue to the fact that the molecule is electricallynot saturated. For this reason trimethyl alu-minum forms dimers Al2(CH3)6 with each Alatom about tetrahedrally surrounded by methylgroups. Two metal ions linked by two weaklybond bridging methyl groups is a rather uniquephenomenon and focused scientific interest ontothis electron deficiency compound.


Quasielastic neutron spectra of Al(CH3)3 weremeasured at sample temperatures 13 < T [K] <234. The flat sample was oriented at 45o. Atλ=7A a resolution of52µeV is obtained. 70 de-tectors at large scattering angles 80 < 2Θ[o] <136 were summed up into one spectrum.Fitting different Lorentzians into the observed

quasielastic intensity requires to impose restric-tions to avoid correlation between parameters. 3inequivalent methyl groups of equal occurrenceprobabilities are known to exist from diffraction[1] and tunnelling spectra [2]. We fitted thespectra only for energy transfers below 2meVto avoid problem due to phonon intensity in-creasing with T. While the strong potential ofthe bridgingCH3 group enters the spectrometerrwindow in a well separated temperature regimethe similar barriers of the terminal groups canbe distinguished at low temperatures only wherethe relative difference of linewidths is largest (fig.

5 10 15 20 251000/T

1

1,5

2

2,5

3

log(

wid

th)

Figure 1: Arrhenius plot of the 3 quasielasticcomponents contained in the spectra

1). There is a strong Debye-Waller-factor relatedwith the soft dimeric unit. The fitted linewidthsfollow exponential laws with activation energiesEa = 14.5, 17.6 and 53.6 meV. Prefactors around4meV are characterisitic of the CH3 rotor. Lowactivation energies are combined with large tun-nelling transitions. The such derived potentialsrequire a new assignment of librational modes inthe density of states to reconcile QNS, tunnellingand DOS. The new interpretation also fits betterab-initio calculations (GAUSSIAN94). A com-prehensive paper is submitted for publication [3].The evaluation of the data from Ga(CH3)3 is

more difficult: the 6 inequivalent methyl groupsshow rather similar rotational barriers; a phasetransition detected in the experiment limits thetemperature regime to T ≤ 130K.

References[1] G.S. McGrady, J.F.C. Turner, R.M. Ibber-son, M. Prager, Organometallics 19,4398(2000)[2] M. Prager, H. Grimm, S.F. Parker, S.McGrady, Physica B276 - 278,250(2000)[3] M. Prager, H. Grimm, S.F. Parker, R.Lechner, A. Desmedt, S. McGrady, E. Koglin,to be published

114


EXPERIMENTAL REPORT Proposal N° CHE-03-0184Instrument V3Molecular dynamics in the incommensurate 2-

decanone/urea crystal Local Contact A. Desmedt

Principal Proposer: F. Guillaume, CNRS - Université Bordeaux I Date(s) of ExperimentExperimental Team: F. Guillaume

A. Desmedt, H.M.I. 13 - 18 / 08 / 2001


Aims of the experimentsUrea inclusion compounds are well known asprototypical incommensurate compositeorganic materials. In these crystalline solids theurea molecules form an extensively hydrogen-bonded helical "host" substructure withinwhich there are parallel one-dimensionalchannels that contain linear guest molecules.The repeat lengths along the channel axis of thehost substructure (ch) and of the guestsubstructure (cg) are incommensurate. In thisproposal, we focus on the 2-decanone/ureainclusion compound which displaysparticularly interesting temperature dependentstructural properties.The mean structure at room temperature of thehost subsystem is hexagonal P6122. Thediffuse scattering observed for 2-decanone/urea at room temperature reflectsthe strong disorder of the guest subsystem. Oncooling the sample the urea host substructureis unchanged but the 3-D ordering of the guestsubstructure is clearly evidenced through theapparition of new Bragg reflections and thedisappearance of the diffuse scattering lines.The aim of these experiments was toinvestigate the temperature dependence of thetranslational and rotational motions of the 2-decanone guest molecules in the channels ofthe urea inclusion compound.ExperimentsSelectively deuterated single crystals (needle-like) of CH3-CO-(CH2)7-CH3 / CO(ND2)2 wereplaced in slab containers so that the ureachannel axes were parallel to each other. Usingthis mosaic of single crystals, two scatteringgeometries were considered (Q and Q//)allowing the translational and rotationalmotions of the guest molecules to be probedindependently. The spectra were recorded onthe time-of-flight spectrometer NEAT at 4temperatures between 320 K and 200 K for Q

and between 300 and 100K for Q//. theaveraged energy resolution was about 60 µeV(0 = 6.3 Å).Main resultsThe spectra display a very nice quasielasticbroadening for the two experimentalgeometries considered in these experiments.

The analysis performed by fitting oneLorentzian function plus an elastic peak to theexperimental spectra provides the resolutiondependent EISFs (figures above).A run in the Q// geometry has also beenperformed at 100K and no quasielasticscattering could be observed. An inelasticfeature is seen at 1.8 meV (observed below 1meV in n-alkane/urea) suggesting stronginteractions between the ketone functionalgroup of the guest molecules and the N-Dbonds of the host substructure.In Q geometry, the data recorded for Q > 1.5Å-1 are unreliable because of coherentscattering. In addition the quasielasticbroadenings at 200 K are close to theinstrumental resolution so that a betterresolution (of the order of 30 µeV) wouldcomplement very nicely this set of results.

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5 2

Q//

200 K250 K300 K

EIS

F

Q / Å-1

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5 2

Q

200 K250 K300 K320 K

EIS

F

Q / Å-1

115

cnr


EXPERIMENTAL REPORT Proposal N° EFInstrument V3Dynamics of the chlorocyclohexane molecules in

their thiourea inclusion compound. Local Contact A. DESMEDT

Principal Proposer: A. DESMEDT, HMI Berlin Date(s) of ExperimentExperimental Team: F. GUILLAUME, LPCM, Univ Bordeaux I

J.C. SOETENS, LPCM, Univ Bordeaux IR.E. LECHNER, HMI Berlin

22/01/2001-29/01/00105/12/2001-12/12/2001


In thiourea inclusion compounds the hostsubstructure comprises a hydrogen bondedarrangement of thiourea molecules and contains 1-D channels within which guest molecules arelocated. Our aim is to elucidate, in these materials,the mechanisms of the phase transitions involvingthe guest molecules dynamics. This study requiresthe understanding of the relationship between theguest molecules dynamics and the symmetryproperties of the composite crystals.For the present experiment, we have chosen thechlorocyclohexane/thiourea-d4 C6H11Cl / CS(ND2)2.In this material, only one phase transition has beenobserved at about 192K [1]: phase I (above 192K)is rhombohedral ( c3R ) and phase II (below 192K)is monoclinic (P21/a). The dynamics of the guestmolecules has been investigated by means of IQNSspectroscopy and molecular dynamics simulations(MD) have been performed to help in theinterpretation of the experimental data. Here wereport the preliminary analysis of the guestmolecules dynamics in the high temperature phaseof their thiourea inclusion compound.The IQNS spectra were recorded on NEAT at298K, 270K, 245K, 220K, 195K and 180K withaverage resolution of 60eV (i=6.3Å) and at 180Kwith average resolution of 20eV (i=8.5Å). Semi-oriented polycrystalline samples were obtained byachieving the parallel alignment of several (about100) single crystals along the channel axes. Thesingle crystals were randomly oriented with respectto rotations about the channel axes. Theexperiments have been performed with the channelaxes parallel to the scattering plane (denoted Q//)and with the channel axes perpendicular to thescattering plane (denoted Q). To provide comparison with IQNS experimentaldata (Sexp(Q,)), the simulation-derived incoherentneutron scattering laws (SMD(Q,)) have beencalculated from MD trajectories for the Q// and Q

geometries and convoluted with the instrumentalresolution function. Both Sexp(Q,) and SMD(Q,)have been analysed by using the samemethodology, i.e. the individual S(Q,) functionshave been fitted for each scattering angle by meansof the sum of an elastic peak (EISF) and aLorentzian function. Fast motions were observedwith correlation time from 14ps at 195K to 4ps at298K (at Q=1 Å–1) and as seen on the figures, theresolution-dependent EISFs obtained by fitting

either Sexp(Q,) or SMD(Q,) exhibit large variationswhen changing the temperature.This good agreement between theoretical andexperimental approaches [2] allow us to elaborate,from the analysis of the MD trajectories [3], detailedmodels which form good and realistic basis foranalysing the experimental spectra. The combinedMD-IQNS analysis is also in progress for thespectra of the phase II (180K).

Comparison of the EISFs for chlorocyclohexane /thiourea-d4 for Q (top) and Q// (bottom) scatteringgeometries. Filled symbols: experiments at 195K(squares) and 298K (circles). Open symbols: MD at 198K(squares) and 298K (circles). Continuous line: MD withinfinitely high resolution.

References:[1] M.J. Jones et al, J. Chem. Soc. Faraday Trans. 92,273 (1996) [2] A. Desmedt et al, Appl. Physics A (2002), in press[3] J.C. Soetens et al, in preparation

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CHE-03-0185 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° CHE-03-185Instrument V3Protonic conduction mechanisms in perchloric

acid hydrate clathrate Local Contact A. DESMEDT

Principal Proposer: J.C. LASSEGUES, LPCM Univ. Bordeaux I Date(s) of ExperimentExperimental Team: A. DESMEDT, HMI Berlin

F.GUILLAUME, D.CAVAGNAT, LPCM Univ Bordeaux IR.E. LECHNER, HMI Berlin

26/12/2001-04/12/2001


It is well known that the proton exhibits a muchhigher mobility than all the other ions in aqueoussolution. This is due to its easy transfer from onevehicle to another in hydrogen bonded systems,according for example to the very simplifiedequations:

OH3+…OH2 OH2…OH3

+

OH-…OH2 OH2…OH-

The mechanism of this abnormal mobility (anddiffusivity) has stimulated a huge amount ofexperimental and theoretical work since more thanone century. However, characteristic parameters ofthe proton dynamics such as jump distances andjump rates remain difficult to determine.Our aim is to investigate the protonic conductionmechanisms in the solid phase (below 228K) of theHClO4,5.5H2O system. In this clathrate, the ClO4

-

anions are confined into the cationic water cageson which the protons H+ are delocalised. Severalgroups have studied the structure and conductivity(about 3 mS/cm at 220K) of this proton conductingclathrate hydrate [1,2]. From IQNS results recentlyobtained on the backscattering spectrometer IN10(ILL, Grenoble) [3], we have observed on thespectra recorded between 180K and 220K at leasttwo quasi-elastic components. A first one isprobably associated to the long-range translationaldiffusion of the protons through the host clathtratehydrate structure (characterised by a width(HWHM) of ~ 0.25eV at 220K and Q=1.96Å-1).The second one might be due to localised diffusivemotions of the protons (rotational motions of thewater molecules) which give rise to quasi-elasticbroadenings too large compared to the energywindow of IN10 ( 12eV). In view of these results, IQNS experiments havebeen performed on the time-of-flight spectrometerNEAT in order to analyse these localised diffusivemotions. The spectra were recorded on a powdersample as a function of the temperature and theenergy resolution (see the table below).

A B C D E Fo (Å) 10,5 8,1 6,3 5,1 5,1 5,1E (eV) 11 31 52 94 147 300

T (K) 220210200

220 220 220210200

220 220

Summary of the experiments performed on theHClO4,5.5H2O clathrate hydrate where the letter in theupper row denotes the configuration of the spectrometer.

For all the resolutions used at 220K, we haveobserved on the spectra a quasi-elastic broadening.In order to analyse qualitatively these observations,the widths HWHM (half-width at half-maximum) andthe EISFs (Elastic Incoherent Structure Factor) ofthese broadenings have been estimated by fittingthe experimental data with an elastic peak plus aLorentzian function. In the fitting procedure, theHWHMs have been constraint to be identical for allangles because of the very low quasielasticscattering intensity. For example on the figurebelow, the HWHMs and the EISFs (at T=220K andQ=1Å-1) exhibit a strong dependence on the energyresolution. These variations suggest that thelocalised diffusive motions are characterised byseveral quasi-elastic components exhibitingdifferent Q-dependence. These components are probably due to therotational motions of H2O and H3O+ moleculeseffective within a timescale ranging from thenanosecond to the picosecond. Thus, furtheranalysis of the whole set of data should providenew information about the protonic conductionmechanisms in the perchloric acid hydrateclathrate.

0

50

100

150

200

250

300

350

0 50 100 150 200 250 300 350Energy resolution E (eV)

HW

HM

( eV

)

00,10,20,30,40,50,60,70,80,91

EISF (Q=1A

-1)

A B C D E F

HWHMs (filled circles; left scale) and EISFs (openedcircles; right scale) extracted from the IQNS spectra(Q=1Å-1 and T=220K) recorded on the HClO4,5.5H2Oclathrate hydrate. The letters above the graph refer to thedifferent configurations of the NEAT spectrometer (seetable).

References:[1] D. Mootz et al, J. Am. Chem. Soc. 109, 1200 (1987)[2] M. Cappadonia et al, J. Chem. Phys. 101, 7672(1994)[3] A. Desmedt et al, ILL Exp. Report N°7-07-175 (2001)

117


EXPERIMENTAL REPORT Proposal N° MAT-03-0189Instrument NEATNeutron scattering investigation of superconducting

ceramics Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3Ox Local Contact Dr.R.Lechner

Principal Proposer: Dr I.Padureanu NIPNE-HH,Bucharest Date(s) of ExperimentExperimental Team: Dr.R.Lechner HMI

D.Aranghel,A.Radulescu NIPNE-HH,BucharestJ.Pieper HMI

14-18 January 2002

Date of Report: 25 February 2002

The main purpose of this report is to present ashort description of the experiment and of thepreliminary results obtained from the slowneutron scattering measurements on a hightemperature superconducting material takenon the time of flight spectrometer NEAT ofBENSC .This spectrometer has beensuccesfuly used to obtain the results presentedin the papers [1,2] .In this study we have usedcold neutrons with =5.1 A and a resolutionE=98eV,(full width at the half maxim of theelastic line of a vanadium sample) Thescattering spectra were taken with 140detectors in a large angular range 15.410

134.5.0 All runs were measured within thetemperature range 100K-300K.The final dataare obtained at 28 scattering angles as afunction of the energy transfer for 4temperatures (100K,110K,130K and 300K)Thepreliminary data presented in Fig.1 for 3temperatures at 300K,110K and 100Kcorresponding to the normal,transition andrespectively to the superconducting state are analysed in terms of the generalized phononfrequency distribution(GFD).The preliminaryconclusions could be summarized as follows:- GFD obtained from an averaging over thefinal scattering vectors within a large range ofscattering angles(Bredov and Oskotskijmethod) at 3 temperatures are presented inFig .1 ;- Well resolved peaks at 5.57meV,10.43meV,19.38meV, 29.68meV, 67.42meV and 109.48meV were observed in GFD at 300K,5.21meV, 10.39meV, 24.51meV, 45.42meV,59.5meV, and 69.29meV at 110K and5.7meV, 10.26meV, 20.46meV and 44.44meV

at 100K;-The presence of the first three excitationsincluding the first soft mode at 5.20.5 meVfor all temperatures during the transition fromnormal to the superconducting state ;-A strong temperature dependence of the high

energy limit of the frequency spectra.

0 20 40 60 80 100 120 140 160 180 2000

10000

T=300K

0 20 40 60 80 100 120 140 160 180 2000

10000

T=110K

0 20 40 60 80 100 120 140 160 180 2000

10000

Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3Ox

g(h

) [ar

b.un

its]

h[meV]

T=100K

Fig.1 Temperature dependence of the generalizedphonon density of states

References:

[1]I.Padureanu,R.E.Lechner,D.Aranghel,A.Radulescu, A.Desmedt, J.Pieper,Applied Physics A(2002)in press

[2]A.Radulescu R.E.Lechner, I.Padureanu,C.Postolache,Applied Physics A (2002),in press

118

ef_13 // brandt // 21.03.02

EXPERIMENTAL REPORT Proposal N° *Instrument NEAT / V3The Investigation of microscopic

Dynamics of ZnCl2 Local ContactLechner R. E.

Principal Proposer: Russina M., Los-Alamos NLMezei F Russina O, HMI, Berlin Date(s) of Experiment

Experimental Team: Mezei F.,Russina M., Russina OLechner R. E., Pieper J., Desmedt A., HMI, Berlin 17/02- 10/03/2001

The goal of the project „The Investigationof the Microscopic Dynamic of the Inorganic GlassFormers” is to study the microscopic dynamics inglasses with different degrees of fragility. It is wellknown, that the majority of the glass formers showa specific temperature behavior of viscosity aroundthe glass transition, which deviates from theArrhenius law [1]. The larger the deviation fromsimple Arrhenius temperature dependence, themore fragile is the system, and the larger is thedegree of fragility m [2]. How this macroscopicproperty is reflected on microscopic dynamic ofglasses is still an opened question. The specificfeatures of microscopic dynamics in glasses are theso-called Boson peak and the picosecond -processgiving rise to strong anharmonic increase ofintensity in the picosecond time range. It wassuggested that the Boson peak is caused byvibrational excitations (despite the exactmechanism is unclear), while the nature of -process is still controversial

The inelastic neutron scattering experimentwith strong glass ZnCl2 (fragility m=30) wasperformed on the time-of-flight spectrometerNEAT. The microscopic dynamics of the samplewas investigated in a broad temperature range(from 300 K to 660 K), which correspond to glass,supercooled and liquid states. Fig 1 shows the TOFinelastic spectra taken at different temperatures andat Q=1 Ǻ-1.

At the temperatures below and aroundglass transition (373 K and 393 K) the spectrashow a harmonic behavior with a clearlypronounced Boson peak at E ~3 meV. Theanharmonic increase of intensity at low energytransfer E < 3 meV (picosecond range) occurs atthe temperatures higher than the glass transitiontemperature (570K and 605K). This increasecorresponds to ß-process , which was observedfirst time in this glass former by inelastic neutronscattering experiment.

We calculated the relative strength of theß-process as a ratio mr of inelastic intensities atE=0.5meV and E=0 meV at Q corresponds to the

value of the pre-peaks of the structure factors. Wefound that intensity of the ß-process in strong glassZnCl2 is 3 times smaller as in extremely fragileglass Ca0.4K0.6(NO3)1.4 (fragility m=93 [2]). Incontrast the Boson peak in ZnCl2 is more distinctthat in CKN and has the relative intensity mv 2.15,while fragile CKN only 1.14 ( mv was calculatedas the ratio of the Boson-peak intensity to theintensity of the minima at E=0.5 meV).

119
Seite 1 von 1
Fig1. TOF inelastic spectra of “strong” glass ZnCl2.Boson peak presents in spectra at temperature belowand closed to Tg (Tg≈387±3K). The anharmonicincrease of intensity is apparent in the data at 570Kand 605K..

Our results contradict the hypothesis that the ß-process originates from soft vibrations orvibrational relaxation. Following these theories theß-process should to be stronger pronounced insystems with stronger vibrational properties, i.e. insystem with more distinct Boson peak . In contrastwe observed the much smaller value mr in thestronger glass ZnCl2 that in CKN [3]. However, thefinal answer about the nature of the ß-process canbe given only after the accurate analyze of the Q-dependence of the dynamic structure factor, whichis now in work.

1. C. A. Angell , J.Phys.Chem.Solids, 49, 863, (1988).2. R. Boehmer et al, J.Chem.Phys., 99,4201, (1993).3. F. Mezei and M. Russina, J.Phys.: Condens. Matter11, A 341,(1999)

0 1 2 3 4 50.000

0.001

0.002

0.003

0.004

0.005

0.006ZnC l2, Q = 1 Å -1

T = 373 K T = 393 K T = 570 K T = 605 K

energy transfer [m eV]

S(Q

,)/n

b


4 6 8 100.0

0.4

0.8

1.2

1.6

2.0Figure 2

x1 = 90 % x1 = 70 % x

1 = 50 %

x1 = 30 %

CCl4Methanol

Gdist(r)

r, Angstrom


Instrument E9Hydrogen-bonded structures in methanol/CCl4mixtures Local Contact

Daniel Többens

Principal Proposer: Francesco Aliotta, ITS-CNR-Messina-ITALY Date(s) of ExperimentExperimental Team: Cirino Vasi, ITS-CNR-Messina-ITALY

Franz Sajia, ITS-CNR-Messina-ITALYRosina Ponterio, ITS-CNR-Messina Italy

*26 Nov-3 Dec 2001

Date of Report: *

The aim of this experiment was to investigatethe local coordination in methanol/CCl4mixtures, in order to check the validity of theworking hypothesis of the existence ofpolymeric clusters with a relatively largeaggregation number at enough high methanolconcentration. Such an hypothesis has beensuggested by previous experimental resultsfrom Raman scattering and dielectricrelaxation measurements.

The experiment has been performed on fullydeuterated methanol. A wavelength of 1.797 Åhas been selected for the incident neutrons.The instrument angular resolution was of 0,1°.The scattered intensity profiles has beencollected on the Q range .3 Å-1Q 7 Å-1. Puremethanol and CCl4 have been investigated,together with their mixtures at the methanolconcentration (volume fraction) of 0.02, 0.11,0.30, 0.50, 0.60, 0.70, 0.75, 0.80. In the figure1, we report, just as an example, some of theexperimental results, as obtained afternormalization with the scattering from avanadium sample and subtraction of the cellcontribution.At the same time we are performing somenumerical simulations of the mixture by meansof the Molecular Dynamics (MD) technique.We are using a site-site interaction modelcontaining a Coulomb and Lennard-Jonesterm. The potential parameters and the

geometry for methanol and CCl4 were takenfrom the literature (R. Veldhuizen and S. W. deLeeuw, J. Chem. Phys. 105 2828 (1996)).We are investigating the whole compositionrange evaluating the intermolecular total paircorrelation functions as an appropriateweighted sum of the partial pair correlationfunctions (PDF).

After reducing the experimental data we aregoing to Fourier transform and compare theexperimental total PDFs with those obtainedfrom the MD simulation (see figure 2). We are also interested to understand the roleplayed by the non-polar solvent (CCl4) on theintermolecular structure of the methanol andmore specifically on the hydrogen bonddistance. In the pure methanol the peak at 2.8Å is indicative of the hydrogen bond. From apreliminary analysis we observe a slight shift ofabout 0.1 Å in the position of this peak whichis present over the whole range of compositioninvestigated. This finding requires furthercomparison with the experimental data.

1 2 3 4 5 6 70

500

methanol(50%)

methanol(70%)

methanol(100%)

CCl4

Intensity

Å-1

120

A. Triolo Page 1 23.03.02C

EXPERIMENTAL REPORT Proposal N° MAT-03-159Instrument NEATSegmental Dynamics in Polymer ElectrolytesLocal Contact R. E. Lechner

Principal Proposer: R. Triolo, University of Palermo, Italy Date(s) of ExperimentExperimental Team: A. Triolo, HMI

F. Lo Celso, University of Palermo, Italy 24-31/03/2001

Date of Report: *

As a continuation of a previous experimentcarried out on NEAT [1, 2] (Year 2000 BENSCreport no. CHE-03-121) we further exploredthe dynamics of polymer electrolytes. Inparticular the QENS technique was applied tothe investigation of the segmental dynamics ofpure Polyethylene oxide (PEO) and PEOdoped with the inorganic salt Li-BETI.

In our previous set of experiments wecharacterised the existence of a dynamicheterogeneity in the polymer segmentaldynamics as a consequence of the saltaddition. This effect which had been foreseenfrom Molecular Dynamics simulations [3] canbe rationalised assuming that the polymerlocally complexes the Li+ cation, so thattransient crosslinks may form. Their effect isthe one to slow down the segmental relaxation.Accordingly we noticed that, as a consequenceof salt addition, the QENS pattern from dopedPEO can be described in terms of two dynamiccomponents: one corresponding to the purePEO and another, slower, componentassociated to the complexed PEO.

In the present experiment we further extendedthe existing data set. In particular we studied alower molecular weight (100,000) PEO ascompared with our previous experiment. This choice was due to the fact that high MW(4,000,000) PEO shows an unresolved slowdynamic component at the used instrumentalresolution (90 eV). As we aim to probe slowprocesses superimposed to pure PEOdynamics we tried to reduce this effect.A direct comparison between the two fractionsof pure PEO shows that the chosen strategy iscorrect as no indications of unresolveddynamics is found at 160 C for the lowmolecular weight fraction. Moreover the comparison between pure anddoped PEO shows that the slowing downeffect occurs also in the case of the low MWfraction (see Figure 1). At present the analysishas not been concluded yet, so we cannot

confirm whether the proposed heterogeneitycan be found also in the more recentexperimental data.

At the present stage, however, our attentionhas shifted to a deeper characterisation of thedynamics of pure PEO, which seems to have ahigher degree of complexity than supposed. Inparticular by proper fit of the FourierTransformed QENS data the existence of threedifferent coexisting dynamic processes hasbeen characterised in pure PEO [4]. We nowplan to extend the analysis to doped PEO tounderstand the effect of salt addition to suchprocesses.

References

[1] A. Triolo et al., Physica B, 301, 163 (2001)[2] A. Triolo et al., Physica A, 304, 308 (2002)[3] O. Borodin et al., Macromolecules, 33,2273 (2000)[4] A. Triolo et al., Manuscript in preparation(2002)

Figure 1.

121


EXPERIMENTAL REPORT Proposal N° MAT-03-0188Instrument NEATQENS Study of the Dynamics of Confined PEO-

salt Systems Local Contact R. E. Lechner

Principal Proposer: R. Triolo, University of Palermo, Italy Date(s) of ExperimentExperimental Team: A. Triolo, HMI

V. Morreale and V. Baiata, Univ. Palermo, ItalyJ. Pieper, HMI

30/7-5/8/2001

Date of Report: *

In the last years our group has been active inthe characterization of the dynamic propertiesof Polymer Electrolytes. This class of materialscan be exemplified by Polyethylene oxidedoped with a salt such as Li-CF3SO3. Theelectrochemical performances of thesematerials are of large interest for a variety ofapplications, due to the high conductivity of thedoped polyethers. This effect is theconsequence of the complexing of the Li+cation by the oxygen atoms in the polyetherchains. Accordingly the salt dispersed in thepolymer matrix is solvated and the ions areable to conduct the current. However, one ofthe major drawbacks of these materials is thatthey are crystalline, as PEO can lead toformation of highly regular lamellar structureswhere the conductive process is not aseffective as it is in the melt phase.In order to solve this limitation, differentapproaches have been introduced, such as theaddition of low molecular weight additives,which prevent the crystallization.Recently it has been proposed that confiningthe polymer in pores whose size is sufficientlysmall, the crystallization can be prevented, dueto steric effects and so the polymer remainsamorphous even below its crystallizationtemperature [1].

We decided to probe the polymer dynamics insuch confining conditions, in order tounderstand the details of such an effect.Accordingly PEO was confined in an inorganic-organic rigid matrix whose pores highly hinderthe PEO chain, so reducing the crystallineportion. Apart from general interest, this study is also ofrelevance, as it allows extending thecharacterization of amorphous PEO dynamicsat low temperatures where the polymer isgenerally highly crystalline and so thedynamics is considerably slowed down. QENS measurements on pure and confinedPEO were collected on NEAT and also

backscattering data were collected on IN16(ILL).In Figure 1 the IN16 data are reported to showthe effect of confinement: the pure PEO ischaracterised by a slow dynamics up to 330 K,where it melts. At higher temperatures thesegmental relaxation is too fast to be probedon a backscattering instrument.In the case of the confined PEO, the dynamicsbecomes fast enough to be probed at ca. 200K, that corresponds to the Tg for PEO. Athigher temperatures it is possible to probe thesegmental relaxation.NEAT data have been collected for PEO-600at different temperatures in the range between320 and 400 K, both for the pure and theconfined polymer. Analysis is now in progressto characterise the difference between thepure and confined PEO dynamics.

References[1] L. M. Bronstein et al., Chem. Mater., 13,3678 (2001)

Figure 1

122


0.1 10.1

1

10

100

1000

d(Q

)/d

(cm

-1 sr

-1)

Q (nm- 1)

D-PEO D-PEO

1 5/LiI

0.1 1

10

100

1000

d(Q

)/d

(cm

-1 sr

-1)

Q (nm-1)

D-PEO + H-PEO (30/70) D/H(30/70)-PEO15/LiI

EXPERIMENTAL REPORT Proposal N° MAT-04-590Instrument V4Structural Microheterogeneities in PEO-Salt

Mixtures Local Contact P. Strunz

Principal Proposer: Roberto Triolo, University of Palermo (Italy) Date(s) of ExperimentExperimental Team: Alessandro Triolo, HMI-BENSC

Fabrizio Lo Celso, University of Palermo 13-21-2-2001


Solid Polymer electrolytes, such aspolyethyleneoxide (PEO) doped with alkalysalts, have been shown to constitute a novelclass of materials with high potentials forapplications in the field of consumerelectronics products. Most of the appealingfeatures are strictly related to the formation ofstrong correlations between the salt cation(generally Li+ or Na+) and the polar portion ofthe polymer chain. Small Angle NeutronScattering measurements were performed onPEO-LiI mixtures and, in order to characterizelabile clusters induced by the existence of thecomplexes, we decided to compare thescattering pattern from fully deuterated PEO(D-PEO) and two mixtures D-PEO20-LiI and D-PEO10-LiI. The materials were chosen tominimize the incoherent signal arising from Hatoms, so to detect the presence of D-PEO-Liclusters embedded in a matrix of pure D-PEO.In Figure 1 a comparison between the SANSpatterns from D-PEO and D-PEO doped withLiI is reported. Apart from differences in theconstant incoherent term depending on thedifferent sample compositions, there are nomajor differences in the large Q range. In thisQ range, in the case of PEO-salt mixtures, wewould expect to find indications of theexistence of static heterogeneities due to thecomplex interaction between PEO and Li+cation. Up to Q=3.2 nm-1, there are noindications that any aggregate is existent. ThisQ value would be related to cluster sizescorresponding to r > 2/Q 20 Å. Accordinglyat this stage, our SANS evidences exclude theoccurrence of static clusters whose size islarger than ca. 20 Å. In order to get detailsabout the morphology of PEO-salt solutions,mixtures of D-PEO and H-PEO were studiedwith and without salt addition. In Figure 2 wecompare the SANS patterns from H-PEO+D-PEO (70/30) and H-PEO+D-PEO (70/30) + LiI(such that the overall composition is PEO15-LiI). The data can be described in terms of arandom coil model and fitting leads to slightlydifferent values for the radius of gyration for

the two mixtures, in particular Rg,PEO=55.4 Å,while Rg,PEO/LiI=53.5 Å. These results indicatethat the effect of salt addition is the one toinduce a slight collapse of the random coilconfiguration of PEO chains, as aconsequence of the interactions between PEOchains and the cation.

Fig. 1. SANS patterns from pure fully deuterated PEO (D-PEO)and LiI-doped D-PEO (D-PEO15=LiI) at 75 °C.

Fig. 2. Comparison between SANS patterns from a pure mixtureof D-PEO and H-PEO (ratio H-PEO/D-PEO = 70/30) and LiIdoped 70/30 H/D-PEO (with composition PEO15–LiI). The linescorrespond to a fit with a random coil model.

123

CHE-03-0160 // brandt // 23.03.02

EXPERIMENTAL REPORT Proposal N° CHE-03-160

Instrument V3Local dynamics of polyethyleneLocal Contact J. Piper, A. Desmedt

Principal Proposer: Arrighi, V. – Heriot-Watt University (UK) Date(s) of ExperimentExperimental Team: Arrighi, V. – Heriot-Watt University (UK)

Arialdi, G. – ULB (Brussels, BE)Saggio, F. – Heriot-Watt University (UK)

19-24.03.2001

Date of Report: September 2001

The aim of this experiment was to investigatethe dynamic behaviour of polyethylene (PE)melts, using neutron scattering.

Recently Qiu and Ediger (1) used 13C NMR tostudy melt dynamics in various PE samples ofdifferent molar mass. Our aim was to establishwhether QENS measurements carried out onthe same samples revealed similar features tothose reported by Qiu et al.(1). Moreimportantly, the molecular weight dependenceof the local dynamics measured by QENSprovided an experimental basis for directcomparison with Molecular Dynamics (MD)simulations carried out by Prof. J.P. Ryckaert‘sgroup (Universite’ Libre de Bruxelles,Belgium).

QENS measurements were performed on theNEAT spectrometer on three PE samples: n-tetratetracontane (n-C44H90), and PE withMw=2150 and 108000 g mol-1. Spectra werecollected at several temperatures in the range400-480 K (above the melting point of PE).

The time-of-flight data were converted toenergy transfer and then the Ingrid code wasapplied to transform the incoherent dynamicstructure factor at constant angle to theequivalent quantity at constant Q. Examples ofQENS spectra are given in Figure 1. Theexperimental data are well described by amodel function which is the Fourier transformof a stretched exponential (or KWW)(convoluted with the instrumental resolution).

Our QENS results are in excellent agreementwith the NMR measurements of Qiu et al. (1)and we observe the same temperaturedependence of the characteristic relaxationtime. As expected, the characteristic time ofthe dynamic process, at any giventemperature, increases with increasing molarmass. This is shown in Figure 2 where wecompare the intermediate scattering function

(determined from the experimental data usingFURY) of C44H90 and PE2K.

Dssitfd

R((

1

124

etailed comparison between experiments andimulations has been made. The results will behortly submitted for publication (2). As shown

n Figure 2, there is good agreement betweenhe intermediate scattering functions calculatedrom the MD trajectories and the experimentalata, particularly for C44H90.

0.0

1.0

2.0

3.0

-1 0 1 2 3 4 5Energy Transfer (meV)

S(Q

, )

2

2

0

3

1

Figure 1- QENS spectra of C44H90 at 450 K and Q = 0.5, 0.75and 1.75 Ă-1 (symbols: experimental data, lines: fits)

0 5 10 15 20

0.01

0.1

1

S(Q

,t)

time (ps)

Figure 2 – Intermediate scattering function of C44H90 (emptysymbols) and PE2K (filled) at 450 K and Q = 0.5, 0.75 and 1.5Ă-1. The lines correspond to MD calculations for C44H90 (dot-dash) and PE2K (continuous line)

Seite 1 von 1

eferences:1) Qiu et al. Macromolecules 33 (2000) 4902) Arialdi et al. Macromolecules, in

preparation


EXPERIMENTAL REPORT Proposal N° :CHE-03-0191Instrument V3Local dynamics of selective deuterated

Liquid crystalline polymers Local Contact *A.DESMEDT

Principal Proposer: V.Arrighi, Chemistry Department, Heriot-WattUniversity, UK Date(s) of Experiment

Experimental Team: V.Arrighi, Heriot-Watt University, UKH.Qian, Heriot-Watt University, UKA. Desmedt, BENSC

30Aug –04 Sep 2001

Date of Report: 25 Jan 2002

The aim of this experiment is to enhance ourunderstanding of the local dynamics of main chainliquid crystalline polymers (LCPs). QENSmeasurements were performed on a semiflexible liquidcrystalline copolyester of 4,4'-dihydroxy,, '-dimethylbenzalazine:

with n=8(50%) and n=10(50%). Samples selectivelydeuterated in the rigid mesogen unit (D8) and flexiblespacer (D2) were used to separate the motions of the twosegments. These materials have a calorimetric glasstransition (Tg) at 25C, melting temperature (Tm) at144C and a nematic to isotropic transition temperature(Ti) at 220C.

Quasielastic neutron scattering (QENS) measurementswere carried out on the time-of-flight instrument NEAT.The scattered intensity was monitored at selectedtemperatures in the range Tg to Ti, chosen to match dataalready available from experiments carried out on IRIS(ISIS, UK). The S(,) data at constant angle wereconverted to scattered intensity at constant Q usingINGRIDQ.

As illustrated in figure 1, quasielastic broadening wasobserved throughout the experimental temperature range,a result that is consistent with the IRIS data. Due to thesemi-crystalline nature of the samples, at temperaturesup to Tm, the scattering consists of elastic andquasielastic components. Above Tm full broadening ofthe elastic line is observed.

Preliminary data analysis was carried out using astretched exponential or KWW function to model thequasielastic component. As shown in figure 2, thisapproach gives a good description of the QENS data.Above Tm, molecular motion is characterised by Q-independent values in the range 0.35~0.41 and Qdependent characteristic times =0Q-n with 0 = 5.18meV-1 and n=3.35 at T=468 K.

Low values are generally indicative of broaddistributions of relaxation times. However, they mayalso be a result of using a single process to characterisedistinct motions occurring on different time scales. We

are in the process of combining information fromdifferent spectrometers in order to clarify this issue.

Figure 1 - QENS spectra of D8 at Q= 1.44Å-1, as afunction of temperature.

Figure 2 - QENS data of LCP D8 at T=468 K (symbols refer toexperimental data and the lines represent fits using the KWWfunction convoluted with the instrumental resolution).

The LCPs deuterated in the mesogen (D8) and theflexible spacer (D2) show almost identical quasielasticbroadening at all temperatures. This supports the ideathat the dynamics of the rigid mesogens and that of theflexible spacers are strongly coupled.

-1 -0.5 0 0.5 1 1.5 2

Energy Transfer (mev)

S(Q

, )

Vanadium

T=373K

T=412K

T=442K

T=468K

O C

CH3

N N C O C

O

CH2n

C

CH3 O m

0.00

0.01

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,

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125


EXPERIMENTAL REPORT Proposal N° CHE-03-0197Instrument SPANCollective Dynamics in atactic PolypropyleneLocal Contact A. Triolo

Principal Proposer: V. Arrighi, Heriot-Watt University, Edinburgh,UK Date(s) of Experiment

Experimental Team: F. Saggio and P. Holmes, HWU, UKA.Triolo, HMIC. Pappas, HMI

8-21/10/2001

Date of Report: *

In the last few years our team has been activein characterising the dynamic properties ofatactic Polypropylene (aPP) with neutronscattering techniques [1-3] and comparingthese findings with results from complementarytechniques such as Molecular Dynamicssimulations. Recently the use of MD methods has allowedrationalisation of a variety of experimentalobservations in polymer dynamics [see e.g. 4].In reference [3], we reported a first comparisonbetween MD and QENS results on the singleparticle dynamics in aPP as obtained frominvestigation of the dynamic incoherentstructure factor (ISF). The dynamic collective structure factor (CSF),which can be derived measuring the coherentscattering from a fully deuterated samplecontains additional information as compared tothe ISF, as it contains details on theinterparticle correlation relaxation.

In the past [5], it has been shown that the time-temperature nature of the collective relaxationcorresponds to the one derived from viscositymeasurements, thus indicating that theinvolved processes are the same.

The CSF strongly depends on the momentumtransfer Q. Accordingly, we started to explorethe Q-T space nature of the relaxation functionS(Q,t) in the low Q region, in proximity of thefirst intermolecular interference peak (Figure1). In our previous investigations we explored theCSF of D-aPP by means of Neutron Spin Echoat temperatures between 280 and 400 K atQ=0.74, 1.1 and 1.45 Å-1. These Q values arecovering the first S(Q) peak, and we showedthat the time temperature behaviour follows theone derived by viscosity measurements. Up tonow technical limitations did not allow themeasurements of NSE patterns at high Qvalues such as the ones corresponding to thesecond maximum of the S(Q) in aPP (i.e.around 3.0 Å-1. With the recent technicaldevelopments at SPAN it is now possible toachieve an incoming neutron wavelength of 3Å which allows covering the high Q range thatwas inaccessible before. Accordingly wecollected NSE data around the peak centred atQ=3.1 Å-1 in the temperature range between260 and 360 K. Data are now in the process ofbeing reduced and analysed to check thedynamic behaviour in this Q range above theglass transition of aPP.

References[1] V. Arrighi et al., Physica B 301, 157 (2001)[2] V. Arrighi et al., Physica B 301, 35 (2001)[3] V. Arrighi et al., Macromolecules, 2002,accepted[4] K. Karatasos et al., Macromolecules, 34,7232 (2001)[5] D. Richter et al., Macromolecules 31, 1133(1998)

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)

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Figure 1

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EXPERIMENTAL REPORT Proposal N° PHY-03-161Instrument V3Dynamic Features of Hydration Water interacting

with Hydrophobic Molecules Local ContactR.E. Lechner, J.Pieper

Principal Proposer: V. Calandrini, Phys. Dept., Univ. of Parma-I Date(s) of ExperimentExperimental Team: A. Deriu, Phys. Dept., Univ. of Parma-I

G. Onori, Phys. Dept., Univ. of Perugia-IR.E. Lechner, BENSC,HMI, Berlin–D

12-18 Feb. 2001

J. Pieper, BENSC,HMI, Berlin–DDate of Report: 29 Jan. 2002

Trimethyl-amino-N-oxide, (CH3)3NO, (TMAO)and tert-butyl alcohol, (CH3)3COH, (TBA) arehydrophobic molecules with the samehydrophobic moiety and a different polargroup. They can be used as model systems tostudy how hydrophobic molecules in aqueoussolutions affect water dynamics. We reporthere first results of a QENS experiment onH2O/TBA and H2O/TMAO mixtures at differentsolute concentration in the range 0-2 mol %.We used perdeuterated solutes in order tominimise the scattering from TBA and TMAO.The measurements were performed usingNEAT at 5.1 Å wavelength (energy resolutionE = 64eV (FWHM)), and at a fixedtemperature, T=20°C.The simplest approach to the analysis ofincoherent QENS spectra of H2O is to assumea scattering law with two Lorentziancomponents. A broader one describing the‘local’ proton dynamics connected to the‘rattling' motion of a water molecule inside the‘cage' formed by its nearest neighbours, and anarrower one describing the long-rangediffusion that follows the relaxation of thesewater cages. The Q-dependence of the width of the narrow component can be described bya random jump model [1] in terms of atranslational diffusion coefficient, D, and aresidence time, 0, between subsequent jumps((Q) = DQ2/(1+DQ2

o)). The broadening of thenarrow component for different soluteconcentrations is shown in fig. 1 for TBA/H2Osolutions. The variation of D (fig.2), and 0(data not shown) upon increasing soluteconcentration up to ~2% mol shows that themobility of water is appreciably reduced in bothsystems. We may note that up to thisconcentration value there is no associationamong solute molecules and the effectsobserved can therefore be attributed to thehydrophobic hydration alone. The diffusioncoefficient of water in 2.2 mol% TBA/ H2Osolution, 1.5 10-5cm2s-1, is 40 % smaller than

that of pure water, 2.5 10-5 cm2s-1. Thisdecrease is in agreement with the picture thatthe diffusivity properties of water inhydrophobic hydration shells are comparableto those observed in pure water in supercooledregime [2].Acknowledgments: The experiment atBENSC in Berlin was supported by theEuropean Commission under the Access toResearch Infrastructures Action of the HumanPotential Programme (contract HPRI-CT-1999-00020).

0 1 2 3 4 5 60

100

200

300

400

(

eV)

Q2(A-2)

H2O xTBA=1.0mol% xTBA=2.2mol%

Fig 1 Quasielastic broadening vs.Q2 fordifferent TBA aqueous solutions.

0,0 0,5 1,0 1,5 2,0 2,51,41,61,82,02,22,42,6

H2OTMAOTBA

X (mol%)

D x

105 (c

m2 s-1

)

Fig 2 Translational diffusion coefficient, D,vs. solute concentration.

1. P. Egelstaff, An Introduction to the Liquid State(Oxford Sci. Publ. 1994) 221.

2. F. Cavatorta, A. Deriu, D. Di Cola, H. D.Middendorf, J. Phys.:Condens. Matter 6 A113(1994).

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Instrument V3Dynamic Features of Hydration Water interactingwith Hydrophobic Molecules

Local ContactR.E. Lechner, J.Pieper

Principal Proposer: V. Calandrini, Phys. Dept., Univ. of Parma-I Date(s) of ExperimentExperimental Team: A. Deriu, Phys. Dept., Univ. of Parma-I

G. Onori, Phys. Dept., Univ. of Perugia-IR.E. Lechner, BENSC,HMI, Berlin–D

6-12 Aug 2001

J. Pieper, BENSC,HMI, Berlin–DDate of Report: 29 Jan. 2002

Trimethyl-amino-N-oxide, (CH3)3NO, TMAO)and tert-butyl alcohol, (CH3)3COH, TBA)molecules have the same hydrophobic moietyand different polar groups. They can be usedas model systems to study dynamic propertiesof water involved in hydrophobic hydrationshells and the effect of different polar groupson the hydration properties of moleculeshaving the same large a-polar group. Theexperiment reported year follows a previousone performed in February 2001. Theseprevious measurements showed that at roomtemperature the effect of an increasinghydrophobic solute concentration is to slowdown water dynamics leading to spectrasimilar to those obtained in pure water in thesupercooled regime. These hydrofobic effectsare expected to be T-dependent. We havetherefore studied the temperature dependenceof QENS on H2O/TBA and H2O/TMAOmixtures, in the range 0. T 50 °C, at 0.02mole fraction of the perdeuterated co-solvents.The measurements were performed usingNEAT at = 6 Å (energy resolution E=50 eV(FWHM)). The data were analysed assuming ascattering law with two Lorentzian componentsas described in the previous report (see N°PHY-03-161). . A broader one describing the‘local’ proton dynamics, and a narrower onedescribing the translational diffusion. The Q-dependence of the narrow component, Γ, hasbeen described by a random jump model [1] interms of a translational diffusion coefficient, D,and a residence time, 0, between subsequentjumps. The diffusion coefficient vs.temperature is shown in Fig. 1 for TBA andTMAO solutions and pure water as reference[2-4]. A preliminary analysis shows thefollowing features: the introduction ofhydrophobic molecules decreases the diffusioncoefficient with respect to that of pure water inthe whole temperature range explored. InTMAO solutions D is systematically smaller inTBA solutions at the same concentration. This

difference increases at higher T, where thehydrophobic effects are less relevant. Thedifference between TBA- and TMAO solutionscan be attributed to the presence of a differentpolar group with a dipole moment three timesbigger in TMAO than in TBA. The residencetime 0 decreases upon increasing T in bothsystems (data not shown). The average jumpdistance, L, derived from the relationL=(6D0)1/2, is T-independent throughout themeasured range (L ~ 1.1Ǻ in TBA- and 0.9 Ǻin TMAO-solutions). These results are inqualitative agreement with MD simulationssuggesting that water molecules are moretightly coordinated by TMAO than by TBA [5]. Acknowledgments: The experiment atBENSC in Berlin was supported by theEuropean Commission under the Access toResearch Infrastructures Action of the HumanPotential Programme (contract HPRI-CT-1999-00020).

240 250 260 270 280 290 300 310 320 3300,00,51,01,52,02,53,03,54,04,55,0

Dx1

05 cm2 s-1

T(K)

TBA 2mol% TMAO 2mol% H2O from ref. 2 H2O from ref. 3 H2O from ref. 4

Fig 1 Translational diffusion coefficient, D, vs.T forTBA aqueous solution.

1. P. Egelstaff, An Introduction to the Liquid State(Oxford Sci. Publ. 1994) 221.

2. K.T. Gillen et al. J. Chem. Phys.57, (1972),5117.

3. L.A. Woolf J.C.S. Faraday I, 71, (1975), 784.4. K. R. Harris and L.A. Woolf, J.C.S Faraday I,

76, (1980) 377.5. L.Fornili et al. J.C.S. Faraday Trans., 91,

(1995), 3803.

128


EXPERIMENTAL REPORT Proposal N° PHY-03-0182Instrument V3 NEATDiffusion of sheared liquidsLocal ContactR.E. Lechner, J. Pieper

Principal Proposer: Max Wolff, Kristallographie Univ. Erlangen Date(s) of ExperimentExperimental Team: Andreas Magerl, Univ. Erlangen, Bernhard

Frick, ILL, Hartmut Zabel, RU BochumR.E. Lechner, J. Pieper, A. Desmedt, HMI

6.9-10.9.20011.10-8.10.2001

Date of Report: *The aim of the experiment was to study thediffusion in liquids under shear parallel andperpendicular to the shear gradient.To minimize the smearing of the value of theshear rate relating to the finite beam height atthe disc of the shear apparatus we had toreduce the height of the beam. First theinstrumental setup was optimised without theshear device. Using a wavelength of 5,1 Å andan instrumental resolution of 93 µeV at ascattering angle of 90° already without sheartwo different quasielastic line widths forreflection (45°) and transmission (135°)geometry have been found for a sample oftetradecyl-diametylamine oxide hexanol anddeuterated water (Figure 1). We argue thatthis may originate from a layer structure thathas become anisotropic even without shearingof the sample. An anisotropy in the electricalconductivity has already been reported earlier[1].

Figure 1: Spectrum of TDMAO in reflection andtransmission geometry.

As a second sample we haveinvestigated a 33% (in weight) solution of P85in deuterated water forming different structuresreaching from unimeres to lamellar phasesdepending on temperature. These havealready been explored earlier by small anglescattering [2]. The quasielastic line broadensby increasing the temperature from 18° to70°C reflecting an acceleration of the diffusionon an atomic scale. However on amacroscopic scale the solution becomes muchmore viscose for higher temperatures.

Figure 2: Spectrum of P85 solved in D2O fordifferent temperatures.

Figure 3 shows the same sample in theshear device at a temperature of 25°C in bothtransmission and reflection geometry withoutshear and sheared at about 2500 1/s. Fromthese data it seems that shear does notinfluence diffusion in the investigated time- andlength scale.

Figure 3: Spectra of P85 dissolved in D2O inreflection and transmission geometry withoutshear and sheared at about 2500 1/s.

Further data evaluation is in progress.

[1]. Escaliente et al.: Langmuir 16, 8653(2000).[2] K. Mortensen et al.: J. Phys. : Cond. Matt.8, A103 (1996)

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Instrument V1Alignment of Lipid/Water Systems UsingMagnetic Shear Local Contact

Thomas Hauß

Principal Proposer: John Katsaras, NRC-CNRC, Chalk River Date(s) of Experiment

Experimental Team: John Katsaras, NRC-CNRC, Chalk RiverThomas Gutberlet, HMI, BerlinThomas Hauß, HMI, Berlin

2.-8. 7. 2001


Lipid mixtures composed of short- and long-chainphosphatidylcholines such as, dihexanoylphosphatidylcholine (DHPC) and dimyristoylphosphatidylcholine (DMPC), have been ex-tensively studied [1-4] as potential biomimetic“substrates” capable of aligning a variety ofmacromolecules. These magnetically orientedbilayered micelles or commonly known “bicelles”,align with their bilayer normal, either perpendicularto the applied magnetic field, B (negative ordering),or parallel to B (positive ordering), depending onthe magnetic susceptibility of the bilayer molecules[5-7]. They are believed to achieve diameters ofbetween 100 and 1000 Å, depending on the molarratio (q) of DMPC to DHPC [1].The liquid crystal phase of a DMPC/DHPC mixtureis gel-like and has an intrinsic negative ordering (n^ B) at q of DHPC/ DMPC in the range of 1:2-1:6,water content of 97-60 % w/v and temperature of30~50 oC [2]. At lower temperatures (< 20 oC), themixture is in a low viscosity isotropic phase andcannot be aligned in a magnetic field. It ishypothesized that in this phase, long-chain DMPCmolecules occupy the center of the bicelle diskwhile the short-chain DHPC molecules stabilize thebicelle by coating its edges [1,2,4]. In the negativeordering condition the bilayer is still able to rotatefreely about its axis along B.Based on 2H-NMR experiments it is believed thatrotating (axis of rotation ^ magnetic field) a bicellesystem (2.7:1 mole ratio of DMPC/ DHPC, 70 wt.%50 mM phosphate buffer with 50 mM KCl) in amagnetic field causes the bicelles to align with theirbilayer normals || to the axis of rotation (still ^ tothe magnetic field). In the absence of a rotating axisthe bicelles are aligned with their bilayer normals ^to the applied magnetic field, but in a “powder” likefashion.In the performed experiments the scattering from abicelle system was measured as a function ofrotation of the bicelle sample in the magnetic field(B = 5.5 T). To apply the magnetic field ^ to thebilayer normal, and the axis of rotation ^ to themagnetic field, the horizontal magnet HM1 wasused. Sample temperature was ~308 K, i.e. abovethe isotropic/liquid crystalline phase transition of thesystem.Raising the temperature of the sample, in themagnetic field, resulted in distinct orientations of thebicelles. Strong scattering of the oriented particles

in the plane of the magnetic field was detectedabove 303 K. This scattering was present onlywhen the orientation of the magnetic field, W to E,was such that the magnetic field was perpendicularto the detector. No scattering from oriented bicelleswas detected when the magnetic field was in the Sto N direction.On rotating the sample in the magnetic field (W>E)the scattered intensity fluctuated (Fig. 1). Analysisof the changed intensity with respect to theorientation of the particles and rotation is underway.

Fig.1: Change in scattered intensity during rotation ofDMPC/DHPC/Tm3+ mixture in magnetic field (B 0 5.5 T,axis of rotation ^ to the magnetic field).

[1] R. R.Vold and R. S. Prosser, J. Magn. Reson. B. 113, 267(1996).[2] J. Katsaras, R. L. Donaberger, I. P. Swainson, D. C. Tennant,Z. Tun, R. R. Vold and R. S. Prosser, Phys. Rev. Lett. 78, 899(1997).[3] J. Katsaras, Physica B 241, 1178 (1998).[4] R. S. Prosser, J. S. Hwang and R. R. Vold, Biophys. J., 74,2405 (1998).[5] K. D. Lawson and T. J. Flautt, J. Am. Chem. Soc. 89, 5489(1967).[6] B. J. Forrest and L. W. Reeves, Chemical Reviews 81, 1(1981).[7] J. Seelig, F. Borle and T. A. Cross, Biochim. Biophy. Acta814, 195 (1985).

40 60 80 100

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130

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EXPERIMENTAL REPORT Proposal N° BIO-04-0656

Instrument V4Investigation of Mixed Lipid/SurfactantAggregates in Magnetic Field Local Contact

Armin Hoell

Principal Proposer: Mikael Kiselev, FLNP JINR, Dubna, Russia Date(s) of ExperimentExperimental Team: Mikael Kiselev, FLNP JINR, Dubna, Russia

Thomas Gutberlet, HMI, Berlin, GermanyArmin Hoell, HMI, Berlin, Germany

26.-29. 11. 2001


Orientation of mixed lipid/surfactantaggregates in the magnetic field has beenused to study the different stages ofmorphological transformations in such systemsinitiated via temperature alteration. The systeminvestigated consisted of the phospholipiddimyristoylphosphatidylcholine (DMPC) andthe surfactant dodecyloctaethylenoxide(C12E8) which transform from micelles tovesicles at increasing temperature from 10 to37°C [1]. The last structure before mixedlipid/surfactant aggregates self assemble intovesicles are polymer-like micelles. Theorientation of the polymer-like micellaraggregates in magnetic field was shownpreviously by SANS [2]. In our present experiment we now investigatedthe orientation of the vesicles itself in themagnetic field. Using SANS instrument V4 atBENSC the sequence of transitions ofspherical-like micelles, rod-like micelles,polymer-like micelles and, finally to vesicleswere examined for DMPC/C12E8 mixtureswith 45 mM DMPC and 13 mM C12E8concentration between 10 and 37°C with andwithout magnetic field, H=4 T, using thevertical magnet VM3 at BENSC. Forcomparison the orientation of sphericalunilamellar vesicles of DMPC with medium (50nm) and large (200 nm) diameter wasinvestigated too in the temperature range of 10to 30°C with and without applied magneticfield, H=4 T.Preliminary results of the performedmeasurements indicate the strong orientationeffect of oligolamellar vesicles in the magneticfield, which has a maximum at the temperatureof 37°C (Fig.1). Detailed analysis of the obtained scatteringcurves is in progress.

Fig.1: 2D SANS pattern of 45 mM DMPC/13 mM C12E8mixed self assembled oligolamellar vesicles at 37°Cshowing orientation along magnetic field applied in thevertical direction (top: 0 T, bottom: 4 T).

[1] T. Gutberlet, M. Kiselev, H. Heerklotz, G. Klose,Physica B, 381-383, 276 (2000).[2] M. Kiselev, M. Janich, P. Lesieur, A. Hoell, J.Oberdisse, J. Pepy, A. Kiselev, L. Gapienko, T.Gutberlet, V. Aksenov, Appl. Phys. A, accepted.

131


EXPERIMENTAL REPORT Proposal N° CHE-04-551Instrument V4PS-PEO Micelles as reactors for Metal

Nanoparticles Formation: A SANS Study Local Contact P. Strunz

Principal Proposer: Roberto Triolo, University of Palermo (Italy) Date(s) of ExperimentExperimental Team: Alessandro Triolo, HMI-BENSC

Fabrizio Lo Celso, University of Palermo 13-21-2-2001


Self-assembly character of diblock copolymeroccurs in solvents that are selective respect toone of the two moieties. Above a certaincritical concentration micelles with asolvophobic core, surrounded by a solvophilicshell are then formed. Crucial parameters insuch studies, apart from the different chemicalformulation of the two blocks, are soluteconcentration and temperature. Small angleneutron scattering has provided evidences ofdifferently shaped aggregates and theirstructural evolution along with experimentalcondition, while theoretical models have beenable to describe, when the polydispersity is nothigh, both the internal constitution of themicelles and their shape. The self-assemblingproperties of amphiphilic block copolymers inaqueous solution can be also exploited toobtain metal nanoparticles stable dispersion. SANS measurements were performed on PS-PEO (polystyrene-b-polyethyleneoxide) blockcopolymers aqueous solution (D2O solution) atdifferent concentrations and temperatures. Theblock copolymer had a PS block of Mn = 700and a PEO block of Mn = 2000 (SE720).Furthermore it has been considered the samepolymeric system where Platinum nanoparticles have been previously synthesized inpresence of a small quantity (below its cmc) ofa cationic surfactant, cetylpyridinium chloride(CPC). Metal nanoparticles are expected to belocated in the hybrid micelle system.Experimental data were fitted by using amodified core-shell model. Indeed it has beenconsidered that a fraction of the PEO chain,that constitutes the hydrophilic shell, could foldaround the highly hydrophobic PS core.Figure 1 shows the fits to experimental data forseveral SE720 solutions at T=25 °C. In thisdilute regime, the scattering intensity is clearlydominated by the form factor, although thestructure factor, that contains a hard sphererepulsive term plus an attractive square well,must be taken into account in order to havereasonable fits. Parameters of the best fits aresummarized in Table 1. Structural parameters

show significant variations, as concentrationincreases, in the swelling of the shell and inthe fraction of folded PEO chain. Lowering thepolymer concentration in solution meansessentially slightly smaller aggregates with aless solvated hydrophilic shell and a lowerdegree of PEO folding around the PS core.Data have been collected on the same system(same concentration) containing the dispersedPlatinum metal nanoparticles. UnfortunatelySANS measurements have not revealedconsiderable differences in the scatteringcurves respect to the pure block copolymersolution. This could be an indication that smallangle X-rays scattering would be a suitableoption.

0.02 0.04 0.06 0.08 0.10

0

5

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15

20

d(Q

)/d

(cm

-1)

Q(Å-1)

% w/V 2.20 1.13 0.58 0.11

Fig. 1. SANS data for PS700-PEO2000 solutions inD2O at T=25 °C and different concentrations. Linesrepresent best fits.

Table 1. Structural parameters obtained from fits for SE720solutions of figure 1. Errors are reported in parenthesis.%w/V = block copolymer concentrationAgg = aggregation numberRcs(Å) = micelle’s diameter Shw = numer of water molecules per EO unit in the shell%PEOf = percentage of PEO foldingWfPEO = numer of water molecules per EO unit in the folded PEO

%w/V Agg Rcs(Å) Shw %PEOf WfPEO

2.21 64.2(7) 69.4 14(1) 0.11(1) 1.3(2)1.13 61.9(3) 66.6 12.3(2) 0.057(1) 1.0(3)0.58 62.5(3) 64 9.91(3) 0 00.11 62.6(6) 63.7 9.73(8) 0 0

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EXPERIMENTAL REPORT Proposal N° Bio-04-0631Instrument V4SANS study of the polyelectrolyte layers

structure for hollow capsules Local Contact P.Strunz, A.Hoell

Principal Proposer: E. Donath, Leipzig University, Leipzig,Germany Date(s) of Experiment

Experimental Team: I. Estrela-Lopis, Leipzig University, GermanyS. Leporatti, Leipzig University, GermanyP. Strunz, HMI, Berlin, GermanyA. Hoell, HMI, Berlin, Germany

13.-16.12.2001


Oppositely charged polyelectrolytes (PE) canbe assembled layer-wise on colloidal templates,for example silica. When the silica core isdissolved in HF, hollow polyelectrolyte shellsare obtained. Such hollow capsules may find awide range of applications, e.g. as carriersystems for drug delivery. However, theseapplications require an understanding of thestability and mechanical properties of thecapsule walls which are supposed to be closelyrelated to the polyelectrolyte layer structureand to the core removal process. In the present work free PE layers (hollowcapsules) were compared with the originalsupported PE layers on silica. Beside the coreremoval also the influence of annealing atelevated temperature and of the saltconcentration on the PE shell wall structure(thickness and density) were investigated.Polyelectrolyte hollow shells were fabricatedby templating monodisperse silica particleswith pairs of poly(styrene sulfonate) (PSS) andpoly(allyl amine hydrochloride) (PAH). Theannealing was conducted at 70°C for 40minutes, 2 and 6 hours, respectively.Fig. 1 compares the neutron scattering from 8PE layers before and after core removal. Thescattering vector (Q) of the minimum for freePE layers (indicated by an arrow) is remarkablelarger than that of supported PE layers. Thefitting yielded the thickness before (290 Å) andafter core removal (170 Å). As can be seenfrom Fig. 2 the Q vector of the PE minimumdecreased with the number of PE layers. Adeeper analysis provided a thickness of 22 Åper single layer. It was remarkably independenton the number of layers. The radius of thehollow shell after core dissolution was identicalto that of the template. Thus, for the first timethe wall thickness of hollow capsules was

directly measured in an aqueous environment.The layer appears as a thin, homogeneous anddense structure in comparison with PE layerson the silica template which were swollen. The annealing of the hollow capsules lead to apronounced decrease of the roughness. Thepresence of the NaCl did not influence on thethickness of the PSS/PAH polyelectrolytelayers.

SiO +8 layers of PE in D O

1

Fig.1. Small-angle neutron scattering fromtemplated silica and hollow shells.

0.1 11E-5

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Fig. 2. Small-angle neutron scattering fromhollow shells consisting of 8, 12, and 16 PElayers.

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EXPERIMENTAL REPORT Proposal N° CHE-04-0633Instrument V4New organogels with alkyl-monogluco-

pyranosides Local Contact U. Keiderling

Principal Proposer: Gradzielski, Michael, Universität Bayreuth Date(s) of ExperimentExperimental Team: Hoffmann, Bettina, Universität Bayreuth

Zapf, Amelie, Universität BayreuthPlatz, Gerhard, Universität Bayreuth

31.8.-2.9. 2001

Keiderling, U., TU Darmstadt, HMI BerlinDate of Report: 15. 2. 2002

Pentyl-, hexyl- and heptylmonoglucopyrano-side form organogels in organic solvents in alimited temperature range around 25°C whichdisplay unusual properties. In benzene or tolu-ene temperature dependent colour effects areobserved. In ethyl acetate the gelation startsafter lowering the temperature at a few nuclei.From these nuclei highly ordered and stronglybirefringent spherulites start to grow. Finallythe spherulites fill the entire size of the cells.By SANS measurements in d6-benzene andd8-toluene the behaviour of the systems wasinvestigated as a function of temperature,solvent and concentration. From the analysisof the scattering data it can be concluded thatthe gels are essentially built of cylindrical,branched aggregates as in typical organogels,i. e. a fibrous structure is present [1]. Fig. 1a gives some typical scattering curves forpentyl--D-pyranoside in ethyl acetate at dif-ferent temperatures. At high temperature verylow scattering intensity is observed that is dueto a molecular solution of the pyranoside.Upon lowering the temperature a significantincrease in scattering intensity takes place anda pronounced minimum around q=0.045 Å-1

can be seen. For the more concentratedsample (fig. 1b) a similar scattering pattern isobserved that indicates the presence of rod-like aggregates with a radius of 80-90 Å. Herethe same basic fibrous structures are presentbut it appears that they are more well-definedat the lower concentration. At higherconcentration they are packed more closelytogether as indicated from the shift of the bend(around q=0.02 Å-1) in the scattering curves tolower q. However, it can be noted that now themelting to a monomeric solution does not takeplace at temperatures up to 40 C.In general similar patterns have been observedin the other solvents and the SANS experi-ments allow clearly to distinguish between thestructure less isotropic solution of monomeri-cally dissolved pyranosides and the formationof the highly viscous organogels. The details ofthe fibrous structure of the organogels dependon the solvent, strongly on the type of pyrano-side, and are sensitive to the temperature.

[1] P. Terech, Ber. Burnsenges. Phys. Chem. 102,1630 (1998)

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Fig 1: Scattering curves for Pentyl--D-glucopyranoside / ethylacetate (a: left 0.049 g/ml; b: right 0.114 g/ml) atdifferent temperatures

135


EXPERIMENTAL REPORT Proposal N° CHE-04-0636Instrument V4Formation of silica gels in the presence of

cationic additives and surfactants Local Contact U. Keiderling

Principal Proposer: Markus Meyer1, 1Physikalische Chemie I, Date(s) of ExperimentExperimental Team: Markus Meyer Universität Bayreuth

Dieter Gräbner1 2HMIUwe Keiderling2,3 3TU Darmstadt

26.Aug. – 30.Aug.2001

Date of Report: *

A typical way for structuring silica gels is to usesurfactants as templates. Using a novel Si-precursor(ethylene-glycolester of silicic acid), we canincorporate any water soluble compound in theSiO2-network. In order to avoid syneresis ourgroup adds small amounts of cationic additives tothe Si-precursor. The aim of this study was toinvestigate the influence of the cationic additive onthe structure of the wet silica gel.We did time dependent SANS measurements withdifferent additives in varying concentrations. Figure1 shows the scattering curves of a gel containing 50wt.% Si-precursor and 0.5 wt.% cationic additiveA1 in H2O. The cationic additive causes acorrelation peak which is shifted with time tosmaller q-values. It is likely that the appearance ofthe scattering peak is a consequence of therepulsive interaction between charged clusters. Themean distance of the clusters calculated from qmax(d=2π/qmax) increases from 15.6 to 20.9 nm. Thisresult corresponds to the results of BETmeasurements of the aerogels where we found amaximum in pore size distribution at 13 nm. Using the cationic additive A2 with a longerhydrocarbon chain in comparison to A1 the meandistance of the charged clusters calculated fromqmax is risen to values between 16.7 - 25.4 nm (seefigure 2).The next step was to use a surfactant and a cationicadditive together as a template for the structure ofthe SiO2-network. Figure 3 shows scattering curveswith different concentrations (wt.%) of thesurfactant Sodium dodecylsulfate (SDS). With 1wt.% SDS no micellar correlation peak is seen. Thecalculated distance between the micelles decreasesfrom 6.4 nm at 5 wt.% to 5.6 nm at 10 wt.% SDS.This is simply caused by an increasing number ofmicelles as the concentration rises. The applicationof surfactant and cationic together results in fairlythe same mean distance (5 wt.% SDS + A1: 6.6 nm,10 wt.% SDS +A1: 5.8 nm; see figure 4). Thismeans that the effect of the cationic additive on thestructure is completely neutralized. It can besupposed that the additive is incorporated in themicelles but not incorporated into the SiO2-network.

Fig. 1: Time depending SANS curves for a samplecontaining 50 wt.% Si-precursor and 0.5 wt.% A1

Fig. 2: Time depending SANS curves for a samplecontaining 50 wt.% Si-precursor and 0.5 wt.% A2

Fig. 3: SANS curves for a samples containing 50 wt.%Si-precursor and varying amounts of SDS

Fig. 4: SANS curves for a samples containing 50 wt.%Si-precursor, varying amounts of SDS and 0.5 wt.% A1

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136


EXPERIMENTAL REPORT Proposal N° CHE-04-0653Instrument V4Adsorption of Non-ionic Surfactants onto

Polystyrene Latex Particles Local Contact Amin Hoell

Principal Proposer: Terence Cosgrove, University of Bristol Date(s) of ExperimentExperimental Team: Nicola Nugent, University of Bristol

Andrew Nelson, University of BristolAmin Hoell, BENSC

8th – 11th October 2001

Date of Report: 12th November 2001

AimThe aim of this study was to investigate theinterfacial structure of a layer of non-ionic surfactantadsorbed on polystyrene latex.

Sample Materials and ConditionsThe surfactants under investigation consist of analkyl group and an ethylene oxide oligomer. Thepolystyrene latex particles used were 75%deuterated so that a contrast matched condition(that is, scattering length density of solvent equalsscattering length density of particles) could beachieved. The samples were dispersed in H2O/D2Omixtures and measurements were carried out at25ºC and ambient pressure. Each sample wasmeasured at three geometries in order to maximisethe Q range:

1. Detector Distance=12m, collimation=12m2. Detector Distance=4m, collimation=4m3. Detector Distance=0.975m, collimation=2m

This gave a Q range of 0.004 to 0.37 Å.

Initial ResultsThe contrast match point was determined, bymeasuring the scattering from the “bare” particles ina range of D2O/H2O ratios. The minimum scatteredintensity was found to occur at 16.95% H2O.The scattering from samples of 6 different Lubrolconcentrations (0.25% 0.5%, 0.75% 1%, 1.25%,1.5%) on polystyrene latex particles (radius=45nm,concentration=3.45%w/w) was measured. Thesemeasurements were carried out under the contrastmatched condition described above, in order thatthe scattering from the adsorbed layer alone couldbe observed. See figure1.

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10 Latex + 0.25% LubrolLatex + 0.5% LubrolLatex + 0.75% LubrolLatex + 1% LubrolLatex + 1.25% LubrolLatex + 1.5% Lubrol

Figure 1: Scattering from the adsorbed surfactant layer.

The scattering from the surfactant solutions wasalso measured, at the relevant concentrations, inorder that the scattering from non-adsorbedsurfactant micelles can be accounted for. Seefigure 2.

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Figure 2: Scattering from the micellar solutions.

These experiments were repeated using twodifferent non-ionic surfactants, both of the sameCnEm type.The scattering from the bare latex particles, shownin figure 3, has been analysed by fitting to apolydisperse hard sphere model.

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Figure 3: Scattering from bare particles in D2O.

This gives a particle radius of 44.7nm with a lognormal distribution of 0.08.Full data analysis should reveal adsorbed layerthickness as a function of surfactant concentration,together with information about the size and shapeof the surfactant micelle. It is expected that thestructure of the adsorbed layer (monolayer, bilayeror other) can be elucidated.

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PHY-04-0734LT // brandt // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° PHY-04-734LT

Instrument V4AGGREGATION OF CYCLODEXTRINS INAQUEOUS SOLUTION Local Contact

Dr. Armin Hoell

Principal Proposer: Dr. Bernd Smarsly, MPI of Colloids andInterfaces, 14476 Golm, [email protected] 5. - 6. 8. 2001

Experimental Team: Dr. Armin Hoell, HMI BerlinD Dr. Bernd Smarsly & Dr. Sebastian Polarz,MPI of Colloids and Interfaces *


The aggregation behaviour of cyclodextrines in aqueoussolution was studied by SANS and SAXS.Cyclodextrines (CDs) are cyclic oligosaccharidesconsisting of covalently linked glucose units (6 units =-CD, 7 un. =, 8-un. = -CD). The structure can bedescribed as hollow cylinders with a height of ca. 0.8 nmand a diameter in the range of 1.5 nm – 2 nm. Since themajority of the OH-groups are situated on the exterior ofthe CD molecule, CDs are characterized by a hydrophilicexterior and a hydrophobic interior. In this respect, CDscan be regarded as species with an inherentamphiphilicity. In analogy to the well-known self-aggregation of surfactants and amphiphilic blockcopolymers, the question arises if also CDs show atendency to self-assembly into larger aggregates inaqueous solution as a function of the concentration. Itwas recently shown that CDs, used a template in thepreparation of porous silicas, result in “worm-type”pores[1]. Based on these results, it was concluded thatthe worm-like pore shape originates from aqueous CD-aggregates of similar shape, which indicates a certaintendency of CDs to self-assemble. The self-assembly ofcyclodextrins was previously assumed in several studiesbut was not yet systematically studied in detail bySANS/SAXS to the best of our knowledge. The presenceof CD assemblies was already proposed by Häusler etal.[2], but also mistrusted by Perly et al.[3]

Based on this previous work this study is intended toelucidate the aggregation behaviour of cyclodextrines bysmall-angle scattering techniques. It can be expected thatthe tendency of CD molecules to self-assemble is lowerthan for classical surfactants. Dynamic light scatteringexperiments suggest the existence of larger aggregatedspecies in aqueous solution even below concentrations of1 wt.%. The figure shows the combined SAXS/SANSdata of -methyl-CD in D2O (5 wt.%), which is thelowest concentration still providing usable data.Obviously, the coincidence of both curves proves areasonable data quality. The SANS data were correctedfor the polydispersity in wavelength. The low q region ofthe SANS/SAXS data was evaluated to check for thepresence of larger aggregates. A Guinier analysisprovides a radius of gyration Rg 0.3nm, which isinconsistent with the geometry of a single -CDmolecule. Taking into account the reasonable reliabilityof the data, this significant deviation from Guinier’s lawcould be due to aggregation of the CD units into larger

objects. Moreover, the SANS/SAXS pattern at larger qseems to be inconsistent with the form factor of a singleCD unit. Preliminary evaluations suggest that the dataare in better agreement with an aggregated system ofelongated cylinders with the diameter of CDs. Severalapproaches will be used to fit the SANS/SAXS data witha suitable structure model. We temptatively speculatethat these aggregates form loose, gel-like agglomerates.

In particular, it is ssumed that CDs self-assemble to"worm-type"/cylindrical aggregates because of thehydrophobic interior and the hydrophilic shell whichtogether carry a special kind of amphiphilicity. Amaximum contact between hydrophobic domains amongone another and the hydrophilic domains is given whenthe flat (uncurved) sides of the CD are stacked on top ofeach other. This situation would be energeticallyfavorable and we assume that this should be the drivingforce for the self-assembly.

[1] S. Polarz, B. Smarsly, L. Bronstein, M. Antonietti,Angew. Chem. Intern. Ed. 2001, 40, 23.[2] O. Häusler, C. C. Müller-Goymann, Starch1993, 45, 183.[3] N. Azaroualbellanger, B. Perly, MagneticResonance in Chemistry 1994, 32, 8.

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mailto:[email protected]


EXPERIMENTAL REPORT Proposal N° PHY-03-152Instrument V5Characterization of Trehalose Aqueous Solutions

by Neutron Spin Echo Local Contact C. Pappas

Principal Proposer: C. Branca Dipartimento di Fisica and INFM,Università di Messina, Italy Date(s) of Experiment

Experimental Team: A. Faraone Dipartimento di Fisica and INFM,A. Mangione Università di Messina, ItalyC. Pappas Hahn Meitner Institut, BENSC (NI),A. Triolo Berlin, Germany

11-18/06/2001


In order to get a better understanding on thecryoprotective action of trehalose, a naturally-occurringglass-forming disaccharide[1], we have investigated thedynamics of the trehalose/water system on the nano andpicoseconds scale by means of Neutron Spin Echo(NSE) spectroscopy. NSE measurements have beencarried out using the spectrometer SPAN at BENSC withan incident wavelength of 6.5 Å and for two Q values,Q=0.6 Å–1 and Q=1.0 Å–1. Pure trehalose samples werepurchased from Aldrich-Chemie. The solutions at amolar fraction =0.05, =nd/nd+nw, being nd and nw thedisaccharide and water mole numbers, respectively, wereprepared by weight using double distilled deionizedwater. We measured spectra at different temperaturesranging from 275 K to 354 K. Resolution wasdetermined from a vanadium reference sample.

Results and DiscussionFig 1 presents, on a semilog scale, the results for thenormalized intermediate scattering functions,S(Q,t)/S(Q,0), at Q=0.6 Å–1 at four temperature values.The continuous lines correspond to the best fit of theexperimental data according to a distribution ofcorrelation times by means of the Kolrausch-Williams-Watts (KWW) function: S(Q,t)/S(Q,0)=A0+A1exp[-(t/kww)], where A0 corresponds to the Elastic IncoherentStructure Factor (EISF). The fitting procedure givescharacteristic relaxation times ranging from 0.21 ns to0.05 ns by increasing temperature from 275 K to 354 K,while keeps almost constant (=0.90). The obtained values reveal a deviation from the Arrhenius behaviourat the lowest temperature which indicates a markedincrease of activation energy[2]. Such a peculiar featureis also reflected in the A0 parameter temperaturebehaviour, see Fig 2. Evidence of confinement effectscomes from previous QENS measurements[3],[4] ontrehalose/water solutions at T=323 K and 333 K. TheEISF Q-dependence has been interpreted in terms ofhighly damped reorientation fluctuations of the twoglucose rings around the glycosidic bond. Furthermore,the temperature dependence of EISF evaluated fromMIBEMOL data[5] at temperatures around the glasstransition, has evidenced a dynamical transition fromharmonic to anharmonic regimes at TTg. In continuingour exploration of the relations among dynamics,stability and biological effectiveness of trehalose, theresults obtained in the present work for the and A0values at temperatures well above the glass transition,

evidence an important dynamical transition with arelevant decrease of rigidity at relatively hightemperatures (T290 K). The increasing rigidity of thesystem as the temperature decreases, implies a lowerstructural sensitivity to temperature changes which canaccount for the bioprotective action of trehalose. Furtherstudies on sucrose, maltose and glycerol water mixturesare actually in progress.

Fig 1. NSE spectra at Q=0.6 Å–1 at differenttemperatures. The continuous lines are the results of thefitting procedure.

Fig 2 Temperature behaviour of the A0 parameter.

References[1] J.H. Crowe et al., Annu. Rev. Physiol., 60, 73 (1998).[2] C. Branca et al, Applied Physics A, accepted.[3] S. Magazu', et al., J. Chem. Phys. 105, 1851, (2001)[4] S Magazu’, et al., J.Chem. Phys.,115, 3281, (2001)[5] C. Branca, et al. Phys. Rev. B, 64, 224204, (2001).

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EXPERIMENTAL REPORT Proposal N° PHY-03-174Instrument SPANCoherent Contribution in Liquid Quinoline as a

Function of Temperature Local Contact Dr Pappas

Principal Proposer: Dr David Martin, Rutherford Appleton Lab. Feb 16 – Mar 5, 2001Experimental Team: D. Martin, C. Pappas


Many organic glass forming liquids show thermalanomalies at temperatures within their normal liquidphase. These anomalies have been revealed by severalmacroscopic measurements and are at odds withstandard phenomenological approximations.

Clear anomalies have been found in several macroscopicproperties as the heat capacity, NMR relaxation timesand magnetic susceptibility measurements [1].Remarkably, these anomalies could not be found in theclosely related chemical analog isoquinoline, pointing toa microscopic origin of the measured behaviour.

In particular, the saturated heat capacity and NMR spinrelaxation times measurements performed by Jalabert etal, show a discontinuity in the slope of their temperaturedependence around 290 K [1]. On the other hand,neutron quasielastic measurements have been performedto assess whether the observed macroscopic anomaliescould be traced to microscopic scales [2]. A stronginelastic background which shows a marked wave-vectordependence was observed at the same temperature as theprevious macroscopic observations. Whilst the formerwas interpreted as signature of the presence of two typesof fluids in the liquid, the latter pointed to the interactionof shear excitations and reorientational motions.

The purpose of our experiment was to clarify theseobservations by measuring the temperature dependenceof the coherent contribution to the scattering as the liquidpasses through the transition temperature. By measuringthe dynamical structure factor using polarisationanalysis, a clear picture of the coherent contributioncould be obtained if the liquid went through the expectedchange in slope. According to the references, this changein slope is only observed with extremely purifiedsamples and very slow rate of heating/cooling.

We measured below and above the observed transitiontemperature: 275, 283, 290, 299 and 305K in order tocharacterize the evolution of the collective and single-particle dynamics.

No significant difference was observed in the behaviourof the spectra below and above 290K. More likelyexplanation is the presence of more than ideal impuritiesin the sample, although we cannot discard the need of amore careful data analysis, including an improvedversion of the multiple scattering corrections. Work isunder way in this direction.

References

[1] D.Jalabert et al, Europhysics Letters, 15 (4), pp. 435-440 (1991).

[2] F.J. Bermejo et al, Physical Review E, 48, (4), pp.2766-2775 (1993).

140


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EXPERIMENTAL REPORT Proposal N° MAT-04-609Instrument V6Studies on the SAM/Water Interphase for Films

with Different Protein Resistance Local Contact R. Steitz

Principal Proposer: M. Grunze, Universität Heidelberg Date(s) of ExperimentExperimental Team: D. Schwendel, Universität Heidelberg

R. Dahint, Universität HeidelbergT. Hayashi, Universität Heidelberg

Feb 26 – March 2, 2001June 15 – 19, 2001


Background: Infrared spectroscopy (IR) measurementshave demonstrated that for alkanethiolate self-assembledmonolayers (SAMs) containing oligo(ethylene glycol)(OEG) endgroups, the ability to resist non-specific andirreversible protein adsorption from biological media isnot only dependent on the conformation of the EGgroups but also on the length of the terminal alkyl chain.While the helical or amorphous methoxy tri(ethyleneglycol) (EG3-OMe) terminated films are resistant againstirreversible protein adsorption, the more hydrophobic,but equally conformed ethoxy terminated SAM (EG3-OEt) shows remarkable adsorption of proteins [1].Besides that, IR experiments have revealed that EG3-OMe/Au loses its protein resistant properties attemperatures below ~ 15 °C [2].Theoretical studies predict that for a helicalconformation of the SAMs, a thin layer of water exists atthe water/SAM/solid interphase with reduced densitycompared to bulk water [3, 4]. This interphase waterlayer with reduced density is suspected to be the physicalcause of the protein resistant properties of helical OEGSAMs, as it effectively prevents the biomolecules fromreaching the surface. A more detailed description of thebackground of the study and the theoretical model isfound in ref. [4].Neutron reflectivity measurements performed at theHahn-Meitner-Institut are focused on probing thestructure of the water/SAM/solid interphase for SAMswith different endgroups and different degrees of proteinresistance. Additionally, the interphase behavior of EG3-OMe/Au in contact with D2O has been investigated at 25and 5 °C.Neutron reflectivity measurements: Previousexperiments performed at the Hahn-Meitner-Institut in1999 and 2000 already indicated the presence of a thinlayer of density reduced interfacial water for EG3-OMe/Au [5, 6]. Fig. 1 shows the neutron reflectivity profile of EG3-OEt/Au against D2O. Like in former experiments carriedout for EG3-OMe/Au [5, 6], the data cannot besatisfactorily fitted with a model assuming that bulkwater directly contacts the SAM (dashed line). In thecase of EG3-OEt/Au measured against D2O, two boxesof interphase water (IW) were added between the SAMand the bulk water phase to obtain good correlation(dotted line). The thickness of the IW layers was about40 Å each with a density of 78% and 90% compared tobulk D2O, respectively.Fig. 2 shows the neutron reflectivity data for EG3-OMe/Au against D2O at 25 and 5 °C. Although the

ability of EG3-OMe/Au to repel protein from aqueoussolution vanishes at 5 °C [2], the structure of theSAM/water interphase does not change. Both data setscould be fitted with an IW layer of 52 Å and a density of87% yielding excellent correlation.

Fig. 1: Neutron reflectivity profile for EG3-OEt/Auagainst D2O. Models assuming water in direct contactwith the SAM (dashed), 1 additional IW layer of 41 Å witha density of 85% (dash dot), and 2 additional IW layers of42 and 39 Å with a density of 78 and 90% (dotted).

Fig. 2: Neutron reflectivity profile for EG3-OMe/Auagainst D2O at 25 °C (solid dots) and 5 °C (open dots).

References:[1] S. Herrwerth et al., in preparation.[2] D. Schwendel et al., Langmuir (2001), 17, 5717-5720.[3] R.L.C. Wang et al., J. Phys. Chem. B, 101 (1997) 9767.[4] A.J. Pertsin, M. Grunze, Langmuir, 16 (2000), 8829-8841.[5] D. Schwendel et al., BENSC, Exp. Reports (1999) 249-252.[6] D. Schwendel et al., BENSC, Exp. Reports (2000)145-147.

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EXPERIMENTAL REPORT Proposal N° *MAT-04-0661Instrument *V6Studies on the SAM/Water Interphase for

Monolayer Films of Different Hydrophilicity Local Contact *R. Steitz

Principal Proposer: M. Grunze, Universität Heidelberg Date(s) of ExperimentExperimental Team: D. Schwendel, Universität Heidelberg

R. Dahint, Universität HeidelbergT. Hayashi, Universität Heidelberg

*Nov. 13 – 19, 2001

Date of Report: *January 11, 2002

Background: As already reported in the first part,Herrwerth et al. found different degrees of proteinresistance for amorphously conformed methoxy andethoxy terminated tri(ethylene glycol) alkanethiolateself-assembled monolayers on Au (EG3-OMe and EG3-OEt) [1]. To obtain a better understanding of theinfluence of the hydrophilicity on the structure of theSAM/water interphase, neutron reflectivity experimentshave been performed on methyl terminatedundecanethiol on Au (C18/Au) with an advancing watercontact angle, , of ~110° and OH-terminated 11-mercapto-1-undecanol on Au (C11OH/Au) with ~28°.Fig. 1 shows a simulation of C18/Au and C11OH/Auagainst D2O assuming both SAMs in direct contact withthe bulk water phase.

Fig. 1: Simulation of the neutron reflectivity profile forC18/Au (solid line) and C11OH/Au (dotted line) againstD2O assuming both SAMs in direct contact with the bulkwater phase. Neutron reflectivity measurements: Experimentalstudies on these systems performed at the Hahn-Meitner-Institut indicated a significantly different structure of theSAM/water interphase. In order to eliminate differencesin the spectra caused by variations in the thickness androughness parameters of the Au/Cr/quartz substrate, C18had been removed after the first measurement by UVradiation in a highly concentrated O2 atmosphere [2].Afterwards, C11OH was prepared on the Au surface ofthe same substrate. As demonstrated in Fig. 2, the measured neutronreflectivity data significantly differ from the simulationsof Fig. 1. As the simulation only accounts for differencesin the thickness and scattering length densities of the twoSAMs, the deviation in the experimental profiles has tobe attributed to different structures of the SAM/water

Fig. 2: Neutron reflectivity profiles of C18/Au (solid dots)and C11OH/Au (open dots) against D2O.

interphase. Thus, direct bulk water/SAM contact can beexcluded as also confirmed by comparison to variousmodels. C18/Au could be fitted with excellent agreementassuming two layers of reduced density between theSAM and the bulk water phase, the first with a thicknessof 21 Å and a density of 9% and the second with athickness of 48 Å and a density of 88% compared tobulk D2O. This very low density in the first interphasewater (IW) layer might be related to the formation ofnanoscopic gas bubbles at the hydrophobic surface,which has already been observed in AFM measurements[3-5]. Profiles obtained with degassed and non-degassedD2O could not be distinguished. Experiments usingSAMs, which have been prepared with minimal aircontact [3], are in progress.C11OH/Au against D2O revealed an ambivalentinterpretation of the interphase behavior. Fits of similarquality could be obtained for a model involving two IWlayers of higher density (127 Å, 107% and 43 Å, 103%)and another containing two IW layers of lower density(25 Å, 59% and 48 Å, 88%) compared to the density ofbulk D2O.

References:[1] S. Herrwerth, W. Eck. M. Grunze, in preparation.[2] C.G. Worley nad R.W. Linton, J. Vac. Sci. Technol. A,(1995), 13, 2281-2284; D.W. Moon et al., J. Vac. Sci. Technol.A, (1999), 17, 150-154.[3] N. Ishida, M. Sakamoto, M. Miyahara, And K.Higashitani, Langmuir (2000), 16, 5681-5687.[4] T. Ederth, B. Liedberg, Langmuir, (2000), 16, 2177.[5] J.W.G. Tyrell and P. Attard, Phys. Rev. Lett., 87, 17.

142

EXPERIMENTAL REPORT

Critical Adsorption in Thin Wetting Films of aC6H14/C6F14 Mixture


Instrument V6

Local Contact

R. Steitz


2. 3. - 6. 3. 2001

Principal Proposer: Werner Press, Universitat Kiel

Experimental Team: Wolfgang Prange, Universitat KielRoland Steitz, TU Berlin / HMI Berlin


Introduction

Thin liquid wetting films offer the possibilityto study the mixing behaviour of binary liquidsunder confinement in the direction perpendicu-lar to the substrate. We have conducted neu-tron reflectivity measurements of liquid films ofa mixture of hexane (C6H14) and perfluorohex-ane (C6F14). The wetting films were preparedon the smooth surface of a silicon crystal, whichwas covered by a native oxide layer. The aimof the experiment was to extend the knowledgeabout the mixing behaviour of very thin films [1]to films with thicknesses higher than 500 A.

The mixing behaviour of two liquids having amixing gap is especially interesting in the caseof critical adsorption, where universal criticalbehavior is exhibited. Theory and experimentshow that inside the bulk liquid the concentra-tion is modified at a wall [2,3,4].

The bulk system of the binary mixtureC6H14/C6F14 is completely miscible above theupper critical solution temperature Tc ≈ 295K[5]. We have examined binary films at tempera-tures in the range from T = 298K to 308K, cor-responding to the one-phase regime of the bulksystem.


From neutron reflectivity, the scattering lengthprofile can be determined. Due to the scatter-ing contrast between the alkane and the perflu-oroalkane, the local scattering length density ofthe liquid film directly relates to the local con-centration of the perfluorinated component.

Figure 1 shows the measured reflectivity data.A first analysis reveals that the film thickness isindeed in the range from 500 A to 600 A (the fitsare not displayed). The high roughness of the

film surface makes the analysis difficult, how-ever. Therefore, concentration profiles of thefilms could not be determined, yet.

Figure 1: Reflected intensity for different tem-peratures of the sample. qz is the vertical wavevector transfer.

References

[1] W. Prange, T. Kurbjuhn, M. Tolan, W.Press, J. Phys.: Condens. Mat. 13, 4957 (2001)

[2] G. Floter, S. Dietrich, Z. Phys. B 97, 213(1995)

[3] A.J. Liu, M.E. Fisher, Phys. Rev. A 40,7202 (1989)

[4] J. Bowers, E. Manzanares-Papayanopoulos,I.A. McLure, R. Cubitt, J. Phys.: Condens.Matter 10, 8173 (1998)

[5] B. R. McClain, M. Yoon, J. D. Litster, andS. G. J. Mochrie, Eur. Phys. J. B 10, 45 (1999)

143

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EXPERIMENTAL REPORT Proposal N° CHE–04–580LTInstrument V4Structure Characterization of Polybutadiene-b-

Poly(ethyleneoxide) Micelles in the Presence of the AnionicCosurfactant SDS Local Contact

A. Brandt

Principal Proposer: A. Nordskog, TU Berlin Date(s) of ExperimentExperimental Team: A. Nordskog, TU Berlin

A. Brandt, HMIU. Keiderling, TU Darmstadt, HMI

5.-7.03.2001


The block copolymer (BCP) polybutadiene-b-poly(ethyleneoxide) with a block length ratio of 0.8-1forms micelles in aqueous solutions [1]. Addition of asurfactant of low molecular weight to theblockcopolymer micelles should lead to a highernatural curvature in the internal interface and to achange in the overall structure. It has been shown thatupon addition of the cationic surfactant dodecyl-trimethylammoniumbromide (C12TAB) to PB37-PEO53a transition into spherical micelles takes place [2]. In this case we investigate an aqueous solution of theBCP PB125-PEO155 with different amounts of theanionic surfactant sodiumdodecylsulphate (SDS).Light scattering experiments indicate that the shape ofthe aggregates remains cylindrical after addition of thesurfactant. For the SANS experiments we prepared samples ofPB125-PEO155 and SDS with molar ratios ofN(BCP)/N(surfactant) = rm of 65, 100, 150 and 200 inD2O. We also prepared the same samples usingdeuterated SDS and samples containing the sameamounts of SDS per weight, but without BCP.

0.1 10.01

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100

1000

Fig. 1

rm 0 65 100 150 200

I [cm

-1]

q [nm-1]

Figure 1 shows the scattering curves of the BCP withhydrogenated SDS (open symbols) and of solutionsconrtaining the same amounts of SDS in D2O (solidsymbols). We see a broad peak at high q-values,probably caused by a structure factor of SDS. In bothcases the corresponding curves are identical at q-values higher than 0.7 nm-1, which means that thestructure factor is only dependent on the amount ofSDS and not its location. Compared to the scatteringcurve of the pure polymer (line), we see a shifting ofthe minimum to the right, which can also be seen inthe case of deuterated SDS (Figure 2).

Using deuterated SDS it is possible to study thestructure of the aggregates without the disturbingcontribution of the SDS. These scattering curves areshown in figure 2.

The scattering curves were analyzed using softwarefrom Glatter (Figure 2). We see a shifting of theminimum to higher q-values upon addition of SDS tothe pure polymer solution. At all amounts of SDS onlysmall changes can be observed. The resulting p(r)-functions are shown in Figure 3. From the purepolymer solution to a sample with a surfactant amountof rm=65 a big decrease in the dimension from 90 to40 nm can be observed. A further increase of theSDS-amount to rm=200 only leads to a smallreduction. The shape of the scattering curves and thep(r)-functions indicate that we still have cylindricalaggregates although their dimension decreasesradically upon addition of SDS.

References[1] S. Förster, E. Krämer, Macromolecules 32, 2783-2785 (1999).[2] H. Egger, A. Nordskog, P. Lang, Macromol.Symp. 162, 291-306 (2000).

0.1 11E-3

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Fig. 2

rm 0 65 100 150 200

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-1]

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r (nm)

144


EXPERIMENTAL REPORT Proposal N° PHY-04-607Instrument V6Structure of Thermosensitive Polymer Films at

the Solid/Liquid Interface Local Contact R. Steitz

Principal Proposer: Regine v. Klitzing, TU Berlin Date(s) of ExperimentExperimental Team: Regine v. Klitzing, TU Berlin

Roland Steitz, TU Berlin and HMI 23.-27.03. 2001


In recent years, colloidal microgel particles attractmuch interest because of their fast response toexternal stimuli. The control of their swelling/de-swelling behavior in solvents is of major importancefor applications in the fields of engineering and bio-technology. The design of devices often requiresimplementation of a sensing material in coatings,adsorbed to solid substrates. One of the potentialcandidates is Poly-N-Isopropylacrylamide (PNIPA)as PNIPA macro- and microgels show a tempera-ture induced de-swelling in water at 35°C /1/.We report experiments, which focused on confine-ment effects on the swelling behavior of PNIPA. Forthis purpose we assembled ultrathin multilayers byalternate adsorption of cationic and anionic thermo-sensitive polyelectrolytes from aqueous solution onsilicon single crystals (80 x 50 x 15 mm3), pre-coated with a layer of branched polyethyleneimine.The structure of the solvent-swollen films wasinvestigated by neutron reflectometry as a functionof sample temperature. Three films were prepared:film 26, assembled from two copolymers ofopposite charge, both of which contained NIPAmonomers, PSS-b-PNIPA, and P-(DADMAC-stat-NIPA); film 27, built from a block-copolymercarrying NIPA (PSS-PNIPA) and the homo-polymerPDADMAC and film 28, the reference, consistingsolely of PSS and PDADAMC.The multilayer-coated substrates served as top of aflow cell filled with D2O. The cell was water-thermostated to the respective temperature. Theincident neutron beam impinged on the solid/liquidinterface from the solid side. Reflectivity spectrawere recorded in single /2 steps with one runconsuming ca. 8h of beamtime.All films showed tremendous swelling whenexposed to liquid D2O. The swelling scaled with theamount of NIPA present in the film (see Table 1).Although all films were prepared the same way (7dipping cycles) their thickness was found to bestrongly dependent on the polyelectrolytes used.The thickest film was obtained from the combi-nation PSS-b-PNIPA/PDADMAC. The pair PSS-b-NIPA)/P-(DADMAC-stat-NIPA) yielded the thinnestfilm. All wet films responded to elevated tempera-ture. Two effects were pinned: (i) film shrinkage(from the shift of the fringe positions in the neutronreflectivity spectra towards high Q), and (ii)changes in the internal film structure (from the dropin reflectivity in the Q-range from 0.02 to 0.12 Å-1,see Fig.1). Subsequent neutron reflectivity mea-

surements conducted on film 27 and 28 aftercooling from 60°C to 20°C showed that thestructural changes were irreversible. The availablebeamtime did not allow completion of the tempera-ture cycle for film 26 (the reflectivity spectrum at20°C after heating is missing). The conducted experiments proof a strong influ-ence of the geometrical confinement on the thermalbehavior of PNIPA: While a block of PNIPA (film26) still shrinks by a factor of ~ 1.6, which is veryclose to the factor of 1.8 found for Polystyrene latexparticles with PNIPA shell /2/, there is no specificshrinkage of individual slices of PNIPA separatedby thermo-insensitive PDADMAC (see Table 1).

0.00 0.04 0.08 0.1210-5

10-4

10-3

10-2

10-1

100

20°C 60°C 20°C

Ref

lect

ivity

Q [Å-1]

Fig. 1: Subsequent neutron reflectivity curves fromfilm 27 at the solid-liquid interface as a function ofsample temperature (from top to bottom).

Tab. 1: Film thickness d in Å against air and D2Odry

x-rayswet

neutronsswelling shrinkage

214 (b) 1.62Film 26 132 136 (e) 1.57

549 (b)Film 27 363 509 (a) 1.40 1.08

440 (b)Film 28 303 379 (a) 1.25 1.16Swelling = dwet/ddry; shrinkage = d(b)/d(e) or (a); (b) =before, (a) = after heating cycle, (e) = 60°C

/1/ K. Kratz, T. Hellweg, W. Eimer, Ber. Bunsenges.Phys. Chem. 1998, 102, 1603; /2/ N. Dingenouts, C. Nordhausen, M. Ballauff,Macromolecules 1998, 31, 8912

145


EXPERIMENTAL REPORT Proposal N° MAT-04-662Instrument V6Diblock Copolymers at the Water SurfaceLocal Contact Roland Steitz

Principal Proposer: Christiane A. Helm, Uni Greifswald Date(s) of ExperimentExperimental Team: Alexander Wesemann, Uni Greifswald

Heiko Ahrens, Uni Greifswald 9.-13.5.2001 (04-605)30.7.-5.8.2001

Date of Report: Jan 30, 2002

Diblock copolymers consisting of a hydrophobic and ahydrophilic group were investigated at the air/waterinterface. As the hydrophobic anchoring group servedfluid poly (etylethylene) (PEE), which guarantees thatthe hydrophilic blocks are in equilibrium. Furthermore,the PEE-thickness was verified with X-ray reflecto-metry. The solubilized polymers are anchored at theair/water interface. In the last year, we focussed onPEE202PEO360. Surface coatings with ethylene oxide(EO) polymers have encountered tremendous interestbecause of many potential medical applications toprepare biocompatible surfaces and drug carriers.Originally, it was assumed that PEO lays flat on thesurface, then it desorbs.

Fig. 1: Neutron reflectivitycurves (points) normalized onthe Fresnel reflectivity togetherwith fits (lines) ofPEE202PEO360 on the D2Osurface at molecular areasindicated in the isotherm in theinset (1 is the desorptiontransition of PEO). The highfrequency oscillations are due tothe PEO-brushes. Theoscillations with low frequencyat large Qz are due to the PEE-anchoring group. Note that curveA was measured aftercompressing the monolayer very

quickly, which lead to four instead of two-three PEO interferenceminima.

PEE202PEO360 block copolymers were investigated at theair/water surface at different grafting densities, theobtained neutron reflectivity curves are depicted in Fig.1. In contrast to previous findings1-3 , interference of thePEE with its negative scattering length density can beobserved, cf. Fig. 2 (left). Its thickness and density arethe same as observed with X-ray reflectivity, cf. Fig.2(right)4,5 . The main difference between our current andearlier work is the fluidity of the PEE-group. Due to ourinterest in equilibrium polymer conformation we wantedto have a fluid anchoring group, not a glassy one asdescribed before1 9. We would like to emphasize that themain features, the PEE-melt and the PEO-brushes werealso observed with a 45%/55% D2O/H2O mixture andanother PEE-PEO block copolymer on D2O,PEE432PEO484.While the brush profiles correspond roughly to those ofanchored adsorbing polymers (cf. Fig. 2 left), we findthat slow compression is necessary, with three to four 8-

10 hour breaks to achieve the rounded profiles shown inFig.2. On fast compression (0.9 Å2/s)) four instead oftwo or three interference minima are observed, leadingto a box-like brush profile (curve A in Figs 1 and 2, left).If we compress directly to high pressures, and wait therefor about 20 hours, no relaxation occurs. Even if weexpand and recompress, no relaxation is found.

Fig. 2: Left: Scattering length density profiles corresponding to thefitted reflectivity curves shown in Fig. 1. Note that the quicklycompressed curve A exhibits a much sharper PEO/water interface thenthe slowly decaying equilibrium density profiles. Right: PEE thicknessas obtained from X-ray (black) and neutron (red) reflectivity. Thestraight line is calculated assuming the same mass density for the nm-thick PEE-layer as known from the bulk phase, which necessitated arecalibration of the molecular area by a factor of 1.5.

Fig. 3 gives an overview of the PEO-thickness asobserved during monolayer compression. Even thoughthere is due to the history dependence of the thickness alot of scatter, the increased thickness observed at lowtemperatures is very clear. We have indications thatpolymer shrinking occurs on temperature increase, yetthe results are ambiguous. We need to improve thetemperature isolation.

Fig. 3: The PEO layerthickness of PEE202-PEO360.Experiments symbolized withspheres were performed atroom temperature, thosesymbolized with squares at6oC. Spheres with a black rimrefer to a sudden increase ingrafting density, whichappears to lead to a more box-

like profile and an apparent larger thickness.

Now, we are trying to apply volume fraction profiles ofthe PEO-brushes which are consistent both with x-rayand neutron results. We find strong indications ofdomain formation.

Literature1) B.H. Bijsterbosch et al. Langmuir 1995, 11, 4467.2) M.S. Kent et al. J. Chem. Phys. 1995, 103, 2320.3) E. P. K. Currie et al. Macromolecules 1999, 32, 487.4) H. Ahrens et al. Phys. Rev. Lett. 1998, 81, 4172.5) H. Baltes et al. Macromolecules 1997, 30, 6633.

a

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D2O 30% D2O D2O D2O 54% D2O 6°C

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146

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EXPERIMENTAL REPORT Proposal N° EFInstrument V6Adsorption of C8E4 to the polymer-

solution interface Local ContactR. Steitz

Principal Proposer: R. Steitz, G.H. Findenegg, TU Berlin Date(s) of ExperimentExperimental Team: Sebastian Schemmel, TU Berlin

Roland Steitz, TU Berlin 21.-25.02.200117.-22.07.2001


The adsorption of surfactants to polymersurfaces and its influence on the wetting behaviorof these surfaces is still not well understood,despite the ubiquitous practical importance in dailylive. Surfactants are also used to tune theproperties of polymeric colloidal dispersions, and itis believed that the resulting changes of themacroscopic behavior of the dispersions are relatedto the structure of the surfactant layer adsorbed atthe colloidal particles. For these reasons it isdesirable to characterize surfactant adsorption atthe polymer/solution interface on a microscopiclevel. Neutron reflectometry is particularly wellsuited to address this problem: Single crystallinesolid substrates such as silicon are transparent toneutrons and, the scattered neutrons respond tothe scattering length density variations, Nb(z) onthe molecular scale.

We have studied the adsorption of the nonionicsurfactant C8E4 (Fluka) from solutions in D2O todeuterated polymethylmethacrylate (d-PMMA, 34.5kDa, PSS Mainz) and deuterated polystyrene (d-PS, 65.4 kDa, PSS Mainz) surfaces in theconcentration range from 0.1 to 1.5 CMC (CMC =critical micelle concentration). Polymer films ofuniform thickness (260 and 430 Å) were preparedon silicon blocks by spin-coating (3500 rpm) fromtoluene solution (6 mg/ml) and subsequentannealing at 120 °C for 12h. The polymer coatedsilicon blocks of dimensions 80 mm x 50 mm x 15mm served as top of a home-made sample cell forneutron reflectivity studies of solid/liquid interfaces.It consists of a PTFE trough of inner dimensions 72mm x 42 mm x 3 mm with stainless steel inlet andoutlet tubes for the fluid mounted in oppositecorners of the trough. It was sealed with a Viton O-ring against the silicon block. The whole sample cellexcept the beam entrance and exit sides (50 mm x15 mm) of the silicon block was imbedded in awater thermostated aluminum cage which allowedfor temperature control with a PT100 sensor placedin the base of the PTFE trough. All reflectivitymeasurements were made at a sample temperatureof 25ºC (ca. 15 K below the lower critical solutiontemperature of the C8E4 + D2O system).

The contrast scenario of the neutron reflectivityexperiments was chosen such as to highlight theprotonated surfactant layers. The overall finding isthat C8E4 strongly adsorbs to both, PS and PMMAsurfaces: Layers with a thickness of ca. 25 Å withsurfactant volume fractions S ≥ 0.5 were observed

above a bulk surfactant concentration of theaqueous subphase as low as 0.33 CMC. The measurements revealed that the surfactant isnot penetrating the polymer coatings. However,strong indications were found for a surfactantmediated displacement of d-PS coatings with holesfrom the silicon substrates (see Fig. 1).

0.00 0.05 0.10 0.1510-6

10-5

10-4

10-3

10-2

10-1

100

Ref

lect

ivity

Q [Å-1]

0 200 400 600

2

4

6

SiOx

fluidd-PS

Si

ad1

ad2

z [Å]

Nb*

106 [Å

-2]

Fig. 1: Neutron reflectivity from a d-PS coatingagainst a solution of C8E4 in D2O (cS=0.33 CMC).The dashed line shows the best fit to theexperimental data with one surfactant adsorptionlayer, ad2, at the outer surface of the polymercoating against the liquid (see Inset). The solid lineis the best fit with two adsorption layers, ad2, at thesurface of the polymer coating against the bulksolution and ad1 at the inner surface of the coatingagainst the silicon substrate. Note that the modelwith two adsorption layers yields a perfect match,while the model with one adsorption layer does notfit the experimental data in the Q-range from 0.05 to0.12 Å-1. Also, the extracted scattering lengthdensity of the d-PS coating is reduced beyond thephysically plausible limit in the latter case: ascattering length density of 5.7·10-6 Å-2 correspondsto a volume fraction of protonated surfactant insidethe coating of 12%. This is in strong disagreementwith the volume fraction of holes of 8% found fromcalibration measurements of this coating againstH2O and D2O beforehand. It is these holes whichare assumed to make the inner surface of the d-PScoating against the silicon substrate accessible tothe surfactant.

147


EXPERIMENTAL REPORT Proposal N° EFInstrument V6Boundary layer structure of an iBA + D2O mixture at

the hydrophilic silica surfaceLocal Contact Roland Steitz

Principal Proposer: R. Steitz, G.H. Findenegg, TU Berlin Date(s) of ExperimentExperimental Team: R. Steitz, TU Berlin

S. Schemmel, TU Berlin 15.-21.10.2001


The binary liquid system iBA (iso-butyric acid)plus D2O exhibits a lower miscibility gap asshown in the temperature – composition phasediagram of Fig. 1. For a weight fraction, w, ofiBA of 0.54 the one-phase liquid mixture (T >Tdem) separates into an iBA-rich phase and aD2O-rich -phase at a demixing temperature,Tdem, of 40 °C.

0.2 0.3 0.4 0.5 0.632

34

36

38

40

42

44

46

48

50

two phaseregion

one phaseregion

tem

pera

ture

[°C

]

w(iBA/D2O)

Fig.1: Phase diagram of the binary liquidmixture iBA (iso-butyric acid) plus D2O intemperature – composition space

We have studied adsorption effects occurringat the planar interface between hydrophilicsilica and this binary mixture as a function oftemperature by neutron reflectometry. After displacement of pure D2O by the binaryliquid mixture iBA/D2O (w=0.54) a pronouncedshift in the position of the total reflection edge(TRE) towards low momentum transfer, Q, wasrecorded (Fig.2). This left-shift reflects thelower scattering length density of the mixture(3·10-6 Å-2) in its one-phase region comparedwith the scattering length density of pure D2O(6.37·10-6 Å-2). Upon approaching Tdem fromhigher temperatures a shift of the TRE of thespectra towards high Q was observed. Thisshift may be attributed to the development of aD2O enriched incipient wetting layer at thesilica-solution interface.

In the close vicinity of Tdem a double (reflection)edge appeared in the reflectivity curves. Thisdouble edge was also present at temperaturesbelow Tdem, i.e. in the two-phase region of thebulk mixture, where the upper (iBA-rich) bulkphase is in contact with the silica surface, andthe water-rich phase at the bottom.

0.00 0.01 0.02 0.0310-3

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D2O 60.9°C 46.1°C 42.8°C 41.9°C 41.0°C 40.9°C 34.2°C

R

efle

ctiv

ity

Q [Å-1]

Fig. 2: Neutron reflectivity curves from theinterface of a silicon single crystal coated withits native, hydrophilic silicon oxide layeragainst pure D2O (top) and against a mixtureof iBA/D2O (w=0.54) at various sampletemperatures as indicated in the legend(subsequent curves, top to bottom).

In the two-phase region the spectra exhibit astrong time dependence of the reflectivity inthe low Q region (not shown in Fig. 2). Theappearance of the double reflection edge hintsat a iBA-rich layer, possibly due to incompletewetting of the substrate by the water-richphase. A detailed analysis of the data iscurrently under way.

148


EXPERIMENTAL REPORT Proposal N° MAT-04-615Instrument V6Adsorption/Desorption of poly(o-

methoxyaniline) layer-by-layer films Local Contact Irina Estrela-LopisRoland Steitz

Principal Proposer: Maria Raposo, Dep. Física, FCT/UNL, Pt Date(s) of ExperimentExperimental Team: Maria Raposo, Dep. Física, FCT/UNL, Pt,

Paulo A. Ribeiro, Dep. Física, FCT/UNL, Pt *February 16th-21th,2002

Date of Report: *12/01/2002Poly(o-methoxyaniline) (POMA) in the emeraldine saltform, i.e., conductive form, is a water solublepolyelectrolyte that can be used to produce conductinglayer–by-layer films. Recently, it has been demonstratedthat hydrogen bonding plays a important role in thePOMA layer-by-layer films formation [1]. In order to gofurther into these interactions, neutron reflectivitymeasurements at the solid/liquid interface wereperformed at different temperatures and for pH=3 andpH=8, this after and before the adsorption of a POMAlayer. Samples for the neutron reflectivity measurements wereprepared by layer-by-layer technique in accordance toref.[2]. A precursor film was prepared onto a siliconblock from 10-2 M aqueous solutions of poly(ethyleneimine) (PEI), poly(allylamine hydrochloride) (PAH) andpoly(styrene sulfonate) (PSS). The precursor layersequence was PEI/(PSS/PAH)5/PSS. The POMAsolution, with a concentration of 0.45 g/L, was obtaineddissolving the polymer in acetonitrile and subsequentlyin D2O (acetonitrile:D2O (1:49)). In order to study thetemperature effect at fixed pH, buffer solutions wereprepared. For the pH=3 buffer solution a 0.1 M citricacid D20 solution and a 0.2 M Na2HPO4 D2O solutionwere used in the proportion 79.45:20.55. The pH=8buffer was prepared dissolving 30.3mg oftris[hydroxymethyl] aminomethane in 25mL of D2O andadding 4 droplets of 1M HCl.The changes in the layer pattern after the adsorption of aPOMA layer onto a layer-by-layer film and submitted toa high temperatures at pH=3. For this purpose the flowcell was filled with the pH=3 buffer solution and thereflectivity curves were measured at the solid/liquidinterface, at different temperatures. The reflectivitypatterns are shown in figure 1, were curve I is thereflectivity curve of the precursor at 25ºC, curve II is thereflectivity curve of precursor+POMA layer adsorbedduring 2h at 25ºC, curve III is the precursor+POMAlayer at 80ºC and curve IV is precursor+POMA layer at25ºC after heating. These results reveal an increase infilm thickness when POMA is adsorbed and asubsequent decrease in thickness when the temperatureis rised to 80ºC. These results are in accordance withprevious results [2]. In addition, thickness changes weremaintained when the temperature was lowered newly to25ºC, indicating irreversible changes on the filmstructure. This conclusion is consistent since it has beenproved that an increase of temperature until 80ºC did notinfluence the precursor film.

0,5 1,0 1,5

1E-4

1E-3

0,01

0,1

1

I II III IV

Ref

lect

ivity

Omega[deg]

Figure 1- Reflectivity curves with pH=3 buffer: I –precursor at 25ºC; II -precursor+POMA layer adsorbedduring 2h at 25ºC; III- precursor+POMA layer at 80ºC;IV- precursor+POMA layer at 25ºC after heating.

0,0 0,5 1,0 1,5

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1E-3

0,01

0,1

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A B C D

Ref

lect

ivity

Omega [deg]Figure 2- Reflectivity curves with pH=8 buffer: A –precursor at 25ºC; B -precursor+POMA layer adsorbedduring 2h at 25ºC; C- precursor+POMA layer at 80ºC;D- precursor+POMA layer at 25ºC after heating.

The reflectivity curves when the flow cell was filled withthe pH=8 buffer solution are shown in figure 2. Curve Ais the reflectivity curve of the precursor at 25ºC, curve Bis the reflectivity curve of precursor+POMA layeradsorbed during 2h at 25ºC, curve C is theprecursor+POMA layer at 80ºC and curve D isprecursor+POMA layer at 25ºC after heating. Theseresults reveal a similar behaviour to previous in pH=3,which is contrary to what is known about POMAadsorbed layers. In fact, POMA is dedoped for pH>6 andnormally tend to desorbed completely from surfaces forhigher pHs which seems does not occur. In conclusion,POMA is stable, i.e., keeps its emeraldine salt formwhen adsorbed onto PSS.

[1] M. Raposo, O.N.Oliveira Jr., Langmuir, 2000, 16(6), 2839[2] R. Steitz et al, Colloids and Interfaces A, 2000, 163, 63

149


EXPERIMENTAL REPORT Proposal N° CHE-04-601Instrument V12Fractal Structures in Poly(N-vinylcapro-lactam)

aqueous solutions decomposed Local Contact W.Treimer,M.Strobl

Principal Proposer: Gy.Torok, Res.Inst.for Solid State Phys. POB-49, H-1525, Budapest, Hungary Date(s) of Experiment

Experimental Team: V.T.Lebedev, Petersburg Nucl. Phys. Inst.,Gatchina, St. Petersburg dist.,RussiaA.Len, Res.Inst.for Solid State Phys. POB-49,H-1525, Budapest, Hungary

15-22.07.01


The high complexing ability of poly(N-vinylcapro-lactam) (PVCL) originates from its chemical structureand the “chair” conformation of chain side rings [1]. Theinteraction between caprolactam rings and water createswater shell. It becomes broken in the range Ts~32-34oCthat leads to the collapse of PVCL coils above TS(spinodal) and to the growth of superstructures [2]. Wehave investigated the PVCL (mass M=1106) in D2O nearthe threshold of coils overlap at C*=0.5 %wt. by spinodaldecomposition. Heating the system from T=32oC~TS upto T=36 oC and then cooling to 23 o C, we tried to verifytransition reversibility. The decomposition was detectedat the lowest temperature (Fig.1). Further the scatteringincreases at small q and then decreases that testifies thegrowth of aggregates’ scale. The intensity distributionsI(q) manifest a large-scale correlation related to fractalaggregates (Fig.1). The local correlation at the scale ofglobule’s diameter (~100 nm) also presents giving aweak interference of scattering from neighbouringmolecules. At q0.01 nm-1 the fractal behaviourdominates in the scattering described by function I(q)=A/qD with two fitting parameters A and D (Table 1). Table 1. Parameters of scattering function I(q)=A/qD.

T, oC A105 arb.un D 32.2 1.01 0.42 3.52 0.07 34.4 1.65 0.33 3.58 0.03 35.2 1.19 0.38 3.58 0.05 36.3 0.82 0.28 3.52 0.06

The exponent D~3.5-3.6 testifies the fractal surface withdimension DS =6–D =2.4-2.5 >2. Surface geometry doesnot alter significantly by temperature increase from theonset to deep separation. The behaviour of scatteringintensity at a given q is characterised by the parameterA(T) proportional to the interface area. It increases byintense phase separation and becomes smaller by theaggregation of small clusters to large structures. Atinitial stage (T=32.2oC) in “high” q-region, q>0.01 nm-1,a weak interference in scattering was observed fromneighbouring molecules aggregated with spacing d~diameter of a globule. At T=32.2oC near the spinodaltemperature TS 32oC we found correlation radius of aglobule rC =30.5 13.1 nm and the characteristic distancebetween molecules d=17225 nm. As a result weobtained globule gyration radius RG = rC6=75 nm anddiameter ~2RG~150 nm close to their spacing d. Thenthe size of aggregates becomes much larger, rC~400 nm,

while the interference is not observable. Therefore bycooling down to ambient temperature, the residualaggregation exists at T~23oC<TS for a long time (30 h).These results confirm the concepts of sponge-likestructure of polymer enriched phase above spinodaltemperature [3]. [1] Yu.E.Kirsh, Poly(N-vinylpyrrolidone) and otherpoly(N-vinylamides): Synthesis and physico-chemicalproperties. (Nauka, Moscow,1998) pp.10-35. [2] V.T.Lebedev, Gy.Torok, L.Cser, et al. Physica B297 (2001) 50-54. [3] S.Koizumi, M.Annaka, S.Borbely, D.Schwann,Physica B 276-278 (2000) 367-368.

Fig.1. SANS from PVCL in D2O by spinodaldecomposition: A). T=32.2 oC; B). T=34.4oC; C).T=35.2 oC;D).T=36.3oC. Lines are fitting functions.

1E-3 0,0110

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C).

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Model: user3

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Instrument V6 Distribution of glucose oxidase in the Nafion entrapment layer of a model glucose biosensor.

Local Contact Roland Steiz

Principal Proposer: Ali Zarbakhsh, Queen Mary, University of London Date(s) of Experiment Experimental Team: J. Bowers, A. Querol-Suquia, A. Zarbakhsh, R. Steitz and R. Krustev Dec 2001

Date of Report: Jan 2002 The immobilisation of non-denatured biomolecules (in this case glucose oxidase) on the transducer surface is an important step in the fabrication of th ebiosensor. One of the more popular methods for immobilisation is to entrap the biomolecules, together with other reagents, in a thin film (membrane) directly attached to the surface of the transducer. Accordingly, the composition of this film, or matrix, has to be chosen carefully so that the stability and function of the entrapped biomolecules are maintained or even enhanced. In addition the film should also permit the transducing mechanism to function satisfactorily. In BIO-04-477, we used the cationic exchanged (perfluorinated) polymer Nafion to entrap glucose oxidase. Nafion is commercilaly available in EtOH/H2O solutions and can be easily spin-coated onto silicon surfaces with control over the film thickness making the films accessible to investigations by neutron reflectometry. We demonstrated that we could produce thin uniform Nafion films which entrapped the glucose oxidase and upon hydration (with and without added D(+)-glucose) the films were shown to expand. The previous measurements (under wet conditions produced spectra with very subtle -yet distinct- structure. On this occasion, we have attempted to utilise contrast match variation of the aqueous subphase to highlight the subtle structural changes and to provide less ambiguous models. In particular, matching the refractive index of the water to that of silicon. The intensities were found to be high enough due to fluorine content of Nafion for subtle structural changes to be resolved. Again we obtained a complete set of data for Nafion films with and without entrapped glucose oxidase. Figures 1, 2 and 3 show the expansion of a Nafion film when in contact with D2O and D2O with glucose. Figure 4 shows the expansion of the same film when in contact with contrast match silicon water. Analysis of these contrast data will eliminate any ambiguity in our models so far. A manuscript on the behaviour of Nafion films with entrapped glucose oxidase is now prepared for submission for publication.

Figure 1

Si / Nafion / AirNafion film ~145Å

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CHE-01-1001-0875 // brandt // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° CHE-01-1001 / CHE-01-875Instrument V1STUDY OF LAMELLAR PHASES FORMED BY

NUCLEOSIDE FUNCTIONALIZED LIPIDS Local Contact Thomas Hauss

Principal Proposer: Piero Baglioni, Dept. of Chemistry, Universityof Florence, Italy Date(s) of Experiment

Experimental Team: Debora Berti, Dept. of Chemistry, Universityof Florence, ItalyEmiliano Fratini, Dept. of Chemistry,University of Florence, Italy

25/03/01-09/04/01 12/11/01-18/11/01back-log


We report a neutron scatteringinvestigation of lamellar phases formed by novel phospholipids bearing nucleosides atthe polar head region. These nucleolipids can interact through stacking and H-bondinteractions, following a pattern thatresembles base-base coupling in naturalnucleic acids (DNA, RNA), i.e they havesimilar recognition properties. Bilayerstacks formed of DPP-Adenosine, DPP-Uridine and their 1:1 mixture were investigated after equilibration in a 98 %relative humidity atmosphere. DPP-Adenosine spectrum can be accounted (inanalogy to DPPC) by a lamellar phase witha smectic period of about 60 Å. DPP-Uridine displays a not so straightforwardbehavior, that we have tentatively ascribedto the coexistence of lamellae with differentsmectic periods. In the 1:1 mixture thelamellar mesophase of DPP-Uridine isretained, suggesting a specific interactionof the uridine polar head group with theadenosine moiety of the DPP-Adenosine. It should be stressed that this behavior canbe considered as an indication of the recognition process occurring at the polarhead group region of the mixedphospholiponucleoside membrane.

D. Berti, E. Fratini, S. Dante, T. Hauss andP. Baglioni: Applied Physics A (2002) inpress.

Spacing (A)DPP-Adenosine 54.5DPP-Uridine (1) 63.3DPP-Uridine (2) 56.8DPP-Uridine (3) 51.91:1 Mixture 61.5

152


EXPERIMENTAL REPORT Proposal N° BIO-01-998Instrument V1Peptide Membrane InteractionLocal Contact Dr. Th. Hauss

Principal Proposer: Dr. Regine Willumeit, GKSS, Geesthacht Date(s) of ExperimentExperimental Team: Dr. Jörg Andrä, Kay Oetzmann, F. Förster, S. Hubo,

M. Kruse,Universität Hamburg, Hamburg 01.-15.05.2001


Increasing resistance of pathogenic bacteriaagainst antibiotics is a severe problem in healthcare. Natural antimicrobial peptides and derivativesthereof have emerged as promising candidates for"new antibiotics". These peptides act by directphysical destabilization of the target cell membrane.Nevertheless, they exhibit a high specificity forbacteria over mammalian cells. However, theirmechanism of action is not well understood.We were interested in cytotoxic and antibacterialproteins from porcine immune cells (NK-lysin) andpathogenic amoeba (amoebapores), ratherhomolog proteins of appr. 8 kDa, consisting nearlyexclusively of amphipathic alpha-helices. Bystructure/function analysis with synthetic peptides,we identified a core region of these proteins to bebiologically active. The antimicrobial activity ofthese peptides was enhanced by the definedexchange of single amino acid residues. On theother hand, their cytotoxic activity was significantlylowered. Thus, these new peptides fulfill therequirements for therapeutic antibiotics. Still, themanner of interaction with the membrane and themechanisms of membrane lysis are not wellunderstood. This project investigates the influence of the NK-lysin derived synthetic peptide NK2 on a modelmembrane system consisting of differentphospholipids.As a first model for an prokaryotic, Gram-negativemembrane the lipids POPE and POPG were mixedin a ratio of 80:20. Membranes in 10 mM Na-phosphate buffer were prepared and kept under98% humidity (water) during the measurements atthree different contrast conditions (100% (Figure 1),50%, 0% D2O).

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Several peaks were found but it can clearly be seenthat a lamellar phase with a repeat distance of 65 Åwas established. Our previous X-Ray experimentson liposome showed a similar behaviour. Therepeat distance from POPE alone would be 53.2 Å,the value for POPG is not known from literature.In the next step two membranes were doped withthe protonated NK2 (Figure 2) and a partiallydeuterated NK2 (L23D) (Figure 3).

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Figure 3: Spectra of the POPE:POPG membranedoped with NK2 labelled by a deuterated leucine atposition 23 (100% D2O).

In both cases an additional phase shows up andthe repeat distance of POPE:POPG decreases to63 Å.Future measurements with the synthetic peptideNK2 deuterated on a N-terminal leucine residueand deuterated in both positions (N- and C-terminal) will unequivocally show if the peptideinserts into the membrane.

153


EXPERIMENTAL REPORT Proposal N° BIO-01-1076Instrument V1Peptide Membrane InteractionLocal Contact Dr. Th. Hauss

Principal Proposer: Dr. Regine Willumeit, GKSS, Geesthacht Date(s) of ExperimentExperimental Team: Dr. Jörg Andrä, Kay Ötzmann,

Universität Hamburg, Hamburg 02.-16.12.2001


It is well known that antibacterial peptides withsometimes less than 30 amino acid residues candisturb the structure of a membrane completely.This interaction which causes the destruction of themembrane is a process which is not wellunderstood. The project described here,investigates the influence of the synthetic peptideantibiotic NK2 on a multilamellar system consistingof different phospholipids. The peptide NK2 was derived from NK-lysin, anantibacterial and cytotoxic protein, which wasisolated from porcine NK-cells. It belongs to thefamily of saposin-like proteins, consisting of anamphipathic alpha-helical bundle stabilized bydisulfide bonds. Starting with a homologue proteinfamily from pathogenic amoeba (amoebapores), weidentified the alpha-helical core region ofamoebapores to interact with phospholipdmembranes. A synthetic peptide (NK2),representing the corresponding region of NK-lysin(res. 39-65, with minor modifications), was verypotent against various bacterial strains andCandida albicans, but does not exhibit cytotoxicityagainst human cells. Thus, these peptide is anpromising candidate for the treatment of bacterialand fungal infections. However, the manner ofinteraction with the membrane and the mechanismsof membrane lysis is not understood. The proposedexperiments should show where the peptideinteracts with phospholipid model membranes.As a first model for a prokaryotic, Gram-negativemembrane the lipids POPE and POPG werechosen and measured in 10 mM Na-phosphatebuffer kept under 98% humidity (water) during themeasurements at three different contrast conditions(100%, 50%, 0% D2O) at 20° C.

Figure 1: Pure model membrane of POPE in buffer.

Surprisingly at higher orders the peak splits intotwo. This is even more pronouced for POPG while itdisappears if the membranes are prepared in waterinstead of buffer (Figure 2).

Figure 2: Scattering of POPG membranes.

The measurements of a model membrane ofPOPE:POPG (80:20) prepared in water with thesynthetic peptide [H]NK2[I2D] where the secondamino acid isoleucine was deuterated gave nearlythe same scattering pattern as previousmeasurements (Figure 3). But again the stronginfluence of the buffer can be seen.

Figure 3: Comparison of the spectra of thePOPE:POPG membrane doped with NK2 labelledby a deuterated isoleucine at position 2 prepared inwater with a membrane doped with NK2 labelled atposition 23 prepared in buffer (100% D2Oatmosphere) .

Further investigations will be focused on theinfluence of the buffer system on the structure ofthe membrane.

154


EXPERIMENTAL REPORT Proposal N° Bio-01-1002Instrument V1Phospholipid Phase Transitions Observed

with an “Excess Water” Cell Local Contact Thomas Hauß

Principal Proposer: Jeremy P. Bradshaw, University of Edinburgh Date(s) of ExperimentExperimental Team: Thad Harroun, University of Edinburgh

Sarah Davies, University of EdinburghThomas Hauß, HMI, Univ. Düsseldorf

13 – 28 May 2001


Biomembrane fusion is a ubiquitous processthat plays a crucial role in such fundamentalevents as spermatozoid-egg fusion andmitosis. Despite this fact, the molecularrearrangements of the lipids and the precisekinetic events involved are still uncertain.This is largely because the fusion event istransient and involves only local, isolatedpatches of lipid. Short peptides termed fusionpeptides, from enveloped viruses, are able topromote the fusion of phospholipid bilayers.

The precise molecular events that occur duringpeptide-induced membrane fusion are stillunclear. The membrane leaflets, composed ofphospholipid molecules, must rearrange intohighly curved intermediates prior to fusionpore development. It has been demonstratedthat peptides that lower the bilayer (Lα) toinverted hexagonal (HII) phase transitiontemperature in model membranes, can alsopromote membrane fusion through this kind ofbilayer destabilisation. A large fraction of thelipids of many biological membranes form theHII phase when purified and hydrated underphysiological conditions. These lipids have been termednonbilayer lipids in contrast to the bilayer lipids thatform lamellar structures under the same conditions. It isthought that, although membranes are bilayers most ofthe time, the high concentration of nonbilayer lipids hasfunctional significance in allowing the membranes toform transient nonbilayer structures because vitalprocesses, including fusion, would be topologicallyimpossible with intact bilayers.

Highly-curved lipid mesomorphs, similar to thoseinvolved in fusion, also occur during the lamellar liquid-crystal/inverted cubic (Lα/QII) phase transition and thelamellar liquid-crystal/inverse hexagonal (Lα/HII) phasetransition. The ability of a number of agents to promotefusion appears to be correlated to their ability to lowerthe Lα/HII transition temperature. Although the QII andthe HII phases, which are kinetically stable, are unlikelyto exist at the site of a developing fusion pore,knowledge about the topology of the interface as thesephases begin to form has clear implications for ourunderstanding of biological fusion mechanisms.

We have been studying the relationship between the Lαto QII phase transition and the fusion mechanism. Oursamples typically take one of two forms. Alignedsamples consist of stacks of phospholipid bilayers on a

solid substrate. They are formed by depositingchloroform solutions of lipid on the quartz or siliconsubstrate, removing the solvent under vacuum andhydrating the lipid from a humid atmosphere. The highdegree of alignment ( 0.5° mosaic spread) allows high-resolution studies ( 0.5Å with suitable deuteriumlabels). However, these samples have not been optimalfor phase-transition studies, where the relatively narrowwater layer between adjacent bilayers can interfere withthe structural rearrangements of the lipid molecules. Forthese studies, the samples usually take the form of adispersion of lipid in excess aqueous buffer. The lipidmolecules are not aligned in these samples so, incomparison, the resolution limit of the data is very poor.

A new type of sample cell combines the best features ofthese two approaches. An aligned stack of bilayers isheld in fully hydrated (excess water) state. In theexperiment reported here, we have performed trialmeasurements with such a cell, developed by Dr ThomasHauß at the HMI. The results show that the phasetransition behaviour of a phospholipid in one of thesecells is comparable to that previously observed from alipid dispersion, but sample alignment is preservedthroughout the transition. This opens up opportunitiesfor obtaining high-resolution data from non-bilayerphases.

Figure. The benefits of sample alignment in diffractionmeasurements from non-lamellar phase lipid. Left: modelleddiffraction data using aligned sample. Right: the same datasmeared to simulate a non-aligned sample (lipid dispersion).Note: i) Circular smearing of Bragg peaks decreases intensitydramatically and limits resolution. Two of the off axis peaks areno longer visible at all. ii) Some of the peaks overlap in the righthand panel; they could not be separated mathematically. iii)Indexing of the peaks in the smeared sample would be very muchmore difficult.

155


EXPERIMENTAL REPORT Proposal N° BIO-01-1078Instrument V1Lipid Interactions of ADP-Ribosylation

Factor-1’s Amphipathic Helix Local Contact Thomas Hau

Principal Proposer: Sarah Davies, University of Edinburgh Date(s) of ExperimentExperimental Team: Thad Harroun, University of Edinburgh

Jeremy Bradshaw, University of EdinburghThomas Hau, HMI

30/07/01 - 19/08/01


IntroductionADP-Ribosylation Factor 1 (ARF-1) is a

small intracellular G protein, currently of greatinterest as it plays a key role in cell traffickingand cell signalling mechanisms. ARF-1 acts as acellular biotimer, both initiating and terminatingspecific cell functions. Since ARF-1 is onlyactive in cells when membrane-bound, andsince the lipid content of the membrane affectsARF-1’s membrane residence time, it isimportant to understand how this proteininteracts with membranes composed ofcommon cellular lipids.

The membrane binding domain of ARF-1,which contains an amphipathic helix of uncertainlength, is thought to lie along the surface ofmembranes, reversibly anchoring ARF-1 to cellmembranes.

Our goals are:1) to determine the length of ARF-1’s membranebinding helix when inserted in a lipid bilayer, and2) to locate the helix within lipid bilayers.

Experimental ProceduresFour 15 mer peptides representing the

unmyristoylated amino terminus of ARF-1 weresynthesised. We used unmyristoylated peptides,as they are water soluble and thus suitable foruse in complementary circular dichroism (CD)experiments. The synthetic peptides comprisedthe undeuterated peptide, and three peptideseach containing a specific deuteration at Phe 5,Phe 9 or Phe 13.

Samples were prepared as describedpreviously1, using lipid mixtures of 70%dioleolyphosphatidylcholine (DOPC) and 30%dioleoylphosphatidylglycerol (DOPG), with apeptide content of 3 mol%.

Experimental conditions and datacollection on V1 followed our previouslyestablished routines1, with a sampletemperature of 25C. Samples were studied atthree different D2O concentrations and, for the8% D2O samples, at two different humidities, tofacilitate data phasing and scaling.

ResultsConsecutive scans of each sample

showed that excellent sample equilibration hadbeen achieved. A minimum of five orders ofdiffraction were obtained for each of the ARF-1peptide samples and for the pure lipid system.As an example, the diffractogram for theundeuterated ARF-1 peptide sample is shownbelow.

Since four diffraction orders are sufficient toaccurately determine the position of a labelwithin a lipid bilayer2, we should be able toprecisely locate our deuterated residues.

The results of these neutron experimentswill be combined with CD measurements ofpeptide secondary structure, performed incollaboration with Dr. S. Kelly, (University ofGlasgow), and model fitting will be used tolocate the ARF-1 peptide in our anionic lipidbilayers.

AcknowledgementsGrateful thanks to Dr. Thomas Gutberlet forexpert technical help with V1 at the start ofthese experiments. Financial support by TheWellcome Trust is gratefully acknowledged.

References1. Bradshaw, J.P., et al., BENSC Exptl. Rep.2000, 155.2. Gordeliy, V.I., and Chernov, N.I., Acta Cryst,1997, D53,377.

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156

EXPERIMENTAL REPORT

Structural analysis of H2O and detergent within PS Icrystals

Proposal N BIO-01-1075

Instrument V1

Local Contact

T. Hau


1. 10. - 15. 10. 2001Principal Proposer: Petra Fromme, Technische Universitat BerlinExperimental Team: Joachim Frank, TU Berlin, Thomas Gutberlet,

HMI Berlin, Thomas Hau, Heinrich-Heine-Universitat Dusseldorf, Silvia Dante, TU Darmstadt


Neutron scattering experiments with largephotosystem I (PSI) crystals (1 mm3 volume)soaked in 100% D2O buer were performedat the V1 diractometer at BENSC, Hahn-Meitner-Institut. Data sets of up to 180 per-pendicular to the c-axis could be measured withthe setup of this diractometer. These mea-surements yielded low resolution diraction datadown to 40 A collected perpendicular to the c-axis of the unit cell, Figure 1 shows two examplesof diraction patterns collected.

By the experiments at the HMI the han-dling of the PSI crystals for the long termneutron diraction experiments with exposuretime up to several days were improved consid-erably. Optimal results were achieved with sil-iconizied quartz capillaries preventing crystalsto dissolve during the experiments. Using ad-ditional diraction data collected at the DB 21diractometr at ILL in Grenoble, which showedmore and brighter re ections compared with themeasurements at HMI due to the higher overallintensity of the neutron scource in Grenoble, thecollected data sets were enlarged but the overallresolution was the same as at HMI. Although,the combined ILL data sets do not allow datacollection of more than 45 perpendicular to thec-axis.

As our aim is to solve the structure of de-tergent within the crystals we have to recordadditional complete data sets with 0, 20 and70% D2O containing buer for phase determina-tion in subsequent experiments at the availablediractometers.

Figure 1: Diraction pattern of PS I crystalsoaked in D2O rotated perpendicular to the c-axis measured at the Membrane-diractometerat HMI, = 4.53 A. Re ections visible are at 2= 2.06, ! = -63.5 d = 135.5 A, 2 = 2.69, != -56.5 d = 97.0 A and 2 = 3.14, ! = -53.5

d = 81.8 A (top pattern) and at 2 = 2.21, != -12.5 d = 117.4 A, 2 = 3.05, ! = -7.5 d= 85.1 A and 2 = 6.00, ! = -6.0 d = 43.2 A(bottom pattern). The strongest re ections maybelong to a lamellar structure.

157

EXPERIMENTAL REPORT

Interaction of β-amyloid peptides with lipid membranes

Proposal N EF

Instrument V1

Local Contact


6. 3. - 25. 3. 200127. 8. - 9. 9. 200129. 10. - 11. 11. 2001

Principal Proposer: S. Dante, HMI and TU Darmstadt

Experimental Team: T. Hauß , HMI and Heinrich-Heine-Uni DusseldorfNorbert A. Dencher, TU Darmstadt


Introduction

One hallmark of Alzheimer’s disease (AD) aresenile plaques found in brains of patients withAD; the main component of the plaques are β-amyloid peptides of different length. In partic-ular a short framgent, i.e. Aβ(25-35) has beenproven to be toxic to neuronal cells and it hasbeen proposed to activate the process of neu-ronal disfunction. In previous experiments weinvestigated by neutron diffraction the interac-tion of Aβ(25-35) with model membranes and wewere able to locate the C-terminus of the pep-tide inside the lipid bilayers. Different behaviourwas detected in neutral and anionic membranes(manuscript submitted for pubblication). In oneof the new experiments we have extended ourprevious investigation to membranes resemblingthe natural nerve membrane and therefore con-taining a 40% (molar) of cholesterol. In addi-tion, in order to simulate as close as possiblephysiological conditions, we studied in a secondexperiment lipid multilayers obtained from smallunilamellar vesicles.


As previously described (February and August2000), two Aβ(25-35) peptides were synthesized,one with protonated and one with deuteratedleucine (10 deuterons) in position 24. A cholo-form solution of palmitoyloleyl phosphatidy-cholinec(POPC), palmitoyloleyl phosphatidyser-ine (POPS) and cholesterol was sprayed ofquartz slides and then equilibrated at 98% rel-ative humidity. The total lipid amount was20 mg. Two samples containing 3% (molar) ofthe peptide, either protonated or deuterated,were prepared as well. In the presence of choles-terol the samples showed a mosacity of about

0.2. The diffraction measurements were per-formed at different isotopic ratios of the atmo-sphere, namely 1:0, 0,5:0,5, 0,2:0,8, 0,08:0,92, 0:1D2O/H2O. Neutron diffraction spectra showedup to the 6th diffraction order. The data eval-uation to obtain the scattering density pro-file of the membrane and the localization ofthe label in the lipid bilayers are currently inprogress. To achieve physiological conditions,test experiments with unilamellar vesicles of dif-ferent lipid composition were also carried on. Inparticular samples of POPC, POPC/POPS, andPOPC/POPS/cholesterol were prepared. Thevesicles were obtained by sonication; the aqueoussolution containing the vesicles was slowly driedon quartz slides and then rehydrated at 98% rel-ative humidity. This procedure resulted in lipidmultilayers of broad mosaicity; up to five diffrac-tion orders were measured. Further experimentsto incorporate the Aβ(25-35) in the vesicles areplanned.

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158


EXPERIMENTAL REPORT Proposal N° BIO-03-139Instrument V3Interhelix Fluctuations in BacteriorhodopsinLocal Contact Dr. Lechner

Principal Proposer: W. Doster, TU München Date(s) of ExperimentExperimental Team: R. Lechner, HMI

W. Doster, TU MünchenTh. Hauß, HMI

20.11.00


Breathing motions of secondary structure ele-ments of proteins play an important role inlarge scale conformational changes,open/closed transitions, regulation and folding.The goal of this project is to characterise theinterhelix fluctuations of oriented bacteriorho-dopsin monomers using elastic and inelasticneutron scattering. In this experiment the effectof the hexagonal lattice on concerted motionswas investigated. In a parallel V1 experiment(see report BIO-01-934) it was shown that thehexagonal lattice of BR trimers melts reversiblyat 85 °C, while the intramolecular structure ispreserved. The effect of lattice constraints onmolecular motions was investigated on V3.Inelastic scattering spectra were taken at 70,80, 85 and 90°C, below and above the phasetransition. The elastic resolution was modifiedusing a neutron wavelength of 5 and 8 Å. Be-tween 70 and 80°C the observed spectralchanges were small. Above 80°C, the elasticintensity decreases and the spectral wingsbroaden significantly as shown in fig.1:

fig.1: Neutron scattering spectra at a fixed scatteringangle, below and above the phase transition.

Decreasing the temperature to below the tran-sition reproduced the inital results. A preliminary analysis suggests that both am-plitude and relaxation rate of structural fluctua-tions increase notably as a result of releasedlattice constraints. This result is interestingsince the hexagonal lattice is balanced by we-aker forces than the trimer and the intramole-cular structure which are not affected by phasetransition.

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159


EXPERIMENTAL REPORT Proposal N° BIO-03-156

Instrument V3Vibrational Change on Ligand Binding toProteins Local Contact

Dr. Ruep Lechner

Principal Proposer: Jeremy C. Smith, Uni. Heidelberg Date(s) of ExperimentExperimental Team: Jörg Pieper, Arnaud Desmedt, BENSC

Martin Oettl, Uni. Waikato, New ZealandErika Balog, Uni. Heidelberg

29.10 – 12.11. 2001


An understanding of the phenomenainfluencing molecular association is offundamental importance both in biology and tobiotechnological/pharmaceutical companies.Some of the important factors, such ashydrophobic, hydrogen-bonding, electrostaticand van der Waals interactions, are wellappreciated and their effects can be estimatedin an accurate way. However, a further,important but poorly understood, contributionto binding thermodynamics arises fromvibrational effects. We aim to understand the change in vibrationaldynamics and thermodynamics onbiomolecular association by combininginelastic neutron scattering with normal modeanalysis and MD simulations. In our currentwork the binding of methotrexate (MTX) todihydrofolate reductase (DHFR) isinvestigated. This system is fascinating becauseof its biological importance: DHFR catalyzesthe nicotinamide adenin dinucleotide(NADPH) dependent reduction ofdihydrofolate to tetrahydrofolate, which isessential for the synthesis of thymidylate, abuilding block of DNA - in this way theinhibition of DHFR’s activity stops DNAsynthesis and results in cell death, which has acrucial importance in rapidly proliferating cellssuch as cancer cells.

To accurately determine the harmonicvibrational spectrum the sample was cooled to120K. In order to determine the anharmoniccontributions to the scattering the inelasticspectrum of the sample was measured at 280Ktoo.

The samples were as follows:

for low resolution (E=180eV)1. DHFR/NADPH in D2O at 280K for 24 hours2. DHFR/NADPH +MTX in D2O at 280K for

20 hours

for high resolution (E=100eV)3. DHFR/NADPH in D2O at 120K for 45 hours4. DHFR/NADPH +MTX in D2O at 120K for

45 hours5. DHFR/NADPH in D2O at 280K for 44 hours6. DHFR/NADPH +MTX in D2O at 280K for

44 hoursAs the figure shows a difference can be seen inlow frequency range of the spectra from thefree and complex form of the enzyme at thelow resolution.

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S(q,

)

Fig. Dynamic structure factor at 280K, 180eV resolution and at 740 forDHFR/NADPH without (red curve) and with MTX (blue curve).

The resolution was increased in order to detectthe low frequency modes better. We are inprocess of determining weather the detectednodes are statistically significant. The densityof states will be determined by fit of S(q,)spectra and the related thermodynamicquantities will be calculated.

160

PHY-03-0180 // hgrimm // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° PHY-03-0180Instrument V3Dynamics of DNA at different levels of humidityLocal Contact Ruep Lechner

Principal Proposer: Grimm Hans, FZ-Juelich Date(s) of ExperimentExperimental Team: Lechner Ruep, HMI-Berlin

Desmedt Arnaud, HMI-BerlinCo-proposer Sokolov Alexei, Uni-Akron Akron,Ohio,USA

2.7.’01-12.7.’01

Date of Report: 16.12.’01

Relaxational motion (< 1meV) of DNA is trig-gered by adsorbed water (optimum regularityof the basepairs (bp) is achieved by about 15water molecules/ bp). The resulting quasielas-tic scattering exhibits a stretched exponentialshape (Cole-Davidson function).

Fig.1 shows the spectra obtained for the ex-tremely tightened resolution (i =12 Å) togetherwith the expectation due to previous back-scattering- and IN5 data at i =8 Å.

0.01 0.1 1 10

6008001k

2k

4k

6k8k

10k

20k

40kFig.1

expected for15 D

2O/bp 320K 290K 210K

11.7 D2O/bp

320K 210K

0.8 D2O/bp 320K 210K

resolution limit

''(

) [a.

u.]

energy transfer / meV

Two conclusions may be drawn; (i) this spec-trometer configuration is too tight for quantita-tive tests at low humidity and/or approachingthe ‘glass-temperature’ of 210K, and (ii) theobserved quasielastic intensity at 320K &11.7w/bp is about equivalent to the expecta-tion for 290K & 15w/bp. In fact, subsequentexamination of this sample revealed a loss of0.137 g water (~20%) w.r.t. to the IN5 experi-ment, which explains the slower relaxation. Itfollows, that one would have to go to 320K &

20w/bp in order to observe the expected ‘flat-tening’ of the quasielastic response within thistightened resolution range.

Consequently, the instrument setup wasswitched to i =8 Å (factors 2.7, 5, 0.15 in resolu-tion, intensity, background) and a NaDNA-samplecomplexed with ‘bipy’ (bipyridyl-ethylenediamine-Pt 2+ /2bp) was investigated (Fig.2).

0.1 1 10 100

2k

4k

6k8k

10k

20k

40k

60k80k

100k

D2O--libration

-0.25

Fig.2

14.9 D2O/bp

NaDNA with bipy 320K 290K 250K 210K

LiDNA 320K

resolution limit

''(

) [a.

u.]

energy transfer / meV

The measurements (Fig.2) show that the re-laxational behaviour (apparent slope ~ -0.25)with and without the ‘bipy’-complex is quitesimilar. The most prominent difference is theenhanced susceptibility for the complexedDNA in the transition region between relaxa-tional and external vibrational response (0.2 –5 meV). Discrepancies between observationand additive models were apparent in this re-gion for the previous measurements of LiDNAand now even more so for the complexedNaDNA

161


EXPERIMENTAL REPORT Proposal N° EFInstrument V3Density of Phonon States in the Light-

Harvesting Complex II of Green Plants Local Contact

Principal Proposer: J. Pieper, HMI Date(s) of ExperimentExperimental Team: R. E. Lechner, A. Desmedt, HMI

K.-D. Irrgang, G. Renger, Max-Volmer-Institut,TU Berlin

12.11. – 18.11.2001


The primary steps of photosynthesis comprisethe generation of electronically excited statesby light absorption in pigment-proteincomplexes referred to as “antennae” as well asultrafast excitation energy transfer (EET) toreaction center complexes. The majorconstituent of the antenna of green plants isthe light-harvesting complex of photosystem II(LHC II) which is embedded into the thylakoidmembrane. The LHC II protein forms a trimerof subunits each containing 12 - 13 chlorophyll,at least two carotenoid molecules, oneamphipathic and three membrane spanning -helices. Time-resolved spectroscopic studies revealthat EET in LHC II is ultrafast with kineticcomponents in the femto- and picosecondrange. A detailed understanding of this rapiddynamics requires information on pigment-pigment and pigment-protein interactions aswell as a thorough investigation of the couplingof the purely electronic transitions of a pigmentto low-frequency vibrational modes of theprotein matrix (phonons). So far, electron-phonon coupling in antennacomplexes has been primarily studied byoptical spectroscopies at low temperatures. Inthe case of LHC II, a one-phonon profile with amean phonon frequency m of 18 cm-1, a widthof ~ 20 cm-1 and a coupling strength S = 0.8 at4.2 K a hole-burning (HB). In contrast to this,fluorescence line-narrowing (FLN) spectro-scopy yielded m = 15 cm-1 and a stronglyasymmetric one-phonon profile with a width ofabout 100 cm-1 at 4.2 K [1].In the present experiment the density ofphonon states of LHC II was studied attemperatures of 5 and 100 K by inelasticneutron scattering (INS) experiments withincident neutron wavelengths of 2.0 and 3.5 Åcorresponding to elastic energy resolutions of921 and 235 µeV, respectively (see [2] fordetails). LHC II complexes were solubilized ina D2O-containing buffer solution, so that thecontribution of the solvent had to bedetermined by separate experiments.

Figure 1 shows INS spectra of solubilizedLHC II (full line) and buffer solution (dashedline) obtained with an incident neutronwavelength of 3.5 Å at a temperature of 100 K.The former and latter exhibit apperentlydifferent shapes with maxima at about 3 and6 meV, respectively.

100 K

NEAT

Eelast = 0.9 meV = 3.5 A

0 5 10 15 20

0

0.5

1.0

1.5

ENERGY TRANSFER [meV]

S (Q

,) [

arbi

trar

y un

its]

°

Figure 1

Thus, the density of phonon states of LHC IIcan be extracted by fitting the Q-dependenceof the INS spectra at different temperatures [3].The results will also be compared to thosegathered from optical spectroscopy.

References:1. Pieper, J.; Schödel, R.; Voigt, J.; Irrgang,

K.-D.; Renger, G., J. Phys. Chem. B (2001),105, 7115-7124 and references therein

2. Pieper, J.; Irrgang, K.-D.; Renger, G.;Lechner, R.E., Applied Physics A (2001), inpress

3. Pieper, J.; Irrgang, K.-D.; Renger, G.;Lechner, R.E., to be published

162

BIO-04-0585-0635 // brandt // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° Bio-04-585 Bio-04-0635Instrument V4Report about characterisation of PEI/DNA-

complexes by SANS Local Contact Dr. Hoell

Principal Proposer: Lukowski, Institute of Marine Biotechnology,Greifswald, Germany 1.2-4.2.2001

Experimental Team: Fischer, Institute for Pharmacy, UniversityMarburgLukowski, Inst. of Marine Biotech., GermanyArmin Hoell, Hahn-Meitner-Institute, Berlin

5.9.-9.9.2001


Introduction

The prospect of treating genetic, neoplastic andinfectious diseases through gene andoligonucleotide therapy has engenderedconsiderable effort towards the development ofgenes and gene transfer vectors. Polyethylenimine(PEI), a synthetic, branched polymer with a highcationic charge density has been demonstrated to bea highly useful reagent for the non-viral delivery ofDNA and RNA both in vitro and in vivo. Thepolymer attracts special interest due to itslysosomal buffering capacity (proton spongehypothesis), potentially protecting DNA fromdegradation by lysosomal nucleases. Althoughmany results are published about the biologicalcharacteristics of PEI, the structure of the polymer/DNA complexes and the proton sponge hypothesisare not fully understood. No conclusive evidence ofthe relationship between PEI structure and thebiological properties of the polymer and its DNA-complexes has been reported.

Results and Discussion1. Characterization of the structure of PEI independency of polymer concentration

High (HMW, 800 kDa) and low (LMW, 3 kDa)molecular weight polyethylenimine were characterizedby different molecular sizes and distributions. Accordingto our GPC measurements (Pharm Res. 1999, 16, 1273),HMW-PEI showed a broad distribution of the molecularweight, whereas the LMW-PEI demonstrated a lowerpolydispersity and a homogeneous distribution. Forhighly concentrated PEI suspensions in water (50%) aself-arrangement could be observed, no monodispersesytems were detected. Formation of nanoparticles wasobserved at polymer concentrations between 5-20% withparticles sizes which were significantly different fromthe particle sizes of the highly concentrated PEIsolutions.

2. Characterization of the PEI/DNA complexes

Complexes of DNA with LMW-PEI formed small andmonodispersely distributed particles in bidistilled water.

This agrees with photon correlation spectroscopymeasurements, where also homogeneously distributedsmall sized complexes were detected. A surplus of PEInitrogen over the DNA phosphate seems to be necessaryfor the condensation of the large plasmid DNA to smallparticles. A calculation of the different models will bedone.

0,1 10,1

1

DNA-Pei (40 µl)

Q [1/nm]

corr

ecte

d in

tens

ity

0,1 10,1

Pei-DNA (pH-value 10)

Q [1/nm]

corr

ecte

d in

tens

ity

Fig. 1 SANS-curve of pure PEI-nanoparticles and ofPEI/DNA-complexes at a pH-value 10

3. Characterization of PEI/DNA complexes independency of pH

A strong dependency of the size of LMW-PEI/DNAcomplexes on different pH values was observed.Whereas at pH 10 the complexes were compact withoutany detectable shells, at pH 3 the size of and the distancebetween the PEI/DNA particles increased presumablydue to an expansion of the complexes. Presumably, theresulting scattering curve is a superposition of theinterparticulary interaction function with the function ofthe relatively monodisperse DNA/PEI complexes. Wesuggest that the complexes form a core-shell-structure atpH 3 or due to swelling at low pH a sponge with acompact, non-swollen core. These results correspond tothe proton sponge hypothesis of J. P. Behr (Chimia,1990, 51, 34). For accurate description of the complexstructures further modellings are underway at themoment. For a detailed description of these systems, weinvestigate the influence of different parameters such asthe nitrogen/phosphate ratio, pH and ionic strength onthe complex composition at present.

163

EXPERIMENTAL REPORT Proposal N° MAT-04-592Instrument V4Characterization of Protein Conformation

along the Catalytic Pathway Local ContactDr Wiedenmann,A. Hoell

Principal Proposer: S. Magazù, Dip. Fisica Univ. Messina Date(s) of ExperimentExperimental Team: S. Magazù, Dip. Fisica Univ. Messina

F. Migliardo, Dip. Fisica Univ. MessinaA. Wiedenmann, A. Hoell, HMI

1-6/3/2001


Nucleotide metabolism and replication ofnucleic acids are processes of fundamentalimportance. The fidelity of DNA replicationis of ultimate importance in all livingorganisms and is accounted for by severalregulatory mechanisms (e. g. proof-reading,excision repair, mismatch repair) whichrepair the mistake but do not prevent itsoccurrence. The enzyme deoxyuridine 5'-triphosphate nucleotidohydrolase (dUTPase)catalyses the hydrolysis of dUTP to dUMPand pyrophosphate. It is involved in theremoval of dUTP from the dNTP pool thuspreventing this nucleotide to be available forDNA polymerase and therefore all theconsequences resulting directly from theincorporation of uracil in DNA. Futhermore,it plays an essential role in de novobiosynthesis of dTTP by furnishing thesubstrate for thymidylate synthase. Itswidespread presence in a variety oforganisms, including bacteriophages andcertain retroviruses with a relatively smallgenoma, suggests that the dUTPases are vitalto DNA replication in all systems. The activesite closure is initiated by the attachment ofthe gamma-phosphate of the substrate to theC-terminal arm of the protein. There are twodistinct conformations for the active site,termed open and closed. In the crystallinephase dUTPase has typical dimensions ofaround 60 and 45 Å. The SANS experimentwas performed on dUTPase/D2 mixtures fortemperature values of T=8°C and T=37°C.Corrections for inelastic effects, multiplescattering, absorption, sample container andbackground were taken into account. Weobserve that the behaviour of the intensity asa function of Q reveals any important changein the investigated temperature range, thenwe conclude that in this temperature range

the protein is not yet denaturated. In thefitting procedure an ellipsoidal model for thesimulated structure of the protein has beenused. The fitting model allows to calculatethe form factor for a monodisperse ellipsoid(ellipsoid of revolution) with uniformscattering length density. The form factor isnormalized by the particle volume such thatP(Q) = scale*<f*f>/Vol + bkg, where f is thescattering amplitude and the < > denote anaverage over all possible orientations of theellipsoid. By means of this model, we obtain,at all the investigated temperatures, for thesemiaxes the values of about 28Å and 18Å,indicating that, in the investigatedtemperature range, the structure of theprotein is maintained in solution. The smallersize in solution is due to the deuterationprocess, that makes the protein core visibleto the probe.

164


EXPERIMENTAL REPORT Proposal N° CHE-04-593Instrument V4A structural study of living polymers formed by

self assembling of PLNs Local Contact Dr. Uwe Keiderling

Principal Proposer: Piero Baglioni, Dept. of Chemistry, Universityof Florence, Italy

Date(s) of Experiment:

Experimental Team: Debora Berti, University of Florence, ItalyU. Keiderling, TU Darmstadt, HMI Berlin 19-25 Feb 2001


Aim of this proposal was the structuralcharacterization of the micellar growth, takingplace thanks to a volume fraction increase ofdilauroylphosphatydilnucleosides in aqueoussolution. These amphiphilic molecules, whichhave been synthesized in our laboratory inFlorence, merge the self-assemblingproperties of phospholipids with the molecularrecognition characteristic of nucleic bases.They have enormous interest both from afundamental point of view and from anapplicative standpoint as self-assembledprodrugs. Self assembling topology is drivenby the curvature preferences of the surfactantmolecules. Dilauroylphosphatydilnucleosidescan a priori be considered as excellentcandidates to give rise to an extended micellargrowth, thanks to the length and the hindranceof the hydrophobic chains; but this conditionhas to be fine-tuned with a proper choice of theionic strength of the aqueous medium in orderto modulate electrostatic repulsion betweencharged phosphate groups on the polar head.SANS is a unique experimental technique tohighlight the structural features of micellarsolutions with an extended axial growth,especially if data are merged with static lightscattering that gives access to the globaldimension of the aggregates.Neutrons probe structure on a more localscale, providing information about micellarflexibility and cross-section. The –1 scalingexponent displayed in a log-log plot of thescattering pattern is a decisive evidence of alocally cylindrical structure. Base-baseinteractions at the micellar surface can altermicellar flexibility and micellar structure; wehave previously investigated the behavior ofDLP-Uridine. In this proposal our aim was to characterizemicellar solution of DLP-Adenosine and a 1:1mixture of DLP-Adenosine and DLP-Uridine, inorder to highlight how self-stacking andmolecular recognition affect structuralparameters on a mesoscopic scale. Threedifferent configurations (i.e. sample-detector

distances) have been employed in order tobenefit from the full q range available atBENSC.Figure 1 reports the scattering pattern of DLP-Adenosine micellar solutions for different lipidconcentrations. The collapse to the samemaster curve of the normalized spectra in theintermediate-high q region is the fingerprint ofa local invariance. A detailed analysis of thespectra is underway, since it is considerablycomplex, but some qualitative features can bededuced in a preliminary way.

0.01

0.1

1

10

100

1000

104

0.001 0.01 0.1 1

I(q)/

q(Å -1 )

volume fraction increase

For the lowest volume fractions the spectrafollows the grouping DLPU~DLP-MixDLP-Adenosine (for the intermediate-low q region),meaning that self stacking (extensivelydisplayed by the Adenosine moieties also innatural polynucleotides) has a strong impacton micellar flexibility; the persistence length ofthe wormlike objects (connected to thebending modulus of the aggregate) that iscalculated by extrapolation to infinite dilution ishigher for the Adenosine interactions.Increasing the volume fractions differencesbetween spectra disappear, but veryinterestingly a pattern shows up in the high qregion for the adenosine derivative and for themixtures.These results are really interesting and furtherprogresses will be presented in due course.

165


H O2C

Sum

cor

rect

ed in

tens

ity chosenmatch

correctmatch

ÊXPERIMENTAL REPORT Proposal N° BIO-04-597Instrument V4Kinetics of protein adsorption on colloidsLocal Contact Dr. U. Keiderling

Principal Proposer: W.G. Bouwman, IRI, Delft Uni. of Technology Date(s) of ExperimentExperimental Team: J. Efimova, IRI-DUT

M.G.E.G Bremer, IRI-DUTU. Keiderling, TU Darmstadt, HMI Berlin

*2 - 4 October 2001


The development of new bone-seekingradiopharmaceuticals for the treatment of bonecancer requires a thorough investigation of apossible competition between the radiophar-maceutical molecule and blood plasmaproteins for adsorption sites on the bone.Successful treatment of bone cancer asks for aradiopharmaceutical, which has a higheraffinity for the bone surface than the plasmaproteins. The two most abundant plasmaproteins are human serum albumin. These twoproteins show certain differences: humanserum albumin is larger than lysozyme and iscalled a ‘soft’ protein, which is expected tochange its secondary structure after adsorptionon a surface. This ‘spreading’ of the adsorbedmolecule maximises the number of contactpoints on the bone surface. Lysozyme is calleda ‘hard’ protein because its three dimensionalstructure is expected to stay more or lessintact after adsorption. Before the affinities and maximum adsorbedamounts of proteins and radiopharmaceuticalscan be studied, the mechanism of theadsorption process itself has to be understood.Therefore we have decided to investigate theexact structure of the adsorbed protein oncolloid particles with SANS. As a substrate wedecided to use silicon dioxide. (Titaniumdioxide was considered, but solutions of TiO2were not stable due to the high density.) Byusing contrast matching between the SiO2particle and the solvent the scattering of onlythe adsorbed protein shell around the colloidcan be determined. This provides informationon the thickness of the adsorbed layer and theamount of material. These measurementshave been done with different proteinconcentrations and pH-values of the solvent.Unfortunately, the analysis of the contrastmatch measurements at the beginning of themeasurements went wrong. The total amountof scattering of SiO2 particles as a function ofthe composition of the solvent (H2O vs. D2O)was determined by looking at the total intensitydetected with the detector. With a more

accurate determination later at home in whichwas corrected with a mask for the beam stoparea and for the background we obtained adifferent value for the optimal matchingconditions as shown in the plot below.

As a consequence we performed all themeasurements with the wrong matchingconditions. The scattering was now mainlydominated by the SiO2 particles. This is clearlyshown in a plot of the scattering of the SiO2particle in D2O combined with the scattering ofa particle with adsorbed protein in a "contrastmatching" solvent. By scaling with a factor 25the two curves overlap completely.

So most of the information on the thickness ofthe adsorbed layers is completely hidden in thescattering of the SiO2 particles. A little bit ofinformation seems to be left in the intensity.From the intensity we might be able to deriveinformation on the amount of adsorbed protein.

0,00 0,05 0,10 0,15 0,20 0,25

0,1

1

10

SiO2 in D2O

Q, nm-1

I, cm-1

Si BSA, ph=8, c=4mg/ml

166


EXPERIMENTAL REPORT Proposal N° EF; SF3-5Instrument V4The nano-structure of magnetosomes

studied by SANS Local Contact A. Hoell

Principal Proposer: Armin Hoell, HMI - Berlin Date(s) of ExperimentExperimental Team: Armin Hoell, HMI - Berlin

Albrecht Wiedenmann, HMI - Berlin 3.4. –5.4. 2001


The ability of magnetotactic bacteria to orient andmigrate along geomagnetic field lines is based onintracellular magnetic structures, themagnetosomes, which consists of nano-sized,membrane bound crystals of magnetic ironmaterials [1-3]. The formation of magnetosomes isachieved by a biological mechanism that controlsthe accumulation of iron and the biomineralizationof magnetic crystals (in most cases magnetite) witha characteristic size and morphology withinmembrane vesicles.Nowadays, there are a lot of efforts to cultivatethese magnetotactic bacteria to produce and extractthe magnetosomes particles, which has proven to bedifficult. The mechanisms of magnetosomeformation might be relevant for the synthesis offerrofluids (FF) with designed properties, useable inmagnetic drug targeting, cell separation andhyperthermia. Chemical prepared FF’s havemagnetite core diameters up to 15 nm or larger than70 nm. The medical most interesting size range isexcluded. Therefore, magnetosomes with sizes ofabout 40 nm fill that size gap.This report focuses on our first SANS investigationof one very diluted magnetite magnetosomessample in a mixture of H2O-D2O extracted fromcultivated bacteria (Magnetospirillumgryphiswaldense). Measurements were done on theinstrument V4 using the polarisation optionSANSPOL [4] and applying a horizontal magneticfield of 1 T to the sample perpendicular to theneutron beam.In Fig. 1 the SANSPOL scattering curves and thederived nuclear scattering are shown. Caused by thevery low particle concentration, the statistics of thecurves are not good and we were unable to extractthe magnetic scattering curve. Obviously, the twocurves of different polarization states differ. Thesimultaneous fit of these curves (solid lines) yieldedcore-shell particles (magnetite surrounded by anorganic membrane) with the shown volume sizedistribution (Fig. 2) of an averaged core size of 15.6nm and a shell thickness of 4 nm. The volumefraction was calculated to some 100 ppm only.

0.1 10.1

1

10Magnetosomes in H2O/D2O

on polarization off polarization nuclear scattering fit results

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig.1: The SANSPOL scattering curves and theextracted nuclear scattering are shown. Thelines represent the derived structure model ofcore-shell particles with the distribution of

5 10 15 20 250.0

0.5

1.0

1.5

2.0

dw/d

D *1

0-26 [n

m-1]

R (magnetite core) [nm]

Fig.2: The volume weighted magnetite core sizedistribution.

Therefore, this experiment is an example, howsensitive is SANSPOL in the case of very lowconcentrated magnetic samples comparing withconventional SANS.

[1] Blakemore, R.P.: Science 190 (1975) 377-379.[2] Schueler, D.: J. Molec. Microbiol. Biotechnol.

1 (1999) 79-86.[3] Schueler, D.: Biospektrum 6 (2000) 445-449.[4] A. Wiedenmann, Mat. Science Forum,

312-314 (1999) 315-324.

167


EXPERIMENTAL REPORT Proposal CHE-04-0660Instrument V6Effect of Temperature on the Adsorption of

Lysozyme on a Silica Surface Local Contact R. Steitz

Principal Proposer: C. Czeslik, Universität Dortmund Date(s) of ExperimentExperimental Team: G. Jackler, Universität Dortmund

R. Steitz, Hahn-Meitner-Institut BerlinT. Gutberlet, Hahn-Meitner-Institut Berlin

October 1-8, 2001


Dissolved protein molecules adsorb at almostall interfaces. There are several applications ofthis adsorption phenomenon, such as solid-phase immunoassays for medical diagnostictests, biosensors, and immobilized enzymes inbioreactors. On the other hand, proteinadsorption at interfaces may also haveunfavorable consequences, e. g., bloodcoagulation caused by artificial implants orbiofilms on used contact lenses. Thus, anunderstanding of the protein adsorption processon a molecular level and a determination of thestructure of protein adsorbates are necessary tooptimize these applications or to preventadsorbed proteins if they are undesired

The main aim of this study was toinvestigate the relation between thethermodynamic stability and the degree ofadsorption of hen egg white lysozyme at thesilica/water interface. Instead of studyingdifferent proteins varying in stability, thestability of lysozyme was changed by varyingthe temperature, which has the advantage ofkeeping protein-surface interactions nearlyunchanged. In addition, the contribution ofadsorption-induced conformational changes tothe driving forces for the lysozyme adsorptionwas investigated.

Concentration profiles of lysozymeadsorbates at the silica/water interface havebeen determined at 23, 63 and 80 °C and asolution concentration of 0.09 mg mL-1 usingneutron reflectometry. At each temperaturethree reflectivity curves have been measuredapplying the contrast variation method (Fig. 1),in order to decrease the number of structureprofiles which are consistent with the data. Thereflectivities have been fitted globally on thebasis of a 4-layer model, Si-SiO2-adsorbate-solution.

The analysis of the reflectivity dataindicates that the degree of lysozyme

adsorption at the silica/water interface isstrongly increasing, when the temperature israised from 23 to 80 °C. Surface coverages of1.8 mg m-2 (23 °C), 3.1 mg m-2 (63 °C), and 5.5mg m-2 (80 °C) have been found. Thisobservation indicates an endothermic and thusan entropy-driven adsorption process. Raisingthe temperature has the effect of destabilizingthe native lysozyme structure. As a result,adsorption-induced conformational changesoccur, which will serve as an entropic drivingforce for the adsorption process. Althoughdissolved lysozyme is unfolding at 70 - 78 °C(pH = 7), the structure profile of the lysozymeadsorbate at 63 °C appears to be more similarto that at 80 °C than to that at 23 °C, whichsupports the conclusion that in the range of 23– 63 °C lysozyme molecules must undergomajor conformational changes uponadsorption. This finding is consistent with arecent fluorescence spectroscopy study, inwhich the temperature of unfolding oflysozyme was found to be decreased due toadsorption on silica particles [1].[1] C. Czeslik, R. Winter, Phys. Chem. Chem.Phys. 3 (2001) 235-239.

1.E-08

1.E-06

1.E-04

1.E-02

1.E+00

0.00 0.02 0.04 0.06 0.08 0.10Q / Å-1

refle

ctiv

ity

D:H = 100:0D:H = 80:20D:H = 66:34

Figure 1. Neutron reflectivity curves of thesilica/water interface with adsorbed lysozymemolecules at 63 °C. The curves have beenshifted vertically for clarity.

168

0,00 0,05 0,10 0,151E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

10

Ref

lect

ivity

q [Ang-1]

dPS_new_D2O_3 dPS_DMPC(d54), D2O, test dPS_DMPC(d54), D2O, test2 dPS_DMPC(d54), D2O, test3

EXPERIMENTAL REPORT Proposal N° Bio-04-608/663

Instrument V6Lipid bilayers adsorbed to the solid-liquid interface

Local Contact: I. Estrela-Lopis

Principal Proposer: Beate Klösgen, FU Berlin, Fachbereich Physik,Arnimallee 14, 14195 Berlin, Germany

Date(s) of Experiment:

Experimental Team: Thomas Gutberlet, HMI BerlinRoland Steitz, HMI Berlin, TU BerlinIrina Estrela-Lopis, HMI Berlin, MPI-KG Golm

06.03.2001-11.03.2001

Date of Report: 25.03.01First experiments on lipid membrane formation at the solid-liquid interface were performed at the HMI. The neutronreflectometry results are shown in Fig. 1. They prove thatSUVs (prepared from di-myristoyl-phosphatidyl-choline(DMPC) in pure water) fuse to a Si surface that is coatedwith hydrophobic polystyrene (PS). A stable sorption of ~1.5-3 bilayers and more than 90% areacoverage was formed within hours. Most interesting, thedevelopment of diffraction Bragg peaks super-imposed tothe reflectivity patterns was found when the lipid wasprecipitated from a less dilute vesicle suspension (~5%).This observation (see Fig.1) is attributed to the presence ofmultilamellar liposomes as developed by fusion of smallvesicles when they hit each other. The Bragg peaks aresignificant of a portion of such liposomes that happen to beloosely attached to the interface. This undesired feature waspermanent in the sense that the attached multilamellarobjects were not spontaneously integrated by formingadditional planar layers. However, the liposomes wereeasily removed by rinsing, and upon that the initialreflectivity pattern was essentially restored. Accordingly,the uniformly adsorbed layers originated from the smallunilamellar vesicles of the initial sonicated suspension, andthe are mechanically stable as they withstand the shearforces of the rinsing flux.Another feature shown in Fig. 1 is the effect of the differentneutron scattering length densities of D- and H- used tomatch the reflectivity contrast: the single deuterated PSlayer is well resolved if measured against air, but iscompletely indiscernible if measured against D2O. Only theadsorption of the protonated lipid layers restores a new,undulating reflectivity pattern. As an advantage of contrastmatching, the reliability of the data extracted from therespective curves is increased.Our latest results show that the presence of detergents in thevesicle suspension, even at very low concentration,completely prevents the deposition of lipid layers onto thepolymer (see Fig.2). The monolayer that was observedadsorbed onto the PS cushion was not, even after longexposure times, covered by an additional bi-layer. Modelcalculations show that this single mono-layer is not uniform,maybe composed of an irregular mixture of lipid anddetergent.

The experiments performed as yet suggest the followingconclusions: A hydrophobic polymer sheet can serve as a soft

cushion for the deposition of single lipid bilayers.

Fig. 1: Adsorption of lipid layer(s) onto a deuterated PScushion; lipid: DMPC from 5% vesicle suspension.

Fig. 2: Reflectivity patterns taken during the deposition ofdeuterated lipid (DMPC-d54) onto a Si-support coveredby deuterated PS (dPS). In D2O, the reflectivity shouldresemble the black curve of Fig. 1. The observed patternsshow the presence of a protonated moiety at the interfaceconsisting of a detergent with admixed lipid molecules

The condensation of a uniform lipid monolayer and a(few) bilayers is not supported by the presence ofmulti-lamellar liposomes, and it is impossible frommicelles

Contrast matching provides valid modeling of thestructures (p.a. in the case of layers composed ofmixtures from protonated detergent and deuteratedlipid)

0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,181E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1 d-PS+DMPC/D2O

R

efle

ctiv

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q [Ang-1]

d-PS/air d-PS/D2O d-PS+DMPC after rinsing

169


EXPERIMENTAL REPORT Proposal N° *EFInstrument V6 *Binding of Aß (25-35) to a supported lipid

layer by neutron reflectometry Local Contact*R. Steitz

Principal Proposer: Silvia Dante, TU Darmstadt and HMI Date(s) of ExperimentExperimental Team: Thomas Hauß, HHU Düsseldorf and HMI

Thomas Gutberlet, HMIRoland Steitz, TU Berlin and HMI

*08.-14.10.2001

Date of Report: *31.01.2002

We have intensively studied the interaction ofthe neurotoxic ß-amyloid peptide Aß (25-35) byneutron diffraction and we were able to locate theC-terminus of the peptide in the core of thephospholipid bilayers, in the case of stacked lipidmultilayers. In order to gain further information onthe adsorption of Aß in/on lipid membranes, we arecurrently trying to simulate as close as possiblephysiological conditions. For this purpose, wetested the feasibility of neutron reflectivityexperiments on lipid layers obtained via fusion ofsmall unilamellar vesicles to a polymer-coatedsubstrate. This method is particularly appealing forour purpose, because under optimum conditions, ahybrid biomembrane, consisting of a polymeradsorbed lipid monolayer, resembling a softmembrane surface with an aqueous interface, anda free floating lipid bilayer in the fluid state isobtained. After equilibrium is reached, Aß can beinjected in the aqueous medium and the changes inthe reflectivity curve can be monitored.

The contrast scenario of the neutron reflectivityexperiment was chosen such as to highlight theprotonated peptide, Aß. Fig. 1, top curve shows thereflectivity of the interface of the spin-coatedpolymer film of deuterated polystyrene, d-PS, on asilicon block against the pure D2O subphase. Asexpected, the Kiessig interference fringes of thepolymer film are almost completely suppressed duethe lack of contrast at the polymer/liquid interface.The situation changes drastically – and the d-PScoating (292 Å) becomes visible – upon dis-placement of D2O against H2O (Fig. 1, secondcurve from top). Fig.1, third curve from top showsthe reflectivity of the polymer/liquid interface ninehours after injection of a solution of smallunilamellar vesicles of deuterated lipids (d54-DMPC) in H2O (0.58 mg/ml) into the liquid volumeof the sample cell. From the shift of the minimapositions of the Kiessig fringes towards low Q it isobvious that a condensed d54-DMPC monolayer(17 Å) was formed at the surface of the d-PScoating via fusion of the vesicles. No furtherincrease in thickness was found after establishmentof the DMPC monolayer. The polymer supportedlipid layer was almost invisible against D2O (Fig. 1,fourth curve from top). Figure 2 shows thereflectivity curves of the Si/d-PS/d54-DMPC/D2Ointerface before (top) and after injection of Aß into

the liquid subphase (bottom). As can be seen

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mainly the amplitude of the Kiessig oscillationincreased while there was no significant change ofthe minima positions. This proofs that Aß is notadsorbed to but inserted into the polymer supportedlipid layer.

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EXPERIMENTAL REPORT

Investigation of hydration eect on the lamellar structureof Stratum Corneum

Proposal N BIO 01-1077

Instrument V1

Local Contact

T. Hau


26. 11. - 13. 12. 2001Principal Proposer: Theodore Steriotis, NCSR Democritos, GreeceExperimental Team: Theodore Steriotis, NCSR Democritos, Greece

Georgia Charalampopoulou, NCSR DemocritosThomas Hau, Heinrich-Heine-Universitat Dusseldorf


The primary barrier to transdermal diusionresides in stratum corneum (SC), the thin out-ermost layer of the skin. SC hydration state isone of the most important factors that determinethe rate of percutaneous permeability. Despiteits great importance, the actual mechanism ofwater-SC interaction is yet unresolved. To thisend, the membrane neutron diraction methodwas employed aiming to reveal important struc-tural details of porcine SC and ultimately en-able the localization of water molecules in thetwo phases of the tissue, providing an insight ofthe mechanism of water sorption on SC. This hasbeen a long eort and up to now two preliminaryexperiments have been performed on V1. In therst one (BIO 01-874, 2-6 March 2000) we fo-cused on determining the optimum experimentalconditions (sample orientation, sample environ-ment, experimental set-up) and therefore a seriesof measurements on fully hydrated skin sampleswere performed. A slice of stratum corneumwas allowed to equilibrate in excess D2O con-ditions in a special constructed aluminum cell,where full contact with liquid D2O was continu-ous throughout the experiment. The excessivelydeuterated sample revealed a strong diractionpeak, located at Q=0.10 AA1, which corre-sponds to a periodicity of 62.8 A. Although ex-pected, the second order peak appeared only asa hint. In the second eort (BIO 01-938, 6-20November 2000) a modied cell was used and asa result the cell background and incoherent scat-tering from D2O were minimised. In this case,the main peak was at Q=0.09 A1, which corre-sponds to 69.8 A in real space, and the secondorder was clear. This shift of the peak towardslower Q implied that excess hydration distortsto some extend the organisation of the lamellarstructure. It was the primary aim of the current

experiment (BIO 01-1077), to examine whetherthe shift of the main diraction peak and ulti-mately its disappearance is a general trend oroccurs as a characteristic of the specic samplesused in the previous experiments. The biologi-cal variability of SC was tested by using humanepidermis samples originating from ve dier-ent donors. All samples were exposed to vapourand excess D2O conditions for dierent time pe-riods up to 22 h. A special cell, which couldaccommodate a stack of two or three SC lay-ers and was constructed in such a way that theneutron beam passes through a thin layer of Aland D2O, was used. By performing subsequent2 scans we were able to monitor the kineticsof the hydration process. It was again observed,and for all tested samples, that the main peakis progressively shifted towards lower Q with ex-posure time. The prolonged hydration resultsin a smooth diraction pattern. We can thusconclude that the bilayers do swell under excessdeuteration and the lamellar disruption is an ex-isting mechanism. In addition a preliminary lo-calisation experiment was performed by equili-brating the best behaving sample with a 20 %H2O/D2O mixture. The intensity of the mainpeak was reduced to the 78 % of that recordedat the measurement of the same sample equili-brated with D2O vapours.

171


EXPERIMENTAL REPORT Proposal N° OTH-01-994Instrument E9A comparative study of crystal structure

of dinosaur and resent animal bones Local Contact Dr. D.M.Toebbens

Principal Proposer: Prof. Sh. Gerbish, National Unversity of Mongolia Date(s) of Experiment 14.05.-18.05.2001

Experimental Team: D.M. Toebbens, HMI, BerlinD. Sangaa, National Unversity of MongoliaG. Batdemberel, Mongolian Technical University


IntroductionBone has a complex hierarchical structure,which despite much investigation, is still notwell understood [1]. Bone is a compositematerial of collagen and slightly impurehydroxyapatite. The c-axes of the apatitecrystal and the collagen fibres are preferntiallyoriented [2].This work is devoted to the comparativestudies on crystal structure of fossil and resentbones (dinosaur, sheep and skin of egg).Domestic animals, whose bones were studied,lived throughout Mongolia. But dinosaurs,whose remains were found in the Gobi desertseemed to present Mongolia. The ages ofthese bones vary astronomical scales, from 50to 250 million years. It becomes interestingfrom the point of natural history and biologicalevolution, in particular [3,4].

ExperimentsThe experiments was done on the E9 highresolution powder neutron diffractometer. Bonesamples of dinosaur, sheep and skin of eggwere exposed to chemical thermal processingin order to isolate organic components. TheRietveld refinement codes FullProf are usedfor structure refinements.

ResultsAll diffraction peaks in the spectrum wereidentified within the hexagonal (sp.gr.P63/m)and cubic(sp.gr.Fd3m) structures. Thediffraction spectrums obtained as a results ofthe refinement is given fig.1. The refinedstructure data illustrated in table 1, 2, 3.

The basic hydroxyapatite (Ca5(PO4)3OH)structure is hexagonal with space group P63/m,while the values of their structural parametersoften depend on the chemical thermalprocessing. Fig.1: Observed, calculated and diffrerence pattern profile for

dinosaur, sheep bones and skin of egg.

172


Tab.1: Refined crystallographic data for dinosaur bone. (n-occupation factor, Biso(10-2 nm2) isotropic temperature factor).

Tab.2: Refined crystallographic data for sheep bone. (n-occupation factor, Biso(10-2 nm2) isotropic temperature factor).

Tab.3: Refined crystallographic data for skin of egg. (n-occupation factor, Biso(10-2 nm2) isotropic temperature factor).

As a result of the refinement all the threesamples consist of two phases. The first mainphase is hydroxylapatite Ca5(PO4)3OH (P63/m)and the second is calcium oxide CaO (Fd3m).For each samples the second phase hasdifferent element content and crystal latticeparameters but the same main structuralmodifications which may be connected withheat treatment of the samples. The chemicalformulas of a calcium oxide phase in dinosaursbones and egg skins are Ca3.2O2 and Ca3.09O2,correspondingly. However, the calcium oxide

phase in sheep bones corresponds to thechemical formula: CaO. It shows that in fossildinosaurs bones and egg skins as a results ofheat treatment at 8000C free calcium oxideappears in equal quantities. On the contrary, inegg skins was not observed thehydroxylapatite phase.

As a result of neutron diffraction studieswe can conclude that the main phase in all thethree types of the samples is hydroxylapatite.The method allows to determine exactlyhydroxyl anion (OH-) contents in the phase.This is the advantage of the method. The factthat the chemical formula of calcium oxidephase, educed in dinosaurs bones and eggskins is Ca3.09O2, does not corresponds to theexact valence balance of calcium and oxygenions. When the number of calcium ions in theformula is less than three the calculated bytheoretical modelling peaks differ havingshorter values in comparisions with theexperimental spectra peaks. But when thenumber of calcium ion equals to three thecoincidence of the theoretical andexperimental spectra was good. At this time R-factors for spectra refinement have values lessthan 5.4%.

Finally, we can conclude that these twokinds of bone samples have hydroxylapatiteCa5(PO4)3OH as the main phase. On thecontrary, in egg skins there is nothydroxylapatite phase, the main phase is CaO.But a calcium oxide phase appeared as thesecond phase in dinosaurs and sheep bonesonly after heat treatment.

Reference[1]. Weiner S, Traub W, Bone structure: from angstrom to microns, FASEB J 1992 Feb 1; 6(3): 879-85. [2]. G.E.Bacon., The healing of fractured bones, http://www.ill.fr/AR-96/pages/o3mater.htm[3]. G.Batdemberel, D.Sangaa, D.Chultem., An investigation of structure in fossil bone mineral using neutron scattering, P133-99, JINR, Dubna.1999.[4]. G.Batdemberel, D.Sangaa, D.Chultem, Homology in vertebrals bone mineral structure, P134-99.. JINR, Dubna. 1999.

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Instrument E9Neutron diffraction studies of crystal structure ofground squirrel’s bone

Local Contact Dr. D.M.Toebbens

Principal Proposer: D.Sangaa, National University of Mongolia H.Fuess Technological University of Darmstadt

Date(s) of Experiment 11.07.-13.07.2001

Experimental Team: D.M.Toebbens, HMI, Berlin D.Sangaa, National University of MongoliaG. Batdemberel, Mongolian Technical University


Introduction The aim of this investigation was to determinethe structural parameters of bone minerals ofthe ground squirrel. Bone is a compositematerial of collagen and slightly impurehydroxyapatite. This work is devoted to the comparativestudies on crystal structure of fossil and resentbones [1-2].

ExperimentsNeutron powder diffraction patterns have beencollected for the bone sample on the Fine-Resolution-Powder Diffractometer E9 using n aneutron wavelength of 1.5819 angstroms atroom temperature. Bone samples of groundsquirrel were exposed to chemical thermalprocessing in order to isolate organiccomponents.

Structure refinement and Results

The structure refinement was done by theRietveld method using FULLPROF program .All diffraction peaks in the neutron diffractionpattern were identified within the hexagonalhydroxyapatite (Ca5(PO4)3OH) (sp.gr.P63/m)and cubic calcium oxide CaO (sp.gr.Fd3m)structures. The diffraction spectrums obtainedas a results of the refinement is given Fig.1.The refined structure data illustrated in Table 1.

The basic hydroxyapatite (Ca5(PO4)3OH)structure is hexagonal with space group P63/m,while the values of their structural parametersoften depend on the chemical thermalprocessing.

Fig.1: Observed, calculated and difference pattern profile for ground squirrel bone.

Tab.1: Refined crystallographic data for ground squirrel bone. (n-occupation factor, Biso(10-2 nm2) isotropic temperature factor).

Reference[1]. G.Batdemberel, D.Sangaa, D.Chultem., An investigation of structure in fossil bone mineral using neutron scattering, P133-99, JINR, Dubna.1999.[2]. G.Batdemberel, D.Sangaa, D.Chultem, Homology in vertebrals bone mineral structure, P134-99.. JINR, Dubna. 1999.

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EXPERIMENTAL REPORT Proposal N° MAT-01-741 and MAT-01-773 (Cont.)Instrument E3Determination of Residual Stress by ND in

6061Al-15 vol%SiCw Composites with DifferentWhisker Orientation/Distribution Local Contact A. Pyzalla

*

Principal Proposer: Gonzalez-Doncel, Gaspar, CENIM Date(s) of ExperimentExperimental Team: Fernández Serrano, Ricardo, CENIM

Bruno, Giovanni, HMIGonzalez-Doncel, Gaspar, CENIM

*22-30 July, 2001

Date of Report: *January 2002

Abstract

The determination of residual stresses, RS, in6061Al-15vol%SiCw composites was carriedout to correlate them with whisker orientation,distribution and aspect ratio. The compositeswere obtained by a powder metallurgical, PM,route and consolidated by extrusion at fourdifferent temperatures, Text. This is the mainparameter affecting the whisker orientation/distribution; an increase in Text leads to anincreasing whisker alignment with extrusionaxis. The results of the sin2

plots account fora non-hydrostatic stress state in allcomposites. This is expected because of thedeviatoric component of the RS tensorgenerated by the whisker geometry. The RScan explain the Strength Differential Effect,SDE, observed in uniaxial testing (tensile vs.compressive behaviour) of these composites.

Conclusions

RS are generated in the quenching processfrom the solid solution process (520ºC) prior tothe ageing treatment, and the extrusiontemperature (when lower than the solidsolution mixing temperature) can be seen tohave little influence on RS. The tension andcompression strength differences, SD/2 are ingood agreement with the ND measurementsand calculations with a modified Eshelbymodel, which takes into account the orientationdistributions of whiskers. The anomaly shownby the C45 material can be associated to theinhomogeneous whisker distribution (clustersor bands) observed.

a)

b)

Fig.1- strain, , vs sin2 curves for all the

investigated samples. (a) matrix, (b)reinforcement. The difference between thestrains measured at = 0° and = 90° isproportional to the RS that causes the SDE.The hydrostatic stress contribution in the SiCmay be related to the choice of the unstrainedmaterial.

175

EXPERIMENTAL REPORT Proposal N° MATInstrument E33D-Gauge Calibration Standard for FEM Residual

Stress Simulation of Welded Thick PlatesLocal Contact Dr. A. Pyzalla

Principal Proposer: Prof. Dr-Ing. U. Dilthey, ISF/RWTH Aachen Date(s) of ExperimentExperimental Team: Dipl.Ing.M.Kretschmer, ISF/RWTH Aachen

Dr. G. Buno, HMI, Berlin 5.22- 13.11.00

Date of Report: 20.02.01The aim of this project has been the determinationof a comprehensive three-dimensional residualstress field for welded plates. These data shall assistin obtaining a comparison as well as a calibration ofthe FEM-residual stress simulation. By means ofconventional stress measuring methods (drill-holemethod, x-ray diffraction) only the determination ofthe surface stress is possible, for a comprehensiveresidual stress simulation, however, the overallstress state has to be taken into consideration.Therefore an applicable 3D-standard gaugemeasure for FEM-residual stress simulations ofthick plates has to be determined within the scopeof this project.Apart from new findings as regards the stress stateof thick plates, the results shall serve the purpose ofcalibration measures for FEM simulations. Theresults of the FEM analyses can be adjustedcomparatively easy with surface measurements allright, but, up to the present, the number ofsufficiently exact measurements in part thicknessthat have been carried out is still too low. Duringthe course of this experiment two different weldspecimen with identical dimensions were tested. Onthe one hand, a TIG-welded specimen with thefollowing parameters U=19V, I=302A, shieldinggas: helium was used, and, on the other hand, aSAW-specimen with the following parameters:U=37.5, I=455A, weld flux: OK flux 10.71. Forboth welds, plates with the following measurementswere used: Steel S460M, length 400mm, width200mm, thickness 10mm. Specimen A (TIG): ascan in a plate depth of 5mm was carried out inlengthwise direction to the weld (10 measuringpoints). Then a measurement series (4 measuringpoints) was made through-thickness direction.Specimen B (SA): unfortunately only the depthscan (5mm) could be carried out (9 measuringpoints). Figure 1 shows the depth scan in a platedepth of 5mm at specimen A. The measuring results are, during the further courseof the project, to be processed towards a 3D stressfield. Then, metallurgical and mechano-technological tests are to be carried out with theobjective of a comprehensive documentation of thespecimen. Figure 2 shows the hardnessmeasurement series in accordance to the depth scanat specimen A. In the further course of the project,

the results are to be compared with the results fromthe FEM-residual stress simulations and are then tobe applied as standard gauge measures forstatements about the stress state through-thicknessdirection.

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ur zweckmäßigen Definition von Eigenspannungenärterei-Technische Mitteilungen 28 (1973) 3, S.201-211auk,V.; Macherauch, E.:ie zweckmäßige Durchführung röntgenographischerpannungsermittlung (RSE): Hauk,V.; Macherauch, E. (Hrsg.): Eigenspannungen undastspannungeneiheft der HTM, 1982, S.1-19. Dilthey, U.Reisgen, M.Kretschmeromparison of FEM simulations to measurements ofsidual stresswes for example of a welded plate: a state-of-the-artportodelling Simul. Mater. Sci. Eng. 8 (2000) S. 911-926

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EXPERIMENTAL REPORT Proposal N° MAT-01-893Instrument E3Residual Stress determination in MMC components

before and after mechanical testingLocal Contact G.BRUNO

Principal Proposer: Emmanuelle Girardin, Università di Ancona Date(s) of ExperimentExperimental Team: Emmanuelle Girardin, Istituto di Scienze Fisiche

Adrian Manescu, Istituto di Scienze FisicheGiovanni Bruno, HMI

12/12-22/12/2000


Two kinds of MMC samples were investigated:AA6061 reinforced with Alumina and AA2009reinforced with SiC with a wavelenght of 1.37012Å. The following Bragg peaks have been chosen :(311) of SiC at 2 = 62°(311) of Al at 2 = 68°(226) of Al2O3 at 2 = 82°.

Alumina Reinforced Sample.Residual stress measurements have been performedon billets (diameter 90 mm, height 32 mm)AA6061 and AA6061 + 20%Al2O3 The measurement have been performed in themiddle of the height of the billet.In the non-reinforced billet, the average stress isaround 80 MPa in the three directions and constanton the diameter of the billet.In the reinforced billet, we noticed a strong textureof the Al2O3. Moreover, due to the presence of anMg2O spinel at grain boundaries around the Al2O3we had difficulties to isolate a diffraction peak ofAl2O3. The measurements give a quite high error onthe alumina peak position due to the low signal-to-noise ratio. It seems that the macrostress isnegligible and that the thermal mismatchmicrostress is the more important contribution tothe total stress. In the aluminium matrix it liesaround 80 MPa and in the alumina reinforcingphase it is around 200 MPa, compressive.

Silicon Carbide reiforced samples.Residual stress analyses have been performed onextruded tubes AA 2009 + 25% SiC, one asextruded, one after standard T4 treatment.

Figure 2. Geometry and size of thsample, reinforced with -

As extruded sample:The macro stress lies between 100 anall directions. The main contributiostress is the thermal mismatch microsin the aluminium phase around 50 MSiC phase around -200 MPa. Macrostresses are displayed in aluminium matrix.

T4 sample:The macro stress is a little lower, dtreatment, around 80 MPa. The maito the total stress is the thermmicrostress which is, in the alumaround 80 MPa and in the SiC phasMPa.

In both samples the level of stress is the thickness of the tube (from the upthe inner one) and there is no bbetween the as-extruded and the treat

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Instrument E3Influence of physical and technologicalparameters on residual stresses in net-shaped

steel crown gears Local Contact A. Pyzalla

Principal Proposer: E.GIRARDIN, University of Ancona, Italy. Date(s) of ExperimentExperimental Team: A.GIULIANI, University of Ancona, Italy.

A.MANESCU, University of Ancona, Italy. 15-23 July 2001 (E3).

Date of Report: 17 September 2001

Since the 1980s, the automotive and aeronauticalindustries have shown the feasibility of usingparticulate reinforced MMC structural componentssuch as rear wheel hubs (automotive application) andstringers and shafts (aeronautical application). Theexperiment here described have been carried out in amore general research, aiming to develop a set ofcomplementary models to optimise the formingprocess of these MMC components. We studied theeffect of the forming process on the residual stressstate of the real components mentioned above.

The automotive components are made of 6061+20%Al2O3 and are forged.

As MMC are highly heterogeneous materials, residualstresses are present in the microstructure prior tomacroscopic loading, and vary with the macroscopicloading level and the temperature of the specimen orcomponent.

The measurements have been carried out at the E3Diffractometer of the HMI- Bensc (Germany) on afinal component after forging (473°C) and thefollowing condition (560°C x 2h, Quenching water60°C, Artificial ageing 177°C x 8h). 6 measuringpoints have been chosen as shown in figure 1, in thecentral part of the component (the first point is 2 mmunder the surface) and in the border (all 3 points are1.5 mm under the surface, and the last one 1.5 mmfrom the border).

The chosen wavelength was =1.37 Å, in order toinvestigate the Bragg peaks:

- (311) for Al (2 = 69°) - (10 10) for Al2O3 (2 = 68,1°)

The gauge volume was 2x3x2 mm3 (determined by aslit system: 2x2 mm2 on the incoming beam, and 3x20mm2 on the diffracted beam) for Al2O3. and Al.

Determination of the unstrained interplanar distance(d0):

- Al2O3 reinforcement: powdersample.

- Al 6061 matrix: powder sampleobtained from an ingot.

But in the case of Al matrix, we encountered an otherproblem. As demonstrated previously by micrographicexamination of the 6061 + 22% Al2O3 material, wenoticed a strong texture of the Al peaks. We tried other peak acquisitions by tilting the sampleof some degrees from the exact 2 position, but theresults were the same. In these conditions, we determined experimentally theresidual stresses in the principal directions but theywere affected by large experimental errors, even afterlong time acquisitions. In any case the obtainedresults are in agreement with those obtained oncomponents of the same shape and similar state andmeasured on other experiment cycles in other RsearchCenters. A more detailed analysis of the obtainedresults on this sample is still in progress .

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EXPERIMENTAL REPORT Proposal N° MAT-01-957Instrument X1Residual Stress Determination in near-net Shape

Forming Specimen obtained by Thermal Spraying Local Contact Tobias Poeste

Principal Proposer: Emmanuelle Girardin, Univ. of Ancona,Italy Date(s) of ExperimentExperimental Team: Adrian Manescu, Univ. of Ancona,Italy

Nicolae Markocsan, ISIM Timisoara,Romania 18.03 – 26.03. 2001


The new technologies used in the field ofaerospatial, aeronautical or automotiveindustries require new high-tech materials.These materials, in the most cases, are difficultto process by "classical" processes. One of the new processing methods is the near-net shape forming by thermal spraying, but thisprocess could induce a high level of residualstress. One of the most significant problems informing net-shape is the generation of residualstresses upon spraying that limit both the finalsize of the tubes as well as their post-spraymechanical integrity under applied mechanicaland thermal stresses.The validation of the theoretical analysis andmathematical models were performed by X-raydiffraction measurements. The experiment hasbeen carried out using the sin2

technique onyttria partial stabilised zirconia conicalspecimens, the measurements being done intwo directions: axial and tangential (Fig.1)

Fig. 1 Geometry of the samples

Investigations have been made for evaluationof residual stress levels induced by the mode ofmandrel removing. Three different way ofmandrel removing has been used: by cooling,by melting and by chemical dissolving.

The investigated Bragg peak was (302) forZrO2 (2=118°). It was used the CoK

radiation, =1.7889 Å. We used a circular sliton the X-ray beam with 1 mm in diameter.The used ( ,) angles were:2 angles: 0° and 909 angles: 0°, 28°, 36, 42, 50.

We did not observe a big difference from theresidual stress point of view in the threeanalysed samples, although it seems that thecooling method lead to higher level of residualstress. The possible explanation of lower residualstress for melting and dissolving method are, inboth cases, the development of the alreadyexistent cracking network. Therefore, theconclusion we draw is that cooling method ispreferable. Of course, further theoretical and experimentalinvestigation (such as neutron diffractionmeasurements to determine bulk stresses)should be performed in order to confirm thisconclusion and to develop better unbondingmethods.

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EXPERIMENTAL REPORT Proposal N° EF-SF3-05*Instrument V4 *Determination of Microstructure during

Shear Stresses Local Contact *A. Wiedenmann

Principal Proposer: M. Modigell, RWTH Aachen, A. Wiedenmann Date(s) of ExperimentExperimental Team: L.Pape , RWTH Aachen

A. Wiedenmann, HMIP. Strunz, HMI

*21.5-23.5 2001 6.-9.8. 200112.-17.11.2001

Date of Report: *

The goal of the experiments is the determination ofstructure changes during shear stresses in semi solidmetal alloys. To set up the experimental environ-ment, aqueous polymer suspensions, with a knownparticle diameter and solid fraction, were used asmodel suspensions.

A test-cell, consisting of two concentric cylinders,is implemented into a rheometer. The resulting slitis 1.5 mm wide. The cell is working like the Searle-principle, meaning that the inner cylinder is rotatingto impress a certain shear stress, while the outer oneis fixed. Both cylinders are composed of syntheticquartz.

Within the first measurement period the test-cellwas investigated in terms of transmission, applica-bility and stability. The empty cell was centred inthe neutron beam and was operated without anyrotation. The scattering values and the transmissionof the empty cell were detected using a collimationfrom 4 m up to 16 m The detector distance variedfrom 1 m up to 16 m. The same procedure was per-formed with the neutron beam passing the tangen-tial part of the slit.Afterwards the experiments were repeated with theinner cylinder rotating at a speed of 100/s to getinformation about changes in transmission andscattering.

Our second measuring period was used to investi-gate the scattering behaviour of two aqueous poly-mer suspensions, one from the industry with a meandiameter of around 35 nm and a solid fraction ofaround 35 % and one synthetic solution generatedat the RWTH Aachen with a mean diameter of80nm and a solid fraction of ~40%. It was expectedthat the suspensions get a certain order or, respec-tively, a change in microstructure would occurwhile they are sheared. The new microstructurewould result in a change of viscosity and should berecognized by small angle neutron scattering.Both samples were sheared for several hours withshear rates of 0/s, 1/s, 100/s and 600/s. The collimation and the detector distance were alsochanged within their range. Even though a smallchange in viscosity could be observed for both sus-pensions, the scattering results did not show any

increase in intensity. Each scattering angle resultedin the same intensity value, no matter which shearrate was adjusted.After processing the raw data, one could at leastverify the mean diameter of ~80 nm measured bySANS.

During the third measuring period we studied amodified synthetic suspension produced at theRWTH Aachen. Compared to the first one, thissample was de-ionised to ensure a change in orderwhile shearing.The sample was again exposed to shear rates from0.2/s up to 850/s. The rheological measurementspointed out, that the viscosity changed with eachshear rate, whereas the SANS just observed an al-teration in microstructure at certain points.

On the one hand the scattering picture shows astructure of concentric rings, on the other hand weobserved six peaks in intensity arranged in a hex-agonal way.

As a fact, this behaviour is reversible, which meansit is unattached whether the shear rate increased ordecreased.

These results are probably related to a transforma-tion from a 2-dimensional order, where layers aresorted in a row, to a 3-dimensional hexagonal lat-tice.

181


EXPERIMENTAL REPORT Proposal N° MAT-01-956Instrument X1PHASE TRANSITION DURING 4-POINT BENDING

OF NITI SHAPE MEMORY ALLOY Local Contact T. Pöste

Principal Proposer: W. W. Schmahl Date(s) of ExperimentExperimental Team: H. Sitepu, Ruhr-Universität Bochum

S. Falkenhagen, Ruhr-Universität BochumU. Trombach, Ruhr-Universität Bochum

13.7-23.7. 2001


We investigated the reaction of superelastic NiTiwith 50.7 at.-% Ni to 4-point bending with x-raydiffraction. The alloy was subjected to solutionannealing at 850C for 0.9 ks followed by waterquenching. Subsequently the material was aged at atemperature of 400C for 15 min.

A strip of 50 mm x 10 mm x 2 mm was cut fromthe sample. The surface was carefully polishedmechanically and finally with electrochemicalmethods.

Fig. 1

Fig. 1 shows the x-ray diffractograms taken withCo-K radiation on the X1 diffractometer.

On the 4-point bending attachment of X1, the loadis applied by two bearings 30 mm apart, and thecounter-bearings are at a distance of 15 mm. Theattachment allowed observations only above 65° 2-Theta. A minimal force of 37 N was applied to fix thespecimen on the instrument. This load wassufficient to induce the formation of someextremely textured martensite on the surface, asbecame visible by the peak at 99° 2-theta. With aforce of 2500 N the limits of the superelasticplateau in the stress-strain curve had been reached:When the load was reduced to 50 N, the martensitealmost completely transformed back to austenite

and the final diagram was similar to the initial onetaken at 37 N.Fig. 2 shows calculated diffractograms for therelevant data range for austenite (top) andmartensite (bottom) assuming no preferredorientation.

Fig. 2

With the missing low-angle data due to the limited2-theta range, and complete evaluation of thediffractogram is difficult.The apparent change in relative intensities of themartensite with loading indicates strong changes inthe texture of the martensite grains at the surfacelayer of the sample.

2000

3000

4000

5000

6000

7000

8000

9000

65,00 70,00 75,00 80,00 85,00 90,00 95,00 100,00 105,00

182


EXPERIMENTAL REPORT Proposal N° MAT-01-989Instrument E9PHASE STATE OF NiTi SHAPE MEMORY

ALLOYS WITH TWO-STEP TRANSITIONS Local Contact D. Többens/M. Tovar

Principal Proposer: W. W. Schmahl Date(s) of ExperimentExperimental Team: H. Sitepu, Ruhr-Universität Bochum

S. Falkenhagen, Ruhr-Universität BochumW. W. Schmahl, Ruhr-Universität Bochum

29.3.-7.4. 2001


Aim of the study was the determination of thephase state of a Ni-rich NiTi shape memory alloy ofnominal composition 50.7 at.-% Ni showing a two-step martensitic transition in the presence of Ni4Ti3precipitates in the microstructure. The alloy wassubjected to solution annealing at 850C for 0.9 ksfollowed by water quenching. Subsequently thematerial was aged at a temperature of 400C for 72ks where the precipitation of Ni4Ti3 particlesoccurs. The two-step transition is indicated in theDSC curve (Fig.1), and arrows in Fig. 1 point to thetemperatures where neutron diffractograms havebeen collected.

-100 -50 0 50 100-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

(b)

aged @400°C, 20 h

5 4 3

21

heat

flow

[W/g

]

temperature [°C]

Fig.1

Fig. 2 shows the observed and calculateddiffractogram with Rietveld-difference curve forthe Ni-rich NiTi shape memory alloy aged at 400°Cfor 20 hours. The data were collected at 21°C(arrow 4 in Fig. 1), where four phases are present.The small vertical bars below the profile representthe positions of the Bragg reflections of thesephases (from top to bottom: B2 - austenite, R-phase, Ni4Ti3, and B19’ - martensite).Table 1 gives the volume fractions of all phasesderived from Rietveld refinement for the 5diffraction experiments outlined in Figure 1 as wellas the volume fraction for the room temperaturestate determined by TEM (indicated by *).

Table 1Temp Volume fractions (%)(C) B19’ B2 R Ni4Ti3

Heating25 83.2 2.1 14.774 87.4 12.6

Cooling58 87.7 12.321 25.9 3.7 63.2 7.2, 3.01.3*

-28 85.5 1.2 13.3

Fig. 2

From the data we concluded, that in aged Ni-richalloys, the first DSC peak on cooling is not due tothe formation of the R-phase alone, and that the R-phase is associated with monoclinic B19' alreadybetween the two DSC peaks. The occurence of R-phase in these samples can beattributed to at least two mechanisms: (i) the Ni4Ti3precipitates make the formation of B19’ moredifficult by representing obstacles to hightransformation strains, (ii) the formation of R-phaseis moreover favoured, because R-phase variantsaccomodate coherency stresses around the Ni4Ti3particles and thus minimize overall strain energy. The work has been published [1].During the beam time, neutron diffractograms of anumber of other NiTi alloys were collected at lowtemperatures.[1] H. Sitepu, W.W. Schmahl, J. Khalil Allafi, G.Eggeler,A. Dlouhy, D.M. Többens, M. Tovar.Scripta Materialia (2002) in press.

183


EXPERIMENTAL REPORT Proposal N° MAT-01-1068Instrument E9R- AND B19' PHASE COEXISTENCE IN NI-RICH

NiTi SHAPE MEMORY ALLOYS Local Contact D. Többens/M. Tovar

Principal Proposer: W. W. Schmahl, Ruhr-Universität Bochum Date(s) of ExperimentExperimental Team: H. Sitepu, Ruhr-Universität Bochum

13.-23.7.2001


The transformation of a Ni-rich NiTi alloy ofnominal composition 50.7 atomic percent nickelwhich was solution annealed, water quenched andaged at 500C for 20 hours was investigated byneutron diffraction. The material shows a two-steptransition on cooling with differential scanningcalorimetry peaks at 18C and 7C. On heating, asingle peak occurs at 43C. The aging leads to theformation of Ni4Ti3 precipitates in the micro-structure, and in the presence of the precipitates themartensitic transformation occurs from the cubicB2 phase via the R-phase to B19 martensite.However, the first peak on cooling is not due to theformation of R-phase alone. Below the peaktemperature, R-phase is present along with someB19 and with residual B2 and the precipitates. Thesecond peak is related to the transformation of R-phase and B2 to B19. This result confirms ourearlier conclusions which were obtained for thesame alloy aged at 400°C for 20 hours [1].

Fig.1

Fig. 1 shows the DSC curves for the solution-annealed (a) and the aged material (b, c). Curve (c)is an enlargement of the cooling cycle of (b), (d)shows the volume fractions of the phases asdetermined by neutron diffraction with Rietveldanalysis. The diffractograms were taken at thetemperatures indicated with arrows in Fig. 1 (c).

Table 1. Volume fraction of all phases derivedfrom Rietveld refinement

Temperature Volume fraction (%)(C) B19 B2 R Ni4Ti3

On cooling40.1 (arrow 1) 93.4 6.620.3 (arrow 2) 43.1 49.7 7.217.8 (arrow 3) 8.8 31.2 52.4 7.615.2 (arrow 4) 32.4 26.7 33.0 7.89.4 (arrow 5) 83.3 10.0 6.66.7 (arrow 6) 88.4 5.2 6.43.4 (arrow 7) 88.8 3.7 7.1

-10.2 (arrow 8) 89.5 3.4 7.1

One possible explanation of this result is based on ascenario when homogeneously distributed Ni4Ti3

particles affect the Ni concentration of thesurrounding B2 matrix. Here the chemical inhomo-geneity and the difference in nucleation barriersbetween R-phase (small transformation strain) andB19 (larger transformation strain) rationalizenormal (one step and two steps) and unusual(multiple steps) transformation behavior [2].Another possible explanation is related to hetero-geneous precipitation of Ni4Ti3 particles near grainboundaries. Here the multiple step martensitictransformation can be related to this microstructuralheterogeneity [2]. The work has been published [3].

[1] H. Sitepu, W.W. Schmahl, J. Khalil Allafi, G.Eggeler,A. Dlouhy, D.M. Többens, M. Tovar.Scripta Materialia (2002) in press.[2] G. Eggeler, J. Khalil Allafi, A. Dlouhy, X. RenX., submitted to J. Physique (Proceedings ofICOMAT 2002)[3] H. Sitepu, W.W. Schmahl, J. Khalil Allafi, G.Eggeler,A. D. M. Többens, submitted to J.Physique (Proceedings of ICOMAT 2002)

184



Instrument E2Crystal and Magnetic Structure of Ni2MnGa MagneticShape Memory Alloy

Local Contact S. Danilkin

Principal Proposer:Name, AffiliationV. Gavriljuk, Inst. for Metal Physics, Kiev, UA Date(s) of Experiment

Experimental Team: N. Glavatska Inst. for Metal Physics, Kiev, UAS. Danilkin, D. Hohlwein, R. Schneider, HMIA. Skomorokhov, Inst. for Physics and Power Engineering,Obninsk, Russia

27.03 –9.04.2001

Date of Report: 15 May 2001

Ferromagnetic Ni49Mn30Ga21 alloy showsmore than 5% strain under applied magneticfield in the martensitic phase at roomtemperature. This effect is caused by thepreferential growth of martensitic variantsfavorably oriented in relation to appliedmagnetic field. Induced strain is limited by thetetragonality ratio, c/a, of martensite crystallattice [1]. In the present measurements withdiffractometer E2 we studied Ni49Mn30Ga21alloy with temperature of the martensitictransition, Tm, close to the room temperature.The aim of the measurements was to study: (1)modifications of the crystal structure duringaustenitemartensite (cooling) andmartensiteaustenite (heating) phasetransitions; (2) temperature dependence of thelattice parameters and tetragonality ratio inmartensite during cooling and heating in thetemperature range close to Tm (290-320K); (3)correlation between magnetic andcrystallographic structure in the austenite phaseby comparison of the diffuse scattering in theferromagnetic and paramagnetic phases.

Results Austenitic phase has cubic structure Fm3m

with lattice parameter 0.583 nm. The twinnedmartensite was defined as the tetragonal phasewith five-layered modulation. Unit celldimension were found to be a = b = 0.420, c =0.558 nm at 297K.

Strong temperature dependence of the latticeparameters in martensite was observed(Fig. 1, 2). Correspondingly the tetragonalityratio, c/a, in martensitic phase decreases duringheating from 0.925 at T=4 K to 0.946 atT=300 K. Transformation of the austenitephase to martensite starts insensibly at

temperature about 2 degrees below themartensitic point and then occurs very sharplyat martensitic transition temperature.

18 19 20 21 22 23 24 25 26 27 28 29 300

50

100

150

200

(107)

(020)

(105)

(103)

T=293 KT=301 K

T=276 K

T=116 KT=57 KT=4 K

T=203 KT=253 K

Inte

nsity

0 2 ThetaFig. 1. Neutron diffraction patterns of Ni49Mn30Ga21single crystal taken at temperatures 4 – 300K.

0 100 200 300

-0 ,10

-0 ,05

0,00

R

elat

ive

para

met

er

Temperature, K

a=aT-a 300 c=cT-c300

Fig. 2. Relative change of the cell parameters inmartensite with temperature.

[1]. R.C.Handley, J. Appl. Phys., 83, 3263(1998).

185

MAT-01-1018 // Nadejda // 22.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N°MAT-01-1018Instrument *E2Change in crystalline structure of Ni2MnGa alloy

under magnetic field Local ContactS.Danilkin

PrincipalProposer: V.Gavriljuk, Institute for Metal Physics, Kiev, UA Date(s) of

ExperimentExperimental N.Glavatska, G.Mogilny, Institute for Metal Physics, Kiev

S.Danilkin, D.Hohlwein, Hahn-Meitner-Institut, BENSC 28.10-04.11.2002

12.01.2002

Present investigation concerns of the neutrondiffraction study the structure and an effect of amagnetic field on martensite structure in the singlecrystal ferromagnetic Ni2MnGa alloy showed large(more than 5%) strain induced by a magnetic field atroom temperature. Magnetic shape memory effect(MSME) is caused by the preferential growth ofmartensitic variants favorably oriented in relation toapplied magnetic field. MSME is limited bytetragonality.

Results1) Studied alloy has temperature of the martensitictransition Tm=300K. Austenitic phase has cubicstructure Fm3m with lattice parameter 0.584 nm.The reciprocal space for martensite set on neutrondiffraction data (Fig.1) shows that 4 additionalreflexes accompany the principal reflections inmartensite. These additional spots are situatedbetween the main spots into 5 equal parts andindicate the 5-layered structure (Fig.1). The real unitcell of studied martensite in the terms of modulatedstructure can be determined as orthorhombic 5-layered with lattice parameters, calculated fromneutron diffraction data: а=0.421 nm, b=0.562 nm,c=2.105 nm at 296K. The simulated unit cell for 5-layered structure is shown in Fig.2. The shufflingmodulation system is (100) [010] in bct coordinates.If to deduce martensite lattice from the fundamentalspots ignoring 5-layered structure, the martensiteunit cell can be defined as bct with space groupI4/mmm and lattice parameters а=b=0.421 nm,c=0.562 and c/a=1.335.2). The martensite lattice parameters change withtemperature: a cell parameter changes less then0,003 nm under cooling from 304,2K down 4,16K,while c cell parameter decreases strongly - morethen 0,010 nm with the temperature decrease.Combined change in a- and c- cell parameters (in theterms of bct lattice) effects on the martensitetetragonality c/a which is changed during coolingdown to 4K for 2.32%.3) Effect of the external magnetic field up to 0.6T onmartensite structure in Ni2MnGa single crystal wasfirstly observed with neutron diffraction in-situ

study (Fig.3). The specimen was aligned to have(001) plane coinciding with scattering plane, themagnetic field was applied normal to it Themagnetic field causes redistribution of martensitevariants (Fig.3). The value of the martensite variant,which is in congruence with direction of easymagnetization, decreases in the studied surface withrise of the magnetic field magnitude (Fig.3).

Fig.1. Reciprocal space (hk0) for single crystallineNi2MnGa as neutron diffraction study result at 296K. a

b

c

Fig.2. Unit cell of the martensite lattice in studied singlecrystal Ni2MnGa simulated from neutron diffraction data.

20 25 30 35 0

20

40

60

80

107

020105

103H=0.6TH=0.4TH=0.2TH=0T

o2Theta Fig.3. Neutron diffraction in-situ study an effect of theexternal magnetic field on martensite structure in Ni2MnGasingle crystal (fragment), T=280K. Indexes are given interms of 5-layered structure.

186

ef_25 // brandt // 21.03.rr Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EFInstrument V4SANS determination of the morphological changes in

'- precipitate microstructure at high temperatures inRe-containing Ni-base single crystal superalloy

Local Contact P. Strunz

Principal Proposer: P. Strunz, HMI Berlin, NPI Řež Date(s) of ExperimentExperimental Team: D. Mukherji, TU Braunschweig

R. Gilles, TU DarmstadtA. Wiedenmann, HMI Berlin

08. - 13.05.2001


In the frame of investigation of microstructuralchanges in Ni-base superalloys at hightemperatures [1,2], '-precipitate morphology of Re-containing superalloy SCA433 was investigated.The heat treatment of the sample reported here(denoted 5b¼) prior the SANS experiment wascomposed of two steps: 1285°C/4h/ air cooling and1100°C/0.25h/ air cooling.

The data was collected for the sample-to-detectordistance equal to 16 m and = 19.4 Å. Due to thelow flux of the neutron source at such wavelength, itwas possible to measure without the beam-stopwhich usually protects the 2D position-sensitivedetector against overloading by non-scatteredneutrons in the primary beam [2,3].

The data collected in situ during the increase of thetemperature (standard ILL furnace used) wereevaluated by a special procedure [3] suited foranisotropic data treatment. Both measured andfitted data at some of the temperatures aredisplayed in the figure (d/d in a logarithmic scaleis shown: color maps are the measured data andequiintensity lines denote the fit of the optimummodel). The sample was single crystal, thereforethe anisotropic structure of the patterns at lowertemperatures can be observed.

The positions of interparticle-interference maxima

give the center-to-center distance of ' precipitates.Their mean size and distance increase above1000°C, but the question was if it increaseshomogeneously in the whole sample or not.The results of the detailed data evaluation indicatethat this increase does not happen homogeneouslyin the whole irradiated volume. While theprecipitates are homogeneously distributed at hightemperatures in some parts of the sample, they areeither completely dissolved or they coalesced andbuilt larger ones in the other parts.

The minimum in the total scattering probabilitybetween 1200 and 1300°C corresponds to thesolutionizing window of the alloy.

[1] R. Gilles, D. Mukherji, P. Strunz, A.Wiedenmann, J. Roesler, H. Fuess, Proc. Int.Conf. THERMEC'2000, Las Vegas, USA, Dec.2000, CD-ROM: (Special Issue of J. of Mat.Proc. Tech. 2001), Eds. T.Chandra, K.Higashi,C.Suryanarayana & C.Tome, Elsevier Science(ISBN 0 08 044026 6), Section D7, Vol 117/3

[2] P. Strunz, D. Mukherji, R. Gilles, A.Wiedenmann, J. Rösler and H. Fuess, J. Appl.Cryst. 34, (2001), 541-548.

[3] Strunz P., Wiedenmann P., Gilles R., MukherjiD., Zrník J. and Schumacher G., J. Appl. Cryst.33 (2000), 834-838.

-0.003

0.000

0.003

0.006

-0.006 -0.003 0.000 0.003 0.006

Qy (

Å-1)

-0.003

0.000

0.003

0.006

-0.006 -0.003 0.000 0.003 0.006

23°C-0.006 -0.003 0.000 0.003 0.006

-0.006 -0.003 0.000 0.003 0.006

1000°C

-0.006 -0.003 0.000 0.003 0.006

-0.006 -0.003 0.000 0.003 0.006

1080°C

-0.006 -0.003 0.000 0.003 0.006

-0.003

0.000

0.003

0.006

-0.006 -0.003 0.000 0.003 0.006

-0.003

0.000

0.003

0.0061120°C

-0.006 -0.003 0.000 0.003 0.006

-0.003

0.000

0.003

0.006

Qy (

Å-1)

Qx (Å-1)

-0.006 -0.003 0.000 0.003 0.006

-0.003

0.000

0.003

0.006 1160°C

-0.006 -0.003 0.000 0.003 0.006

Qx (Å-1)

-0.006 -0.003 0.000 0.003 0.006

1200°C

-0.006 -0.003 0.000 0.003 0.006

Qx (Å-1)

-0.006 -0.003 0.000 0.003 0.006

1240°C

-0.006 -0.003 0.000 0.003 0.006

-0.003

0.000

0.003

0.006

Qx (Å-1)

-0.006 -0.003 0.000 0.003 0.006

1340°C

187


EXPERIMENTAL REPORT Proposal N° MAT-04-638Instrument V4Determination of the morphological changes in '- '' co-

precipitates after high temperature exposure by SANSLocal Contact P. Strunz

Principal Proposer: D. Mukherji, TU Braunschweig Date(s) of ExperimentExperimental Team: P. Strunz, HMI Berlin

D. Del Genovese, TU BraunschweigR. Gilles, TU Darmstadt

16. - 19.08.2001


Iron rich superalloys like IN706 are extensivelyused for gas turbine disc applications at hightemperatures and for long durations.

The development of IN706 or other similaralloys has promoted interest in theprecipitation reactions which occur when Tiand Al are partially or completely replaced byniobium. In the presence of high Nb/(Ti + Al)ratios, a metastable phase forms preferrentiallyat low to medium temperatures. This phase(called '') has composition Ni3Nb with a body-centered tetragonal structure. It forms as fineplatelets or as a co-precipitate with the 'precipitates (i.e ' at the core and '' on top ofit) and produce extremely effectivestrengthening. Unfortunately, the metastable ''tends to be replaced by a Ni3Ti basedhexagonal phase called after long exposureat temperatures above 650°C.

Overageing the microstructure severelyrestricts the use of these alloys to their fullpotential. Many investigations in the past havetherefore been conducted to study theoverageing process by conventional methods.The morphology of the '/'' co-precipitates inthe bulk material as well as theirtransformation to needle shaped precipitatesin IN706 can be monitored by SANS.

Specimen

Solutionannealing stabilisat

ion

'/'' stabilisation

DA 980°C/2h - 720°C/8h cool-1K/min 620°C/8h

ST 980°C/2h 850°C/3h 720°C/8h cool-1K/min 620°C/8h

IDA-1 980°C/2h - 720°C/8h waterquenched

IDA-2 980°C/2h - 620°C/8h waterquenched

MST 980°C/3hcool-4K/min

820°C/10h 720°C/8h cool-1K/min 620°C/8h

In the present experiment, characterisation ofprecipitate morphologies in IN706 alloy after

five different heat treatments was carried out.These heat treatments (see the table) werespecially designed to bring out differentcombination of precipitates in the alloy – e.g.one sample had only ’ and ’’ co-precipitates,while another had additional precipitation of phase at grain boundaries. Further the

precipitation could be controlled either withingrains or at grain boundaries.

From the SANS measurement (see the figure),it was immediately possible to determine acertain tendencies: e.g., -stabilisation heattreatment (850°C/3h) causes ’/’’ co-precipitates to grow and to be more distant(characteristic distance without -stabilisationheat treatment was 30 nm while with it already80 nm). Another sample differently exposed to’/’’-stabilisation heat treatment exhibited largedifference in characteristic distance as well:the 100°C increase in the temperature of theheat treatment (from 620°C to 720°C) causedincrease of the characteristic distance from

approximately 5 nm to 20 nm.

The detailed evaluation and interpretation ofthe data is being carried out.

0.01 0.1 1 10

0.1

1

10

100

1000

10000

IDA-2

IDA-1

DA

ST

MST DA ST IDA-1 IDA-2 MST

Q (nm-1)

d/d

(cm

-1sr

-1)

188



Instrument E9Misfit measurements of W – rich Ni-basesuperalloys Local Contact

D. Többens

Principal Proposer: Ralph Gilles, TU Darmstadt Date(s) of ExperimentExperimental Team: D. Mukherji, TU Braunschweig

P. Strunz, HMI Berlin,J. Rösler, TU BraunschweigD. Többens, HMI Berlin

15.8. - 20.8. 2001


Single crystal Ni-base superalloys are precipitationhardened by ordered Ni3Al based intermetallicphase (), which are coherent with the matrix phase(). Both (fcc) and (primitive, L12 structure)phases have cubic crystal structure with only asmall difference in their unit cell size, giving rise toa lattice misfit. The shape, configuration andorientation of precipitates are determined, in part,by the coherency strain arising from this latticemismatch between the two phases. The evolution ofprecipitate morphology at high temperatures underthe application of an uniaxial load (a phenomenonknown as rafting) is also very much dependent onthe precipitate-matrix misfit value (). The misfit is defined as:

)(5.0 '

'

aa

aa

,

where a is the unit cell size of the unconstraint and lattices, respectively. is positive when the unit cell is larger than that of phase.The lattice parameter values of and ’ phasesdetermined by XRD or ND are only global averagevalues over the entire gauge volume [1]. Especially,neutron measurements allow to receive informationover a huge volume and to find out thehomogeneity of a sample and if present grainboundaries etc.. As one example of our misfitmeasurements with neutrons a tungsten (W) richNi-base superalloy is presented.

Fig 1: (100) and (200) neutron reflection. Anadditional broad peak in (200) was necessary forgood profile fitting.

Tab. 1 Listing of d values and misfit of W sample.

Peak

No.

[hkl] d () d ( ) misfit

neutrons1 100 3.58712 200 1.7914 1.7946 0.002 3 300 1.1948

Synchr.1 100 3.61152 200 1.8247 1.8073 -0.0103 111 2.0738 2.0840 0.005

X-ray2 100 3.59113 200 1.8002 1.7938 - 0.0044 111 2.0826 2.0709 -0.006

Reference1.) R. Gilles, D. Mukherji, P. Strunz, B. Barbier,

D.M. Többens, J. Rösler and H. FuessNeutron- , X-ray- and electron diffraction measure-ments for the determination of / ’ lattice misfitin Ni-base superalloysApplied Physics A, in print.

59.0 59.5 60.0 60.5 61.0 61.5

0

20000

40000

60000

80000

100000

Tungsten alloy(200)

Cou

nts

2 [°]

28.0 28.5 29.0 29.5 30.0

0

2000

4000

6000

8000

10000

Tungsten alloy(100)

Coun

ts [n

]

2

189

EXPERIMENTAL REPORT Proposal N° MAT-04-632Instrument V4In situ observation of the formation of '

precipitates in the Ni-base superalloy Local Contact P. Strunz

Principal Proposer: R. Gilles, TU Darmstadt Date(s) of ExperimentExperimental Team: P. Strunz, HMI Berlin, NPI Řež

D. Mukherji, D. del Genovese, TU BraunschweigR. Gilles, TU Darmstadt, A. Wiedenmann, HMI

28.10. – 02.11.2001


The control of the morphology and distribution ofthe ’ precipitates is essential for Ni-basesuperalloys to achieve optimal mechanicalproperties. It can be realized through several stepsof heat treatment at high temperatures. Kinetics ofprecipitate growth is traditionally studied bymicrostructural observations on samples quenchedfrom the aging temperature. This procedure is,however, not ideal as further precipitation can notbe totally suppressed. SANS has been proved [1,2]to be a well-suited in-situ technique, which is ableto provide real morphological information at theaging temperature.

The current experiment uses a newly developedRe-rich single-crystal superalloy. In situ SANSinvestigation of the ’-precipitate growth in as castsample Re81SX at elevated temperatures ispresented here.

The first step of the applied heat-treatmentprocedure (solutionising at 1340°C) was intendedto dissolve all precipitates including ’. Furtheraging treatment at 1100°C (4 hours) is essential forcontrolling of the morphology and distribution of thenewly created ’ precipitates (important forachieving optimal mechanical properties).

The data was collected with a standard ILL furnacefor several geometries. The results reported hereare from the measurement with sample-to-detectordistance equal to 16 m and = 19.4 Å.

The used temperature profile can be seen in Fig. 1.This figure reports also the total scatteringprobability obtained by the fit of anisotropic data [3].

As expected, the scattering substantially decreasesafter the fast temperature increase over 1300°C.However, it increases again gradually towards highvalues during the holding period. Increase of therelative volume fraction of large inhomogeneities(Fig. 2) is the main cause of such behavior. Itindicates that either the temperature was not highenough to solutionize the largest precipitates or thatincipient melting occurred. In the first case, the slowdiffusion of some element (most probably Re, whichpartitions practically exclusivelly in matrix) couldcauses their gradual growth and/or gradualincrease of their scattering contrast at the usedsolutionizing temperature. If the second explanationis valid, it would indicate gradual growth of incipientmelting islands with time.

The second step of the heat-treatment (holding at1100°C) produces significant amount of medium-size precipitates (see Fig. 2), but their mostsignificant part is created only on cooling to roomtemperature. It implies that the cooling rate is asignificant factor determining the final precipitatemicrostructure.

Further data treatment is being carried out.

[1] P. Strunz, D. Mukherji, R. Gilles, A.Wiedenmann, J. Rösler and H. Fuess, J. Appl.Cryst. 34, (2001), 541-548.

[2] D. Mukherji, P. Strunz, R. Gilles, J. Rösler, A.Wiedenmann and H. Fuess, Applied Physics A(ICNS 2001 Proceedings), accepted

[3] Strunz P., Wiedenmann P., Gilles R., MukherjiD., Zrník J. and Schumacher G., J. Appl. Cryst.33 (2000), 834-838.

0

0

0

Tem

pera

ture

(°C

)

00:00 04:00 08:00 12:00 16:00 20:00 24:00 28:00 32:00 36:000

200

400

600

800

1000

1200

1400

Tem

pera

ture

(°C

)

Temperature profile

time (hours)00:00 04:00 08:00 12:00 16:00 20:00 24:00 28:00 32:00 36:00

0.0

0.2

0.4

0.6

0.8

relative volume fraction: medium-size precipitates large inhomogeneities

rela

tive

volu

me

fract

ion

Fig. 2. Determined relative volume fractions of large(>5000 Å) and medium-size (4500 Å) precipitates.

00:00 24:000

200

400

600

800

100

120

140

Temperature profile

time (hours)00:00 04:00 08:00 12:00 16:00 20:00 24:00 28:00 32:00 36:00

0.5

0.6

0.7

0.8

0.9

1.0

Scattering probability

Scat

terin

g pr

obab

ility

Fig. 1. Temperature profile and determined scatteringprobability for Re81SX as cast sample.
MAT-04-0632 // brandt // 23.03.rr Seite 1 von 1
190


EXPERIMENTAL REPORT Proposal N° MAT 01-1070*Instrument E9Thermally induced martensitic transformation

in NiTi and CuAlMnZn SMA Local Contact Daniel Többens

Principal Proposer: Petr Šittner, Petr Lukáš Date(s) of Experiment

Experimental Team: Václav Novák, Inst.of Phys., Na Slovance 2,Prague, Czech RepublicDimitar Neov, Nuclear Phys.Inst., Řež near PragueMichael Tovar, HMI Berlin

2 - 7.10.2001


Internal stresses in transforming shapememory alloys (SMA) have been studied indetail at dedicated stress/strain diffractometersin NPI Rez in dependence on externalthermomechanical loading. Of course,additional knowledge of structures of individualphases is of great importance in this case. Thestructural studies on mechanically andthermally treated NiTi and CuAlMnZn SMAwere then realized at E9 instrument.Commercial Ni-49.5Ti [at.%] alloy in the formof polycrystalline bar (5mm in diameter, 15mmlength) was heated in the cryostat up to 368K.The diffraction spectra were collected duringthe specimen cooling down to T=202K atintermittent temperature points: T=300, 292,287, 272, 237 and 202 K. Such a temperaturerange covers all phase transformations in NiTi.In the case of cold worked/aged or solutiontreated NiTi alloy an intermediaterhombohedral R-phase appears during theforward martensitic transformation [1]. Ittemporary coexists with the cubic (B2)austenite and monoclinic (B19’) martensite.The R-phase is in many aspects uniqueamong other phases detected in the SMA. Itsstructure is created by a rhombohedraldistortion (angle α) along one of the 4equivalent <111> directions of the cubic lattice(see Tab. 1). More details and results arereported elsewhere [2]. The B2→Rtransformation is basically observed indiffraction experiment as splitting of the mainaustenite reflections into two (110A, 111A,112A, 012A) or three (122A) R-phase peaks andincreasing of their separation with decreasingtemperature (Fig.1). FullProf program withincorporated strong fiber <111> texture wasused for data fitting.Tab. 1. R-phase SG P 3 (hexagonal settings) [1]T=292K T=285K T=272Ka=7.3535Å a=7.3411Å a=7.3306Åc=5.2582Å c=5.2662Å c=5.2759Åα=89.57° α=89.44° α=89.32°

(011

)

(111

)

(2-1

2)(3

00)

(003

)(4

-21)

(033

)(1

41)

(5-4

2)

(7-5

1)

0

2000

4000

6000

8000

10000

R-phase T=272K observed calculated

inte

nsity

20 40 60 80 100 120 140-505

2 theta / deg

Fig.1 Fitted curve of NiTi SMA.

Similar experiment was done at Cu–basedSMA. Cu-10Al-5Mn-5Zn (wt.%) specimenshave been measured in powder form in orderto avoid the strong texture influence. Austenitephase at T=300K was fitted with L21 orderedBCC structure (SG F23) with lattice parametera= 5.861Å. Evolution of the volume fractions ofmartensitic phase with decreasing temperaturehas been observed in the temperature interval195-297 K, covering thus the transformationregion of Ms=239K and Mf=223K (detreminedby DSC measurement).

References [1] T.Goryczka, D. Stróż, H. Morawiec, Proc. XVIII

Conf.of Appl. Cryst. 4-7 Sept.2000 Poland,World Scientific (2001), p.251-254.

[2] P.Lukáš, P.Šittner, D.Neov, V.Novák, D.LugovoyM.Tovar, ECRS6 10-13 Jul. 2002, Portugal.

191

EXPERIMENTAL REPORT Proposal N° MAT–04-0652Instrument V4SANS study of microstructural changes in Ni-base

superalloy due to long-time thermal exposureLocal Contact Pavel Strunz

Principal Proposer: J. Zrník, Technical University Košice Date(s) of ExperimentExperimental Team: P. Strunz, HMI Berlin

P. Horňák, Technical University KošiceV. Vrchovinský, Technical University Košice

04.-06.10.2001


The polycrystalline nickel base superalloyEP742 is widely used for gas turbine discs. It issupposed to resist the high temperature andstresses, which induce significant materialdegradation and damage. As the mechanicalproperties of the nickel base superalloys arethe result of their two-phase structure(coherent ‘ precipitates in phase matrix), thestability of the ‘ phase is a prerequisite of thealloy mechanical properties stability.

The previous SANS experiment (MAT–04-509)has been successful to detect themorphological changes of ‘ precipitates inthermally exposed superalloy EI698VD [1].The aim of the presented SANS experimentwas similar: to clarify the creep deteriorationproperties of the nickel base superalloy EP742 which was thermally exposed prior creepfor different time (up to 52000 hours) at twodifferent temperatures (430°C and 650°C). Theother experimental techniques (lightmicroscopy, TEM and SEM) used formicrostructure analysis were not sufficient toprovide an evidence of creep deterioration [2].

Fig. 1 displays measured cross-sections of thesamples exposed at 650°C). Systematicchange of the scattering curve with expositioncan be observed. The detail of the cross-sections in the interparticle-interference peakregion can be observed in Fig. 2.

For EP742, the (‘) precipitates are bigger thanin case EI698VD and their distances arecorrespondingly larger (approx. 1800 - 2100Å). There are not so huge changes of ’microstructural parameters with the expositionlength as for EI698VD (e.g. their averagedistance increases approximately by 10% onlyfor the EP742 sample exposed for 28000hours). The exception is the sample exposedfor 52000 hours, which exhibits unexpectedchange of scattering cross section with respectto the preceding ones. Further investigationsshould determine an origin of such behavior(an artifact or a realistic property of the metal).

SANS patterns clearly revealed (in contrast toEM) morphological changes of ’-phaseprecipitates. Dependence of microstructure onthe thermal exposition is, however, significantlylower for EP742 than for EI698VD superalloy.A detailed data evaluation is being carried out.

[1] P. Strunz, J. Zrník and A. Wiedenmann: inEUROMAT 2001 Conf. Proc., CD-ROM, AIM 2001,paper No. 84.[2] Zrník J., Vrchovinský V. and Berčák M.: in Proc.of 8th Int. Conf. on the mechanical behaviour ofMaterials ICM8, May 1999, Vol II. MaterialsProperties 4, 676-681.

INITIAL_STATE 650°C / 2000 h 650°C / 5000 h 650°C / 8000 h 650°C / 10000 h 650°C / 25000 h 650°C / 28000 h 650°C / 52000 h

0.01

1000

10000

d/d

(cm

-1sr

-1)

Q (nm-1)Fig. 2. Detail of the cross-sections in theinterparticle-interference peak region.

Fr

1E-3 0.01 0.1 10.01

0.1

1

10

100

1000

10000

100000

Q-4

INITIAL_STATE 650°C / 2000 h 650°C / 5000 h 650°C / 8000 h 650°C / 10000 h 650°C / 25000 h, no creep 650°C / 28000 h 650°C / 52000 h, no creep

d/d

(cm

-1sr

-1)

Q (nm-1)ig. 1. Cross-sections in the whole measured Q-ange for samples exposed at 650ºC.
192


Instrument V4SANS Investigation of Magnetic Ni Crystals in anAmorphous Ni-P Alloy Local Contact

A. Hoell

Principal Proposer: D. Tatchev, Universität Rostock / Inst. Phys.Chem. – Bulg. Acad. Sci., Bulgaria Date(s) of Experiment

Experimental Team: D. Tatchev, Inst. Phys. Chem. – Bulg. Acad. Sci.A. Hoell, HMI Berlin 05 April 2001

Date of report 20 April 2001

The aim of the test experiment was to estimate themagnetic scattering effect from as prepared andthermally treated amorphous Ni-P alloy at roomtemperature and magnetic flux density up to 1.1 T.

Two alloys with hypoeutectic compositions of 17and 18 at.% were investigated. The thermally treatedsample of Ni83P17 alloy was annealed at 250oC for 3hours, but those of Ni82P18 for 9 hours. The samplesthickness was about 0.1 mm. SANS measurements wereperformed at wavelength of 0.6 nm. The polarizedneutron capability of the V4 instrument [1] was used. Tocheck the magnetic saturation of the presumablysuperparamagnetic particles in the thermally treatedNi83P17 alloy the corresponding sample was measured atdifferent magnetic flux density values in the range of 0 -1.2 T.

Figures 1 and 2 show the scattering curves of the asplated and thermally treated Ni83P17 alloy. The magneticcontrast variation [2] has almost no effect on the curvesof the as plated alloy obviously due to the absence ofmagnetic particles. However, magnetic structuredevelops during annealing and this is well demonstratedin Figure 2. The preliminary evaluation suggests abimodal particle size distribution in accordance with theprevious SAXS experiments. The comparison of thenuclear and magnetic scattering terms indicates astructure of a magnetic core in a nonmagnetic shellsimilarly to the findings obtained for some glasses [3, 4].The Ni82P18 shows no magnetic particles even after 9hour heat treatment.

The dependence of the integrated intensity of thescattering curves for the two polarization directions isshown in Figure 3. The saturation magnetization is

obviously reached at flux densities higher than 0.6 T. Thus the use of SANS with polarized neutrons is

clearly a suitable technique to study the magneticstructure of the precipitating particles in amorphous Ni-Palloys.

0.1 1

0.01

0.1

1

10

100

1000

Ni83P17 heat treated

at 250oC for 3 hours

I(Q) [

cm-1sr

-1]

Q [nm-1]

Neutron polarization parailel to H antiparailel to HScattering term nuclear magnetic

Figure 2 Scattering curves of Ni83P17 alloy heat treated at 250oC for3 hours.

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Ni83P17 heat treated

at 250oC for 3 hours

Neutron polarization parallel to H antiparallel to H

Inte

grat

ed in

tens

ity [c

m-2sr

-1]

Magnetic flux density B [T]

Figure 3 Magnetic flux density dependence of the integratedintensity for the two directions of the neutron polarization.

[1] T. Keller, T. Krist, A. Danzig, U. Keiderling, F.Mezei, A. Wiedenmann, Nucl. Instr. Meth. Phys. Res. A451 (2000) 474[2] A. Wiedenmann, J. Appl. Cryst. 33 (2000) 428[3] U. Lembke, A. Hoell, R. Kranold, R. Müller W.Schüppel, G. Goerigk, R. Gilles, A. Wiedenmann, J.Appl. Phys. 85 (1999) 2279[4] J. Marchin, A. Wiedenmann, I, Skorvanek, Physica B276-278 (2000) 870

0.1 11E-3

0.01

0.1

1

10

100

1000

Ni83P17 as prepared

Neutron polarization parallel to H antiparallel to HScattering term nuclear magnetic

I(Q) [

cm-1sr

-1]

-1
Q [nm ]
Figure 1 Scattering curves of as obtained Ni83P17 alloy.




Instrument V4Magnetic Correlation Length In NanocrystallineFe89Zr7B3Cu1 Local Contact

A. Hoell

Principal Proposer: O. Moze, Modena Univ. (I), K. Suzuki, J. Cadogan,UNSW (Australia) Date(s) of Experiment

Experimental Team: E. Agosti, O. Moze, Modena Univ. (I)J. M. Cadogan, UNSW, AustraliaA. Hoell, A. Heinemann, HMI

6-10 Dec, 2001


Nanocrystalline Fe-rich materials comprisingbcc -Fe nanocrystals embedded in anamorphous matrix phase possess excellentsoft magnetic properties, as the grain size(typically of the order of 10 nm) is shorter thanthe magnetic correlation length Lex. The originof the magnetic softness arises from asubstantial reduction of the magneticanisotropy K1. The RAM (Random MagneticAnisotropy Model) predicts that in thenanocrystalline regime, D << Lex, the magneticcorrelation length scales as;

321

2

ex DKAL

where A is the exchange stiffness constant. Amore realistic situation is that where ananocrystalline soft magnet contains aconsiderable amount of residual amorphousphase (with exchange stiffness Aam) in additionto the crystalline part (exchange stiffness Acr).In this more sophisticated 2-phase model(Suzuki and Cadogan, Phys. Rev. B 58 (1998)pp 2730-9), the magnetic correlation lengthscales as;

4amcr

21

ex )A/A/D(KDL

where Pure Fe nanocrystallites indeed showthe predicted Lex D-3 scaling (Loffler et al,Phys. Rev. Lett. 85 (2000) pp. 1990-3), butvery little is currently known about the actualtemperature dependence of Lex in 2-phasematerials. For this purpose, SANS has beenemployed to determine the temperaturedependence of Lex in a prototypical 2-phasenanocrystalline material, Fe89Zr7B3Cu1. Thissample has been characterized by Mossbauerspectroscopy and bulk magnetizationmeasurements. The exchange correlationlength is predicted to change dramatically inthe region 20°C to 90°C. Measurements were

performed on V4 in the polarized neutronmode, in order to accurately separate thenuclear and magnetic SANS. Measurementswhere performed in 10 ° C intervals from 20° Cto 200 °C. SANS cross sections at 20 and 60°C are displayed below. Data analysis isunderway and we intend to present this workat the forthcoming SAS Conference, Venice,August, 2002.

0 ,1 10 , 0 1

0 ,1

1

1 0

1 0 0

0 ,1 10 ,0 1

0 ,1

1

1 0

1 0 0

I(q)

q ( n m -1 )

M a g n e t i c , 2 0 ° C

N u c l e a r 2 0 ° C

0 ,1 10 , 0 1

0 ,1

1

1 0

1 0 0

0 ,1 10 , 0 1

0 ,1

1

1 0

1 0 0

I(q)

q ( n m - 1 )

M a g n e t ic , 6 0 ° C

N u c le a r 6 0 ° C

194


EXPERIMENTAL REPORT Proposal N° MAT-04-649Instrument V4Dissolution and precipitation of NbC in Fe70Ni30Local Contact Pavel Strunz

Principal Proposer: N.H. van Dijk, IRI, TU Delft, Netherlands Date(s) of ExperimentExperimental Team: S.E. Offerman, IRI, TU Delft, Netherlands

S. van der Zwaag, TNW, TU Delft, NethrelandsJ. Sietsma, TNW, TU Delft, Netherlands

8-11 November 2001


A principle strengthening mechanism inhigh strength low alloy (HSLA) steels arises fromthe ultra-fine grain size developed during thermo-mechanical processing. Strain induced precipitationof NbC promotes a fine grain size during theaustenite (fcc-iron) to ferrite (bcc-iron) phasetransformation. A recently studied model alloyFe70Ni30 does not transform on cooling to roomtemperature. This makes it possible to study thesize distribution of strain induced NbC precipitatesas a function of the process conditions.

We have performed small-angle neutronscattering measurements (SANS) at the instrumentV4 on samples of the model alloy Fe70Ni30 andwith different concentrations of Nb. As the samplesare ferromagnetic at room temperature allmeasurements were performed at temperaturesabove the ferromagnetic transition temperature (TC

130 oC) in order to avoid magnetic domainscattering. In a previous experiment (MAT-04-552)we found that an applied magnetic field of 1.15 T isinsufficient to saturate the magnetisation ofFe70Ni30 at room temperature.

The studied Fe70Ni30 (0.08 wt.% C)samples with different Nb and Mo are all heated to1200 oC and subsequently deformed at 900 oC. Wemeasured the small angle neutron scattering from 5different samples at a temperature of T = 300 oC.An example of the scattering intensity as a functionof the wave vector transfer is shown in the firstfigure for the Mo containing sample with andwithout Nb. The influence of Nb is only observedin the lower Q range.

For 2 of the samples without Mo and withdifferent Nb concentrations we have studied thetemperature dependence of the scattered intensityfor 300 oC < T < 1300 oC. For increasingtemperatures the precipitates are expected tocoarsen and dissolve which leads to a gradualdecrease in scattered intensity. The last 2 figuresshow that the scattering at high Q is stronglytemperature dependent at relatively lowtemperatures, while the scattering at low Q is onlyaffected at relatively high temperatures. We expectthat the observed scattering is related to defects athigh Q and to precipitates at low Q.

0.1 10.01

0.1

1

10

100

T = 300 oC

Fe70Ni301.59 wt.% Mo

0.00 wt.% Nb 0.09 wt.% Nb

d/d

(cm

-1sr

-1)

Q (nm-1)

0.1 10.01

0.1

1

10

100 Fe70Ni300.09 wt.% Nb

T = 300 oC

T = 700 oC

T = 1100 oC

d/d

(cm

-1sr

-1)

Q (nm-1)

0.1 10.01

0.1

1

10

100 Fe70Ni300.03 wt.% Nb

T = 300 oC

T = 800 oC

T = 1100 oC

d/d

(cm

-1sr

-1)

Q (nm-1)

195


EXPERIMENTAL REPORT Proposal N° PHY-04-650Instrument: V4Structural phase transition on Fe-Pt alloysLocal Contact Armin Hoell

Principal Proposer: Thang D. Pham, Universiteit van Amsterdam, NL Date(s) of ExperimentExperimental Team: Thang D. Pham, Universiteit van Amsterdam, NL

E. Brück, Universiteit van Amsterdam, NLA. Hoell, HMI, BENSC, Germany

10-13 December 2001


1. IntroductionThe crystallographic structure of Fe-Pt alloys isFCC after quenching from high temperature.For the alloys of equal atomic composition, atransition from the FCC to FCT occurs duringthe annealing at low temperature. Thisstructural transition results in a strong increaseof the magnetic hardness of the alloys withhigh magneto crystalline anisotropy. Tounderstand the mechanism responsible for thehigh performance magnetic properties, in-situanalysis of the changing of microstructure andmagnetic structure during the phase transitionis important. In combination with an appliedmagnetic field, SANS is a useful technique tostudy the isotropic nuclear and the anisotropicmagnetic structures independently. Thedistributions and grain sizes of the magneticdomains of the FCC and FCT phases can alsobe analysed.

2. ExperimentalIn this study, 3 alloys with the composition asshown in Table 1, in both the as-quenched(AQ) and annealed (AN) state have been used.Table 1.Alloy AQ ANFe60Pt40 1325C, 1h 625C, 0.5hFe59.7Pt39.8Nb0.5 1325C, 1h 625C, 24hFe59.85Pt39.9Al0.25 1325C, 1h 525C, 24h

The SANS experiment were carried out on theinstrument V4 using the polarisation optionSANSPOL [1]. The samples were measured ina temperature range from 20C up to 400Cand an applied a horizontal magnetic field ofup to 1.1T perpendicular to the neutron beamdirection. The neutron wavelength was 0.6 nm.During the measurement, a two-dimensionalposition sensitive detector was placed at threedistances of 1 m, 4 m and 12 m to get ascattering vector range, Q, of 0.04nm-1 to3nm-1.

Using the empty Cd slit scattering did thebackground correction. The absolute calibra-tion was performed by measurements of thewater standard.

3. ResultsAs an example, Fig. 1 shows the final curves ofnuclear and magnetic scattering intensities inthe AQ state of the Fe59.7Pt39.8Nb0.5 alloy. Theresults are derived from all detector positions.

0.01 0.1 110-4

10-3

10-2

10-1

100

101

102

103

104

105

FePtNb alloy (AQ) nuc ; virgin state mag ; " nuc ; high temp, no field mag ; "

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig. 1 Measured SANS intensities are Shown as a function of Q.

We observe a pronounced nuclear andmagnetic scattering in the virgin state. Bothscattering parts are significantly decreased andthe shapes are changed in the paramagneticstate at high temperatures. Further analyses willbe continued in the coming time.This work is supported by the EuropeanCommission under the IHP Programme(project number 214, contract HPRI-CT-1999-00020) and the Dutch Technology Foundation(STW).Ref: [1] A. Wiedenmann, Mat. Science Forum,

312-314 (1999) 315-324.

196


EXPERIMENTAL REPORT Proposal N° EF-SF3-5Instrument V4H/D- contrast variation combined with

SANSPOL in Ferrofluids (I): Constituents Local Contact

Principal Proposer: Albrecht Wiedenmann, HMI Date(s) of ExperimentExperimental Team: Martin Kammel,

Armin Hoell, HMIAlbrecht Wiedenmann, HMI

19.03. - 27.03.0131.03. - 02.04.01

Date of Report: *

New biocompatible water-based ferrofluids withmagnetite, Fe3O4, as core and Laurin-acid andmarlipal as surfactants with potential medicalapplications have been prepared by Berlin HeartAG. In this series we investigated Ferrofluidssamples with the same magnetite cores diluted inthree different mixtures of H2O/D2O(composition, denoted as H0.2D1.8O, H0.6D1.4, DHO).Due to the different scattering length densities thenuclear contrast between solvent and compositeparticle is changed.Measurements were performed on the instrument,V4, using the polarisation option, SANSPOL [1].The SANSPOL intensities for two polarisationstates (I+(QH) and I-(QH)) are presented in Fig.1for the three solvents. (Symbols). All curves showthe characteristic feature for a density profilearound particles which is approximated by a core -shell model, as described in [2].

0.1 1

0.1

1

10

100

b)

a)x

D2O

Scatt

erin

g cr

oss-

secti

on [c

m-1

]

Q [nm-1]

0.9 0.7 0.5

0.1 1

0.1

1

10

100x

D2O

Scatt

erin

g cr

oss-

secti

on [c

m-1]

0.9 0.7 0.5

Fig. 1: SANSPOL curves of magnetite ferrofluidsin solutions with different H/D ratios are shown.The Intensities I-(QH)(open symbols) are given ina) and the Intensities I+(QH)(filled symbols) in b).

The actual H/D-ratio in the was determined fromthe incoherent background,as obtained at high Q.These H/D ratios agree well with the theoretical

values. The combination of polarized neutrons withthe H/D-contrast variation allowed to rule outvarious possible structural models. With thedifferent contributions shown in Fig. 2 we wereable to fit all six curves (Fig.1) simultaneously withone consistent set of parameters. This allows aprecise determination of size, size distribution,magnetic moment and compositions of core andshell.

0.1 110-2

10-1

100

101

102

103

Sc

atte

ring

cros

s-se

ction

[cm

-1]

Q [nm-1]

Fig. 2: The SANSPOL Intensity I-(QH) (opensymbols) of magnetite ferrofluids in H0.2D1.8O isshown. The solid line is the theoretical intensityresulted from the structure model. The fittedintensity consists of the following parts: grey dottedline: incoherent background, grey short dashed line:surfactant, black dotted line: core - shell particles,dashed line: magnetic aggregates.

[1]A. Wiedenmann, Physica B297(2001)226-233[2]A. Wiedenmann, A. Hoell, M. Kammel, ,

JMMM (2002) in press

197


EXPERIMENTAL REPORT Proposal N° EF-SF3-5Instrument V4H/D-contrast variation combined with

SANSPOL in Ferrofluids (II): Composition Local Contact*

Principal Proposer: Albrecht Wiedenmann, HMI Date(s) of ExperimentExperimental Team: Armin Hoell, HMI

Martin Kammel, HMIAlbrecht Wiedenmann, HMI

19.03. - 27.03.0131.03. - 02.04.01

Date of Report: *

In previous investigations we analysed thestructural properties of ferrofluids based onmagnetite, Fe3O4, with different types of surfactants[1]. The influence of the sample preparation on thestructure parameters is still unsettled. For theseinvestigation new sets of samples have beenprepared by the Berlin Heart AG. The coreconsisting of magnetite is stabilized againstcoagulation by coating with organic chainmolecules which act as surfactants [2]. Thesesurfactants consist of a bilayer of a dodecanoic acidand a C12 ethoxylated alcohol. Samples with four different concentrations andthree different H/D-ratios of the solvent have beeninvestigated together with the correspondingmixtures of pure surfactants. The results for thediluted case of about 1vol% Fe3O4 are describedbelow.We performed SANSPOL-measurement at theinstrument V4 to investigate their structure andcomposition, as well as the influence of theconcentration. A horizontal magnetic field up to1.1T and perpendicular to the incoming neutronswas applied on the samples.Beside this component we have to take into accountscattering contributions from free surfactantmaterial and from larger particles (aggregates). Thedata analysis showed that these types of particleswith log-normal distribution are of spherical shape.A volume weighted average of the core radius of<R’>=6.73nm, a constant thickness of the shell ofdR=2.61nm and volume fraction of magnetiteparticle=0.25% was determined for the core-shellparticles. The resulting scattering length density(Fig. 1) for the shell is found to be independent onthe H/D composition of the solvent, which indicatesthat the organic surfactant is nearly impenetrablefor the solvent. The nonmagnetic free surfactant hasa volume fraction of 0.7 vol% and a volumeweighted average of a radius of 2.62nm. Since thescattering intensity for the large particles dependson the polarisation state, they must also containmagnetic material. However, the ratio -/+ wasfound much smaller than expected for puremagnetite. It corresponds to a magnetite content ofonly 22%. These result suggests that the large

particles consist of a loose arrangement ofmagnetite mixed with surfactant molecules forminglarger aggregates. The volume weighted averageradius amounts to 17.8nm, which is 2.5 times largerthan the radius of the small magnetite cores.

0 2 4 6 8 10 12 140

2

4

6

8

10

_Core Shell Solvent

0.50

0.70

0.90

xD2O

scatt

erin

g leg

th d

ensit

y [1

010

cm-2]

Radius [nm]

Fig. 1: Scattering length density profile for core -shell particles.

0 5 10 15 20 25 30 35 40 45 500.00

0.02

0.04

0.06

0.08

0.10

0 5 10 15 20 25 30 35 40 45 500.0

0.2

0.4

N(R)

*V(R

) [a.u

.]

Radius [nm]

N(R)

*V(R

) [a.u

.]

Radius [nm]

Fig. 2: Volume weighted size distributions for thecase of the H0.2D1.8O solvent for core-shell particles(dotted), aggregates (dashed) and surfactant (shortdashed).

The data analysis for higher concentrations is inprogress.

[1] M. Kammel, A. Hoell, A. Wiedenmann,Scripta Materialia 44 (2001) 2341-2345.

[2] P. Görnert, N. Buske, Proc. 5th

INTERTECH Conference, Berlin, 2000.

198


EXPERIMENTAL REPORT Proposal N° MAT-04-637; EF-SF 3-05Instrument V4SANS investigations of Bariumhexaferrit

Ferro fluids and its precursors Local Contact A. Hoell

Principal Proposer: Armin Hoell, HMI - Berlin Date(s) of ExperimentExperimental Team: Armin Hoell, HMI - Berlin

Albrecht Wiedenmann, HMI - BerlinRobert Müller, IPHT – Jena (2nd date)

20.3. – 22.3. 2001 &02.8. – 05.8.2001

Date of Report: 18. 01. 2002The preparation of very fine magnetic particles hasattracted much interest in current Ferro fluid rese-arch due to the possibility of realizing newproperties. Some examples of common preparationmethods are the co-precipitation, the sol-gel tech-nique and the glass crystallization [1]. Especially,the latter has been proved to yield a magnetic Ba-hexaferrite nano sized powder (BaFe12-2xTixCoxO19with x=0.8) from those a new type of magneticliquid has been developed. Ba-Ferrite FFs were prepared by use of oleic acid,CH3(CH2)7CH=CH(CH2)7COOH, as surfactant anddodecane, C12H26, as carrier liquid. From thisconcentrated fluid three different diluted fluids inmixtures of protonated and deuterated dodecane,denoted by H (100% H containing dodecane), HD(ratio: 0.64 H / 0.36 D) and DD (0.33 H / 0.67 D),with a particle content between 1 and 4 vol % wereprepared for the SANS investigations. According toanalyse the complete structure of the FF’s (magne-tic core, surfactant layer, magnetic nano structure,aggregates and free surfactants) SANS measu-rements were performed with the instrument V4using the polarization option [2] and an horizontalmagnetic field up to 1.1 T applied to the samplesand directed perpendicular to the neutron beam. It was found that the FFs contain compositeparticles with barium hexaferrite cores of 4.1 nmradiuses with an impenetrable surfactant shell of1.8 nm thicknesses. Aggregates of 9.8 nm radiuseswere found which contain 1/3 of the magnetisationin addition to free surfactant molecules of 0.8 nmradiuses [3].

0 10 20 300.0

2.0

4.0

6.0

8.0

N(R

)*4 R

3 / 3

[10-3

nm

-1]

radius [nm]Fig.1: The volume weighted size distributions of thecore-shell particles (--), the aggregates (--) and freesurfactant molecules (--) in Ba-Ferrite Ferro fluids.

A glass cystallization series will be analysed accor-ding to clarify the kinetics of the Bahefe growth,fig.2. The intermediate stages (fig.3) of the Ferrofluid preparation will give results on the unwantedagglomerate formation and the magnetic structureand stability conditions of the particles.

0.01 0.1 1 100.01

0.1

1

10

100

1000 I-(Q); as quenched I+(Q); -"- I-(Q); 580°C 4h I+(Q); -"- I-(Q); 580°C 120h I+(Q); -"-

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig.2: The SANSPOL scattering curves of both polari-zation states of the Bahefe containing glass ceramics atdifferent annealing states are shown.

0.01 0.1 10.1

1

10

100

1000

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig.3: The nuclear scatterings of different FFprecursor states are shown: Bahefe-particles in solutedmatrix, dryed particles, particles partially coated inoleate with KOH, oleic acid coated in HNO3, waterand acetone washed, final Ferro fluid.References:[1] R. Müller et al, Proceed. ELECTROCERAMICS

IV, 5.-7.9.1994, Aachen, Vol. II, p. 1183.[2] A. Wiedenmann, Mat. Science Forum, 312-314

(1999) 315-324. [3] A. Hoell, R. Müller, A. Wiedenmann, W. Gawalek,

JMMM (2002) in print.

199

// brandt // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EF SF3-5Instrument V4Concentration effect in Co-Ferrofluids:

Field induced correlations Local Contact A. Wiedenmann*

Principal Proposer: Albrecht Wiedenmann, HMI Date(s) of ExperimentExperimental Team: Albrecht Wiedenmann, HMI

Armin Hoell, HMIMartin Kammel, HMI

Nov. 200019.03. - 22.03.01

Date of Report: *Size distributions, composition and magneticmoment of the composite particles have beendetermined previously on very diluted samples ofCo-Ferrofluids [1]. The set-up of inter-particlecorrelation under the influence of magnetic fieldwas studied in a second series of Ferrofluids withhigher Co-concentrations of about 1 vol.% (D1)and 5 vol. % (D5). SANSPOL measurements [1,2]have been performed at the instrument V4 in ahorizontal magnetic field of strength up to 1.1 Tapplied perpendicular to the incoming neutrons. The azimutally averaged intensities for unpolarisedneutrons <I(Q)>, plotted in Fig. 1, illustrate howthe scattering behaviour changes as a function ofCo-concentration and magnetic field. For randomorientation <I(Q)H=0>= [FN2 +2/3FM2]S(Q) isexpected at H=0 while for full alignment in strongmagnetic fields <I(Q)> is given by <I(Q)Hmax>=[FN2 +1/2FM2]S(Q). For the sample D1 thescattering observed at zero field scales fully withthat at H=1 T, i.e. there is no change of the particlearrangement in the external field. In sample D5 apronounced peak occurs at Q1=0.32 nm-1 when themagnetic field is turned on. This is fully confirmedby the SANSOPL results shown in Fig. 2. Inaddition to the high Q features characteristic for thecore-shell profile for both polarisation states a sharppeak occurs at Q1=0.32 nm-1 in the concentratedcase D5 only. i.e. the magnetic-nuclear cross termis clearly peaked resulting from the structure factorS(Q). Taking into account an additionalnonmagnetic scattering contribution (resulting froma small amount (1-5%) of spherical particles ofexcess surfactant molecules with R1.8), all curvesI(QH) , FM2 and FN2 could be adjustedsimultaneously by the same core-shell model asdescribed in [3]. In the concentrated sample D5 theset-up of strong correlations between the Co-particles in an external magnetic field are clearlyreflected by a structure factor S(Q). All curves arewell described using the same S(Q) for which weused the hard sphere model of Percus-Yevick. Theresulting S(Q) plotted in Fig.2 corresponds tovolume fraction =0.3 of hard spheres with a radiusRhc=8.65nm. Rhc is by a factor of about 1.5 largerthan the total radius R'+dR of the particles.Comparing the intensities parallel and

perpendicular to H did not show evidence for ananisotropic structure factor This implies a ratherdense packing of the particles under the influenceof the magnetic field rather than formation ofchains with the moment and chain directions alongthe magnetic field as predicted for dipoleinteractions.

Fig.1: Radial averaged SANS intensity of 1-vol% (triangles) and 5-vol% (circles) Co-Ferrofluids in C7D8 atH=0 (full symbols) and H=1.1T (open symbols).

Fig.2: SANSPOL intensities I+(QH) (solid triangles )and I-(QH) (open triangles) of 5vol% Co-Ferrofluids inC7D8 and magnetic (squares) and nuclear (circles)contributions from non-polarised neutrons. The solid linerepresents the common structure factor S(Q) used in themodel fits.[1] A. Wiedenmann, J. Appl. Cryst. 33(2000 )428- 432. and Physica B297(2001)226-233.[4] A. Wiedenmann, Magnetohydrodynamics37,3(2001)236-242[3] A. Wiedenmann, A. Hoell and M. Kammel in print JMMM (2002)

1E-1 11E-1

1

1E1

1E2

D1% H=0 D1% H=1T D5% H=0 D5% H=1T

Momentum transfer [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

0.1 10.1

1

10

100 I(+) I(-)

FM2

FN2

S(Q)


Scat

terin

g cr

oss-

sect

ion

[cm

-1]

200


EXPERIMENTAL REPORT Proposal N° EF: SF3-5Instrument V4Concentrated Ferrofluids and Polystyrene

fixed Magnetite studied by SANSPOL Local Contact A. Hoell

Principal Proposer: Armin Hoell, HMI – Berlin Date(s) of ExperimentExperimental Team: Armin Hoell, HMI – Berlin

Albrecht Wiedenmann, HMI - Berlin 19.3. - 21.3.2001 &30.7. - 02.8. 2001


We study the nano-structure of different Ferro-fluids in the frame of the priority program“SPP1104” of the German Science Foundation(DFG) named “Colloidal Magnetic Fluids: Basics,Development and Application of New Ferrofluids“in cooperation with other participating groups. Theaim of this report is to summarize the state of twoof our cooperations.

Technical Ferrofluids produced by Ferrotec(APG S10n and EMG905) will be studied incooperation with Dr. Odenbach (Uni. Bremen).These are high concentrated liquids containingmagnetite cores (about 7.2 vol% of magnetite coresD ~ 10 nm). Both have high saturation magneti-zations of 40 mT and differ in the viscosity values.Such high concentrated Ferrofluids show fieldinduced changes of the viscosity under shear stress.Theoretical studies on the rheological character-ristics of magnetic fluids yielded the existence offield- and shear stress dependent chainlikeaggregates [1]. Therefore, our structure estimationsby SANSPOL [2] (V4, HMI) will be the basics ofthe proposed rheological experiments during SANSinvestigations of Dr. Odenbach (Fig.1).

0.01 0.1 1 100.01

0.1

1

10

100

1000APG-S10n

I-(Q) I+(Q) INUC(Q) IMAG(Q)

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig.1: The SANSPOL curves the nuclear and themagnetic scattering curves of two ferrofluids,which can be used in rheological investigations ofDr. Odenbach.

The determination of the structural parts and thesize distributions in such concentrated many phasematerials is complex and under progress.

In most cases the composite magnetic core-shellparticles in a ferrofluid are stable againstcoagulation and sedimentation under limited phvalues and surfactant content of the carrier liquid.By means of micro-emulsion polymerisation thecomposite particles can be encapsulated into hydro-phobic polystyrene. With this technique dense andhomogeneous polystyrene shells are obtained pro-tecting the magnetic cores against corrosion andchemical reactions in general. Monoclonalantibody-coupling on the polystyrene surface willcreate the desired tissue selectivity useable formedical applications (tissue selective cancertherapy by hyperthermia).

0.01 0.1 110-2

10-1

100

101

102

103

104

105

Inuc

; PS-H,H:D=74:26 I

nuc; PS-H,H:D=4:6

Inuc

; PS-H,D2O

Inuc

; PS-H,H2O

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

Fig.2: SANS curves (only nuclear scattering parts) ofpolystyrene encapsulated magnetite particles witholeic acid shells.

In cooperation with Dr. Landfester (MPIKG-Golm)first sample sets of polystyrene encapsulated mag-netite particles are under SANSPOL investigations.It is known from TEM that most of the polystyrenecapsules contain many separated magnetite crystals.One set was prepared using normal polystyrene andthe other using deuterated one. Additionally, theH/D ratio of the carrier liquids (water) was varied.The qualitative behaviour of the nuclear scattering(fig. 2) follows the expected H/D ratio determinedcarrier liquid contrasts. [1] A. Yu. Zubarev, L. Yu. Iskakova, JETP 80

(1995) 857 – 866.[2] A. Wiedenmann, Mat. Science Forum, 312-

314 (1999) 315-324.

0.01 0.1 1 100.01

0.1

1

10

100

1000EMG905

I-(Q) I+(Q) INUC(Q) IMAG(Q)

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

0.01 0.1 110-2

10-1

100

101

102

103

104

105

Inuc; PS-D,H2O I

nuc; PS-D,D

2O

Inuc

; PS-D,H:D=5:5 Inuc; PS-D,H:D=8:92

Q [nm-1]

Scat

terin

g cr

oss-

sect

ion

[cm

-1]

201

// brandt // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EF-SF3-5Instrument V4Field induced ordering in FerrofluidesLocal Contact A. Wiedenmann*

Principal Proposer: Albrecht Wiedenmann, HMI Date(s) of Experiment

Experimental Team: André Heinemann, HMI Armin Hoell, HMIMartin Kammel, HMI Albrecht Wiedenmann

1.- 4.8.200115.-21.10.2001

Date of Report: *

Dipole interaction between magnetic moments ofmono-domain nanoparticles in Ferrofluids (FF)should favour the formation of chains with themoment and chain directions along the magneticfield. Such chain arrangements should give rise tostronger inter-particle correlation along H i.e. to ananisotropic structure factor S(Q). In previousmeasurements on 2.5% Co-FF we observed theonset on some kind of ordering induced by anexternal magnetic field, described by structurefactor S(Q). However, an isotrope Percus-Yevictype S(Q) was found [1] reflecting a rather densepacking of the core-shell particles in theconcentrated systems which is induced by anexternal magnetic field. In Magnetite-[2] and Ba-Hexaferrite based FF [3] the presence of largeaggregates up to now prevented the determinationof S(Q) resulting from inter-particle interactions.

A new series of samples have been specificallyprepared in cooperation with Berlin heart AG forinvestigations of the spontaneous or field inducedparticle interactions. A systematic variation of thefollowing structural parameters were intended :

Size of cores via preparation conditions, Magnetic particle moment depending on

material (Co, Fe3O4 , Ba-hexafferit), Average particle distance via concentration

(1-10 vol%), Minimum particle distance depending on

shell size (single shell, double shell).

The aim of this investigations is to study the onsetand evolution of S(Q) as a function of theseparameters, possible effects of magnitude anddirection of the applied magnetic field (H// orperpendicular) and the influence of Brownianrelaxation by freezing of the carrier liquid.

SANSPOL and conventional SANS measurementshave been started using different experimental set-up:

Horizontal electromagnet, 0 < H < 1.1T,

T=300K Vertical cryomagnet, 0 < H <3 T, Field

perpendicular to incident neutronsT=300.

Vertical cryomagnet, 0 < H < 3T, Fieldperpendicular to incident neutrons.Temperature variation 100 <T< 300K.Freezing of solvent by zero-field- coolingand field-cooling.

Horizontal cryomagnet HM1, field parallelto incident neutrons, used for the first timewith SANSPOL: (Limitation of Hmax at0.3 T due to interference with spin-flipper)

0 < H < 0.3T 0 < H < 4 T , conventional SANS,

Temperature variation 150 < T < 300 K.

The data reduction is in progress. For the analysiswe have to use the procedure of simultaneousmodel fitting of I+(Q), I-(Q) , Inuc(Q), and Imag(Q) .This is actually performed by adapting the softwarepackage of R. Heenan , ISIS [4]

[1]A. Wiedenmann, A. Hoell, M. Kammel, ,JMMM (2002) in press

[2]M. Kammel, A. Hoell, A. Wiedenmann,Scripta Materialia 44 (2001) 2341-2345

. JMMM (2002) in press[3]A. Hoell, A. Wiedenmann, R. Müller

JMMM (2002) in press[4] R.Heenan: "FiISH" reference manual

RAL report 89-129

202

ef_27 // Uwe Keiderling // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EF-NanomatInstrument V4Time-resolved in-situ SANS investigation of the sintering behavior

of nanocrystalline Y2O3-doped ZrO2 ceramicsLocal Contact U.Keiderling

Principal Proposer: H.Hahn, M.Winterer (TU Darmstadt), Date(s) of ExperimentU.Keiderling (TU Darms.), A.Wiedenmann (HMI)

Experimental Team: U.Keiderling, J.Seydel (TU Darmstadt) 14.5.-20.05.200116.7.-21.7.2001


The sintering behavior of zirconia ceramics dopedwith 0, 4, 10, and 12 mol-% yttria was investigatedwith in-situ SANS. The nanocrystalline powder wasproduced by Chemical Vapor Synthesis (CVS) andpressed into greenbodies. The greenbodies weresintered in a vacuum furnace at temperaturesbetween 300°C and 1200°C. Time-resolved SANSspectra were measured during the vacuum sinteringprocess in-situ, covering a wide range of thescattering vector Q between 0.05 nm-1 and 2 nm-1. The measurements were performed using the"HTF-1" in-situ furnace of BENSC, in atemperature range between 300°C and 1200°C. Theexperimental set-up included a neutron wavelengthof 0.605 nm with a wavelength distribution(FWHM) of 10%, and three different sample-detector distances of 1.092 m, 4.000 m and15.982 m, covering a total Q-range between0.05 nm-1 and 2 nm-1. The data reduction wasperformed using the HMI-standard "BerSANS"software package. The two-dimensional datarevealed a perfect circular symmetry, and wereradially averaged.Before starting the temperature-time program foreach sample-detector distance, a referencemeasurement of the greenbody mounted into thecold furnace was done at room temperature. Afterthis measurement, the furnace was heated to 300°Cin a single step, with a heating rate limited toapproximately 5 K/min in order to avoid stressesand cracks in the sample. The followingtemperature-time sintering program spanned atemperature range from 300°C to 1200°C, withincremental steps between two measurements of50°C. The heating from one measurementtemperature to the next one was again performedwith a heating rate of 5 K/min. After reaching eachmeasurement temperature, a pause of 5 min wasapplied for the sample to equilibrate, followed bythree measurements of 5 min each which wererecorded into separate data files, in order toestimate the speed of the structure evolution duringthese first 15 min after reaching a new temperature.At the end temperature of 1200°C, a final 3 hoursmeasurement of the long-time sintering behavior ofthe sample at this fixed temperature was recorded.

Fig.1 shows the average particle sizes calculated byinverse Fourier transformation from theexperimental scattering curves for selectedtemperatures. It can be concluded from the figurethat a slight particle growth already starts at verylow temperatures, but only significantly acceleratesat temperatures around 1000°C. However, theincrease of the relative density of the samples (i.e.the disappearing of pores) already occurs at a lowertemperature.

Fig.1: Average particle size RAvg, and relativedensity /0 determined by dilatometer experiment.

203

ef_28 // Uwe Keiderling // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° EF-NanomatInstrument V4SANS investigation of the dynamic sintering behavior of

nanocrystalline Y2O3-doped ZrO2 ceramics with high timeresolution Local Contact

U.Keiderling

Principal Proposer: H.Hahn, M.Winterer (TU Darmstadt), Date(s) of ExperimentU.Keiderling (TU Darms.), A.Wiedenmann (HMI)

Experimental Team: U.Keiderling, J.Seydel (TU Darmstadt) 12.11.-14.11.2001


The dynamic sintering behavior of nanocrystallinezirconia ceramics doped with 12 mol-% yttria wasinvestigated with small angle neutron scattering(SANS). The nanocrystalline powder was producedby Chemical Vapor Synthesis (CVS) and pressedinto greenbodies. The samples were heated in thein-situ furnace HTF-1 from room temperature to1000°C or 1200°C, respectively, with a heating rateof more than 200 K/min, reaching the finaltemperature within a very short time ofapproximately 4 minutes. At this final temperature,the samples were sintered for a total time of 3hours. SANS spectra were measured during thissintering process with a time resolution of only 2minutes, yielding approximately 90 snapshots ofthe structure evolution during sintering. Themeasurements covered a wide range of thescattering vector Q between 0.035 nm-1 and 3 nm-1.This was achieved by using a new samplegreenbody (all from the same powder batch) foreach sample-detector distance of 1.1 m, 4 m, and15.8 m, respectively. The calculation of the size distributions of grainsand pores from the corrected scattering curves as afunction of sintering time is currently underprogress, using a direct model fitting with sets oflognormal size distributions. However, due to thevery short measurement time of only 2 minutes persnapshot, there is an inherent lack of statistical dataquality. This leads to inconsistent results for theevolution of grain and pore sizes of a sample withtime, if the standard processing technique normallyused for data with good statistics is being applied tothese data schematically. Therefore, a special dataprocessing techniqueis required in order tocompensate this effect, allowing a full preservationof the high experimental time resolution in the finalresults. The fine-tuning of this technique iscurrently under progess.These measurements, holding the samples at aconstant temperature for the entire time of 3 hours,are only the first part of a more complex time-resolved in-situ project. Upcoming measurementswill apply different time-temperature profiles, likeheating the samples to a higher temperature (e.g.1300°C), for a short moment, then cooling them

down again and holding them at a lowertemperature for the remaining time. The goal ofthese investigations is to determine if theapplication of a non-constant time-temperatureprofile can optimize the sintering process ofnanocrystalline structures, yielding sinteredmaterials which reveal both a high relative density(supported by a higher sintering temperature), and agrain size which is not too large (supported by alower sintering temperature).

204


EXPERIMENTAL REPORT Proposal N° MAT-04-641Instrument V4Pore Microstructure in Ceramic Thermal Barrier

Coatings Local Contact P. Strunz

Principal Proposer: G. Schumacher, BAM Berlin Date(s) of ExperimentExperimental Team: P. Strunz, HMI Berlin

R. Vassen, FZ Jülich 14. - 16.08.2001


Ceramic thermal barrier coatings (TBC) allowsfor an increase of temperature in thecombustion chamber of turbines by more than100ºC. The aim of the present SANSexperiment was to study the microstructure ofpores in heat-treated TBC deposited byplasma-spraying on Ni-base superalloys.Plasma sprayed deposits contain a largenumber of cracks and pores which determinetheir properties. The application of SANS iscomplementary to standard techniques and isintended for a bulk characterization of thewhole (not only the open) porosity.

Altogether three sets of samples wereinvestigated differing by spray parameters andthus also by their porosity. The samples weresintered at 1200ºC at air for different times: 0,1, 10 and 100 hours. The scattering curvestogether with the fitted ones for the first set ofsamples (denoted 47) are displayed in thefigure.

The parameters, refined using a sizedistribution of spheres as a model, are writtenin the table for this set of samples. Threepopulations of pores were necessary todescribe the data: large, medium-size andsmall pores.

All samples contain large pores and cracks (>90 nm) which produce the main contribution tothe scattering intensity. Interpretation ofchanges of morphology for these large pores

and cracks is difficult because of accessible Q-range and due to the multiple scattering. Moredetails about the size and volume of this partof the size distribution of pores can beextracted using complementary DC SANS.

The volume fraction of the medium-sizepopulation of pores decreases with thesintering time. The decrease during the firsthour of sintering is the most significant. At thisearly stage, the mean size of these poresincreases.

The mean size of small pores continuouslyincreases while their volume fractiondecreases with the sintering time. However,the scattering is most probably influenced bythe incoherent scattering from hydrogen for theas-sprayed sample. Therefore, the volumefraction and size can not be determinedprecisely for this sample (see the questionmark in the table).

It comes out from the results that importantchanges appear during the whole sinteringperiod. But the most visible (for the pin-holeSANS) are those which happen at the earlystages of sintering. Therefore, the proposersintend to measure the early stage in moredetail either in situ or with samples preparedon a finer time scale. Particularly, we expect todistinguish between scattering fromsubnanometric inhomogeneities andincoherent scattering from hydrogen in thisway.

Sample

t(h)

R1(nm)

c1 (-)

R2(nm)

c2 (-)

47_A 0 ? 0.6 ? 6 16 5.5347_B 1 2.62 3.43 42.4 2.6647_C 10 3.51 2.07 40.3 2.3347_D 100 6.34 1.61 41.1 2.09

t ... sintering time; R1,2, c1,2 mean radius and relativevolume fraction of small, resp. medium-size pores.

1E-3 0,01 0,1 1 101E-3

0,01

0,1

1

10

100

1000

10000

100000

1000000

Set 47 47_A

(sintering time 0 h) 47_B

(sintering time 1 h) 47_C

(sintering time 10 h) 47_D

(sintering time 100 h)d/d

(cm

-1sr

-1)

Q (nm-1)

205

cnr


EXPERIMENTAL REPORT Proposal N° MAT-04-0645Instrument V4Investigation of Cavities in superplastically

deformed Y-TZP by SANS Local Contact P. Strunz

Principal Proposer: Jan Šaroun, Nuclear Physics Institute, Řež Date(s) of ExperimentExperimental Team: P. Strunz, HMI Berlin

V. Ryukhtin, NPI, ŘežS. Harjo, Y. Motohashi, Ibaraki University

10.7.2001 – 11.7.2001


Void microstructure in superplastic ceramics is asignificant indicator of the physical mechanism ofsuperplastic deformation. It has been studied byconventional porosimetric techniques in variousstages and conditions of deformation process. Ourrecent ultra small angle neutron scattering(USANS) experiments enabled to measurealternatively the bulk porosity with the resultsconsistent to those of other techniques (SEM,Archimedes) as for the volume fractions. Thesemeasurements also indicated the presence of voidanisotropy, which is however difficult to measure atdouble-crystal USANS instruments. Theexperiment at HMI has therefore been carried out tomeasure the mean aspect ratio of voids independence on applied strain. The specimens of3mol% yttrium stabilised tetragonal ZrO2polycrystal (3Y-TZP) were pre-deformed from=0% to 200% at a constant strain rate of‘=3.3 10-4 s-1 at T=1723 K. They were measuredwith the strain axis vertical for detector distance LDof 4 and 16 m and neutron wavelength 0.6 nm. Thedata were evaluated by fitting an incoherent sizedistribution of rotation ellipsoids with the axisparallel to the applied deformation. The modelparameters were fitted directly to the 2-dimensionaldata by indirect FT method. The only relevantparameters were the aspect ratio and specificsurface of the ellipsoids, since we could see onlythe Porod region of the scattering function. Thesimultaneous evaluation of the HMI data with theUSANS results is under way and should provideconsistent characteristics of pore surface,anisotropy and size distribution. The results inFig.1 show the development of the anisotropy andspecific surface during deformation. Thedifferences between the two curves indicate theaccuracy of the measurement and data evaluation.The results agree qualitatively with earlierobservations by SEM and confirm that the processis dominated by grain deformation at < 10%,while other mechanisms (cavitation and grainboundary sliding) prevail at larger strains [1].The simple microstructural model was sufficient todescribe scattering from the samples deformed atlow rate. However, the scattering pattern becomes

more complicated at high strain rate, where anelongation parallel to the deformation axis appearsin addition to the slightly horizontally stretchedpattern typical for low rates (Fig.2). Thisphenomenon has never been observed before and isprobably connected with creation of flatdeformation cracks or with preferred ordering ofvoids revealed by recent USANS experiments.

References:[1] Y. Motohashi , N. Sugeno , S. Koyama and TaketoSakuma, Mater. Sci. Forum 243-245 (1997), 399 -404

-0.05 0.00 0.05

-0.05

0.00

0.05

Qx, Å -1

Qy,

Å -1

-0.05 0.00 0.05

Qx, Å -1

' =0.33 10-4 s-' =66 10-4 s-1

Fig. 2. SANS intensity pattern for samples deformedto =100% at low and high deformation rates.

Fig. 1. Evolution of void aspect ratio and specificsurface with increasing strain.

0 50 100 150 200

1.0

1.1

1.2

1.3

0 50 100 150 2000

5

10

15

20 Ldet = 16 m Ldet = 4 m

3Y-TZP

Mea

n as

pect

ratio

[%]

3Y-TZP

Ldet = 16 m Ldet = 4 m

spec

ific

surfa

ce [1

03 cm

-1]

[%]

206


EXPERIMENTAL REPORT Proposal N° EFInstrument E9Effect of high-pressure hydrogen

charging on austenitic stainless steels Local Contact

Principal Proposer: S. Danilkin, HMI Date(s) of ExperimentExperimental Team: S. Danilkin, HMI

M. Hoelzel, TU DarmstadtD. Toebbens, HMI

10.10.01 – 15.10.01


The mechanisms of hydrogen-induced phasetransformations in austenitic stainless steels are stillunder debate. In particular, the role of stresses hasto be considered. So far, only a few studies onsteels exhibiting a uniform distribution of hydrogenhave been published, showing controversial results[1, 2].The task of our experiment was to clarify theexistence of hydrogen-induced phasetransformations in steels homogenous hydrogenatedat high pressures of several GPa.We performed neutron diffraction studies on Fe-25Cr-20Ni samples hydrogenated in a high pressurecell at p = 2.3 and 7.0 GPa and T = 350°C. Afterhydrogen loading, the samples were quenched toliquid nitrogen temperature and kept at it until theexperiment was done to prevent the outgassing ofhydrogen.The diffraction data were collected at 80 K withdiffractometer E9 using neutrons with = 0.1307nm (determined by a Y2O3 standard). During themeasurements, the cryostat was rotated to diminishtexture effects. Prior to the investigations ofhydrogenated steels, an uncharged sample (in initialstate) was measured. The data were analysed byRietveld refinement using the Fullprof software. The investigations revealed that all samples consistonly of a single fcc phase. An increasing hydrogencontent leads to a continuous increase of the latticeparameter without the occurrence of phasetransformations (the additional reflections in Fig. 2result from aluminium covering this sample). The data analysis revealed that in both sampleshydrogen occupies only the octahedral interstitialsites. In case of the sample charged at 2.3 GPa, thehydrogen occupancy was refined to be about 43%,whereas an occupancy of 92% was determined forthe sample charged at 7.0 GPa. Thus, our data do not show phase transformationsin Fe-25Cr-20Ni charged in hydrogen gasatmosphere, whereas they were reported to occur incathodic charged steels, exhibiting high hydrogengradients.

Fig. 1: Neutron diffraction pattern of Fe-25Cr-20Nisteel charged with hydrogen at 2.3 Gpa

Fig. 2: Neutron diffraction pattern of Fe-25Cr-20Nisteel charged with hydrogen at 7.0 GPa

Tab. 1: summary of the results

sample cellparameter

hydrogenoccupancy

Bragg-R-factor

initial state 3.5818(1) - 5.6

2.3 GPa H2 3.6564(2) 0.43(4) 3.9

7.0 GPa H2 3.7771 3) 0.92(6) 2.8

References:[1] N. Narita, C.J. Altstetter, H.K. Birnbaum, Met.Trans. 13A (1982) 1355[2] V.N. Bugaev, V.G. Gavriljuk, Y.N. Petrenko,A.V. Tarasenko, Int. J. Hydrogen Energy 22 (1997)213

207

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EXPERIMENTAL REPORT Proposal N° MAT-04-584Instrument V4Evaluation of Irradiation Embrittlement of

Reactor Pressure Vessels (RPV) Local ContactP. Strunz

Principal Proposer: Andreas Ulbricht, FZ Rossendorf e.V. Date(s) of ExperimentExperimental Team:

Andreas Ulbricht, FZ Rossendorf e.V.Pavel Strunz, HMI Berlin

18.-21.06.2001


0.001

0.01

0.1

1

10

10.001

0.01

0.1

1

10c)

b)

a)

irradiation0.133 dpa0.078 dpa0.010 dpaunirradiated

dΣ/d

Ω (Q

, α=π

/2)

/ cm

-1sr

-1dΣ

/dΩ

(Q, α

=0)

/ cm

-1sr

-1

320.50.30.2Q / nm-1

dΣ/d

Ω (Q

) mag

/ c

m-1sr

-1

Fig. 1: SANS cross sections of different statesof the steel A533B a) measured total (coherent+ incoherent), mag. + nucl. SANS b) separatedcoherent nucl. and c) coherent mag. scatteringcontribution.

[1] J. Böhmert, H.-W. Viehrig, A. Ulbricht, J.Nucl. Mater. 297 (2001) 251-261.

benscrep-MAT-04-584.doc // Andreas Ulbricht // 30.01.02 Seite 1 von 1


The A533B Cl.1-type RPV steel, designatedJRQ, has been used as IAEA reference steeland shows a high sensitivity against radiationembrittlement. Specimens from this materialwere irradiated to three different levels of neu-tron fluences. Thus, the investigation allows torealize the dependence of microstructuralchanges on the fluence and a comparison withresults on VVER-type RPV steels [1], whichdiffer from the Western RPV steel design.

The measurements were carried out withsamples of 0.8 mm thickness under a satu-rating magnetic field perpendicular to the neu-tron beam (λ = 0.6 nm) direction.

The total scattering intensity measured per-pendicular to the direction of magnetization isdepicted in Fig.1a for the unirradiated and thethree irradiated samples. The results after sub-traction of the incoherent scattering contri-bution (mainly caused by Fe isotopes) andseparation in coherent nuclear and magneticscattering are showing in Fig.1b and 1c.

Irradiation enhances the coherent scatteringintensity for Q > about 0.4 nm-1 in every case.

Both magnetic and nuclear SANS crosssection yields to similar size distributionfunction. The irradiated conditions have asharp peak between 0 < R < 3 nm with themaximum near 1 nm. The mean radius of theirradiation induced defects increase slightlyfrom 0.95 to 1.05 nm.

The volume content of defects increaserapidly for dpa < 0.01 and than approximatelylinear with the irradiation. This behaviour isalso recognizable in the change of themechanical properties.

The A-ratio (coherent SANS perpendicularand parallel to the magnetization) variesbetween 2.2 and 3.1 in the Q-range from 0.2 to3 nm-1 for all material conditions. In the rangebetween 0.8 and and 3 nm-1, in which theparticles of about 1 nm radius specially scatter,the A-ratio is nearly constant and amounts to2.2 - 2.4.

The evolution of nanoscaled microstructuraldefects with a mean radius of about 1 nm due

to neutron irradiation is proven for other type ofRPV steels and in other investigations andseems to be a characteristic feature for theinteraction between neutrons and atoms inRPV steels independent of composition andinitial microstructure.

0.001

0.01

0.1

1

10

208


Name(s) Affiliation

Proposal Nº

Instrument

Local Contact


Date of Report

Principal Proposer:

Experimental Team:

A SANS study of Corax N330 V4

E. Hoinkis HMI

E. Hoinkis 4. 7. 2001

5. 2. 2002

Corax N330 is a pelletized carbon blackwhich is commercially produced by Degussa-Hüls (Frankfurt). It is used as a filler in polymersand consists of primary particles which formgrape like aggregates. The surface properties ofthe primary particles are important for thevulcanization. The higher the surface roughness,the better are the dynamical properties of thepolymer. A measure of the surface roughness isthe surface fractal dimension, 2 Ds 3, whereDs = 2 indicates a smooth surface. Surfacefractals show I(q) ~ q-, where = 6-Ds. In [1]Ds = 2.28 was determined by use of SAXS.However, Ruland [2] proposed the deviationfrom Porods law ( = 4 ) to be very probably dueto 1D density fluctuations within the carbonparticles, but not to a fractally rough surface. Here we check wether inaccessible microporesand graphene layers contribute significantly tothe measured intensity I(q). A comparison of theN2 adsorption isotherm data of a standardgraphitized carbon black and Corax revealed theabsence of accessible micropores. The Figureshows I(q) for Corax N330 before (dots) andafter (triangles) suspension in d-cyclohexane,which has about the same scattering lengthdensity as the carbon. = 3.95 0.01, in contrastto = 3.72 0.07 in [1]. The small deviationfrom Porods law found here suggest that thesurface of the primary particles is essentiallysmooth with respect to the interaction withneutrons. For q < 1 nm-1, I(q)susp.<< I(q)orig., butfor q >1nm-1, I(q)susp is of the same order ofmagnitude as I(q)orig, which is due to inaccessiblemicropores. I(q)dif = I(q)orig - I(q)susp shows aslope of about -2 for q > 2 nm-1, which ischaracteristic for 2D features, e.g. graphenesheets. For a quantitative description of I(q)dif thecorrelation length was determined from a Debye-Büche plot for q > 0.1 nm-1, and than a modelconsisting of a Debye term and a term forinfinitesimal thin cylinders was fitted to the datafor q > 0.5 nm1. The continuous line represents

the theoretical I(q).The dashed line represents thescattering from graphene sheets. The mean size ofthe primary particles calculated from thecorrelation length is 26 nm, in agreement withTEM images [3] and [4], and the size of thegraphene sheets is 1 nm. These sheets consist thenof about 12 benzene rings.

Fig. : The scattered intensity I(q) as function of q =(4/) sin . ( = 0.6 and 0.45 nm, 2 = angle)[1] T.P. Rieker, M. Hindermann-Bischoff, F. Ehrburger-Dolle, Langmuir 16 (2000) 5588[2] W. Ruland, Carbon 39 (2001) 323[3] T. Rieker, S. Misono, F. Ehrburger-Dolle, Langmuir 15(1999) 914[4] P. Schubert-Bischoff, private Comm. (2002)

209

EXPERIMENTAL REPORT

Investigations of metal foams

Proposal NÆ

MAT-02-271

Instrument E1

Local Contact

J. Klenke


3. 12. - 11. 12. 2000

Principal Proposer: John Banhart, Fraunhofer Institute IFAM

Experimental Team: Heiko Stanzick, Fraunhofer Institute IFAM

Jens Klenke, HMI

Sergej Danilkin, HMI


Introduction

Solid metallic foams have interesting properties such

as high stiness in conjunction with very low specic

weight, making them attractive, e.g., for automotive

and aerospace industries. In industrial production

of metal foams coalescence and drainage have to be

minimised in order to obtain a uniform pore structure

and good mechanical properties of the nal material.

Often an analogy is drawn between metal foams and

aqueous foams. Fig. 1 shows the calculated liquid

fraction prole of an initially uniform vertical column

of aqueous foam which turns into a non-uniform pro-

le in the so-called free-drainage process. One goal

of our work was to check whether a similar drainage

behaviour can be observed for metal foams. In this

experiments neutron radioscopy was used to measure

drainage eects in lead alloy foams [1].

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

time

TOPBOTTOM

- Liq

uid

fract

ion

vertical distance

Figure 1: Calculated liquid fraction proles of an

aqueous foam in a free-drainage experiment


Lead-tin foams (PbSn30) containing 1 vol.% B4C-

powder to enhance neutron absorption were pro-

duced following the powder compact foaming route.

Foams were generated in a pre-heated furnace by

melting the foamable precursor material. The fur-

nace which allows a horizontal lead foam column in

an Al tube to be produced, was equipped with two

water-cooled Al windows through which the neutron

beam (10 mm high, monochromatised to 0.24 nm)

could pass. The sample temperature was recorded

throughout the experiment. After foaming had been

completed the column was tilted into the vertical po-

sition thus initiating gravitationally induced ow to-

wards the lower end of the column. In this position

the column was periodically swept through the neu-

tron beam at 1.6 cm/s with an amplitude of 17 cm

while the attenuation of neutrons going through the

7 mm thick lead foam layer was recorded as a func-

tion of time. The vertical spatial resolution of the

measurements is about 15 mm.

A representative example of this experiments is

shown in Fig. 2. In this case the transmitted inten-

sity T was normalised with the prole obtained from

the unfoamed precursor material Tp. As the experi-

ment was started 10 seconds after foaming had com-

pleted the temperature is almost constant through-

out the experiment. Drainage is clearly visible in

Fig. 2. There is a pronounced downward movement

of the liquid associated with a reduction of density for

the upper part of the sample. Correspondingly, the

liquid pool which builds up on the bottom is larger.

There is a qualitative agreement with the nal den-

sity prole predicted for liquid foams as shown in

Fig. 1, namely a linear behaviour over most of the

column height. Only the strong increase in density

near the bottom cannot be seen in Fig. 2 due to the

limited spatial resolution of the measurements.

0 20 40 60 80 100

-0.2

-0.1

0.0

0.1

0.2

0.3

BOTTOM TOP

10 s 329˚C 28 s 331˚C 191 s 349˚C 227 s 351˚C 245 s 353˚C 263 s 354˚C

ln(T

/Tp)

vertical distance [mm]

Figure 2: Tilting experiment of PbSn30 foam,

T = 360ÆC

A more detailed of the drainage process would

210

require a higher spatial and time resolution. Major

improvements can be expected from replacement of

the point by a line or even a 2D detector. Moreover,

higher absorptions would be advantageous. Use

of Cd as absorption enhancing alloying element in

replacement of B4C is highly desirable but requires

an air-tight furnace and appropriate safety measures.

[1] H. Stanzick, J. Banhart, J. Klenke, S. Danilkin,

Applied Physics A (ICNS 2001 Proceedings), ac-

cepted for publication.

211


EXPERIMENTAL REPORT Proposal N° *Instrument B7Redistribution of ion-implanted boron in the

photoresist S1813 Local Contact D.Fink

Principal Proposer: D.Fink, HMI Berlin Date(s) of ExperimentExperimental Team: M.Behar, UFRGS Porto Alegre, Brazil

M.F.Soarez, UFRGS Porto Alegre, BrazilM.Müller, HMI Berlin

1.1.2001-31.12.2001


B+ ions of 100 keV energy were implanted intothe photoresist S1813 up to fluences of 1014 cm-

2/cos(), for directions α (in reference to thesurface normal) of 7, 30, 45, and 600, andsubsequently thermally annealed at 100, 150, 200,and 250° C for 1 hour each. (The cosine factor inthe fluence is introduced to compensate thegeometrical reduction of the overall implantedboron concentration, so that one obtainscomparable boron concentration in all samples,independently of the implantation direction). Theboron depth distributions were measured withNeutron Depth Profiling („NDP“) at the Berlinresearch reactor BER II (position B7).

Fig.1: Boron depth distributions in S1813, as-implanted (RT) and after thermal annealing. Thetwo peaks stem from the boron redistribution atelectronic and nuclear defects, respectively.

It turned out that in no case, the theoreticallyexpected depth distributions were found. Instead,the profiles indicated considerable redistribution ofall implanted boron atoms already during theimplantation at room temperature. This contrasts toearlier examinations of B and Li in otherphotoresists (AZ111, AZ1350) where only a fractionin the order of 5 to 20 % of the implanted ionsredistributed, and where the majority of the ionsfollowed their theoretically predicted implantationprofiles („TRIM“ code). As subsequent ageing of thesamples for up to half a year left the boron depthprofiles unaffected, the initial redistribution processwas ascribed to radiation enhanced mobility. Thismobility is strongly influenced by trapping in defects

of both nuclear and electronic origin, Fig.1. Thiscontrast again to the implantation into the otherphotoresists, where only electronic defects acted astraps. Detectable thermal mobility is observed onlyafter annealing up at least 1000 C. In this case partof the defects released their trapped boron atomswhich subsequently underwent a hinderedmigration (i.e. affected by repeated trapping anddetrapping in surviving defects) in the ion-implantedregion, and a regular thermal diffusion in deeperregions (see the tails in Fig.1). This peculiar type ofthermal desorption spectrometry (TDS) enablesone to get some feeling for the trapping efficiencyand stability of both electronic and nuclear defects.It turns out that at ambient temperature, nucleardefects are about 10 times more efficient thanelectronic ones for trapping. At 100° C, part of theelectronic defects decay, followed by the collapseof the nuclear traps between 100 and 200° C, withsome remaining electronic defects being stableeven at 250° C (Fig.1). With a self-developed modified tomographicreconstruction (“MOTOR”) approach, the 3D shapeof the nuclear defect distribution, as marked by thetrapped B atoms, was reconstructed. It turned outthat it follows nicely the theoretical prediction evenin three dimensions, and even after thermalannealing, Fig.2.

Fig.2: The nuclear damage distribution in S1813photoresist in 3 dimensions, as reconstructed fromdepth distributions of an implanted boron markerthat was implanted into various directions.Electronic contributions subtracted.

212

ef_35 // Andreas Gorzel // 21.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° *Instrument E1Test measurements with a refillable

3He filter cell Local Contact J. Klenke*

Principal Proposer: A. Rupp, HMI, Berlin Date(s) of ExperimentExperimental Team: A. Rupp, HMI, Berlin

A. Gorzel, HMI, BerlinJ. Klenke, HMI, Berlin

08.11. – 13.11.2000


3He Neutron spin filters are pure transmissive andcan be used over a broad range of wavelengths (0.1Å to 16 Å). They promise to open newexperimental fields, in particular in the case ofdivergent beams as well as with white beams [1].Therefore, investigations to obtain practical filtercells and the construction of a filling station tosupply them is a focal point in the instrumentaldevelopment programme at HMI [2].

A neutron experiment to test a first HMI-maderefillable 3He filter cell under nearly real conditionshas been performed. The cylindrically shaped cellmade of quartz glass is 9 cm in length and 5 cm indiameter. To enable direct optical pumping bothfaces are optically flat. After a careful purificationprocedure by evacuating and baking the cell up to400°C for several days, it has been coated insidewith Cs to reduce wall relaxation significantly [3].Then it has been filled with spectroscopically pure3He to a pressure of about 3.6 mbar to allow directoptical pumping. The resulting 3He nuclearpolarisation of about 10% was sufficient to performNMR measurements to estimate the cells wallrelaxation rate. A total time constant of = 36 hoccurred, encouraging us to try a first neutronexperiment with that cell.

It has been filled with polarised 3He at theUniversity of Mainz at the filling station of thegroup of Prof. Heil. A filling pressure of 940 mbarhas been chosen, yielding a neutron transmission ofmore than 20% [4]. A special transportation unitserves to keep the filled cell in a magnetic guidefield during transportation as well as during use [5].

With the filter cell inside, it was placed at thesample position of E1. Adaptation of the verticalpolarised incoming neutron beam ( = 2.4 Å) to theaxially oriented 3He nuclear spins was achieved bymeans of an adiabatic spin rotator as well in frontof the cell as behind it. Neutron spin orientationcould be changed making use of a spin flipper. Atthe beginning the experiment was performed with aHeusler analyser which later on has been removed.

In the first case the decay of the 3He polarisationhas been determined from the decrease of the countrate for the preferentially detected spin state, in the

second case from the flipping ratio, considering thefinite flipping ratio of the flipper and the Heuslermonochromator in the incoming beam, as well. Theresult is shown in Fig. 1.

Fig.1: Filter cell filled in Mainz and tested at E1:decay of the 3He polarisation

Already in this first attempt a total relaxation timeconstant of = 50 h was observed. However, wallrelaxation also can even be smaller, because of astill uncertain contribution from slight magneticfield gradients inside the transportation unit. Futuretests with the aim to improve relaxation behaviourwill also elucidate this question. The transmissionof the windows was found to be 80%.

Acknowledgement

We are very grateful to Prof. Heil and his group at theUniversity of Mainz who enabled filling of our filter cell attheir filling station.

The work has supported in parts by the European Unionthrough the RTD-TMR programme „Cool NeutronOptimisation” and the RTD-IHP programme ENPI.

References

[1] H. Humblot et al., Neutron News 8(4) (1997), 27-32[2] A. Danzig et al., Physica B 276-278 (2000), 185-186[3] W. Heil et al., Phys. Lett. A 201 (1995), 337-343[4] R. Surkau et al., Nucl. Instr. and Meth. A 384 (1997), 444-450[5] A. Danzig, A. Rupp, Physica B 267-268 (1999), 344-347

0 10 20 30 40 50 600,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,50

Tran

spor

tatio

nan

dad

just

men

t

Exponential fitP0= 0,47 = 50 h

3 He

Pola

risat

ion

Elapsed time [h]

Transmissions of one spin state Measurement of the flipping ratio

213


EXPERIMENTAL REPORT Proposal N° EF-SF3-5Instrument V4The use of a refillable 3He filter cell in Small

Angle Neutron Scattering Local Contact A. Wiedenmann

Principal Proposer: A. Wiedenmann, HMI Berlin Dates of ExperimentExperimental Team: A. Rupp, HMI Berlin

A. Gorzel, HMI BerlinA. Wiedenmann, HMI Berlin

11.-14.06.2001


3He neutron spin filters allow to produce highlypolarised neutron beams over a wide range ofwavelengths (0.1Å to 16Å) [1]. They thereforepossess a high potential as polarising and analyserdevices used in the structure research of magneticmaterials. For this reason filter cell developmentplays an important role at the HMI (i.e. [2]).In order to demonstrate one of the experimentalpossibilities of this technique, the feasibility of arefillable filter cell for small angle neutronscattering applications was tested. The filter cellwas filled with polarised 3He at the filling station ofthe group of Prof. Heil (University of Mainz) to apressure of 490mbar and a polarisation of 50%.Inside a special transportation unit [3] it wastransported to the HMI and used on V4 with theSANSPOL option.The filter cell was used as analyser to separate thespin-flip from the non spin-flip scattering of a Co-ferrofluid in a magnetic field of B = 0.3Tperpendicular to the neutron beam. The samplecontaining 5% Co has been studied previously withSANSPOL [4]. The intensities for the twopolarisation states of incident neutrons (flipper onand off) with and without filter are compared inFig.1. Whereas the intensities for a scattering vectorQ perpendicular to the magnetic field are verysimilar with and without filter a clear difference isobserved for Q//H: The intensities are no longeridentical for flipper on and flipper of as expectedwhen no spin analysis is performed. With the filterspin-flip scattering is mainly observed with flipperon and non-flip scattering with flipper off. Weakspin-flip scattering is caused by magnetic momentswhich are not fully aligned in the weak magneticfield. Thus the spin analysis can reveal themagnetic ordering state of the ferrofluid. The cellshowed a relaxation time of 42h, while possessing atime constant of 50h about 7 months before. Thedecrease is probably due to ageing effects.

AcknowledgementWe are very grateful to Prof. Heil and his group atthe University of Mainz who enabled filling of ourfilter cell at their filling station.

The work has supported in parts by the EuropeanUnion through the RTD-TMR programme „CoolNeutron Optimisation” and the RTD-IHPprogramme ENPI.

Fig.1 spin-flip analysis of a Co-ferrofluid in a magnetic field of 0.3T with a refillable 3Hespinfilter cell

[1] J.Als-Nielsen et al., Phys.Rev. Vol.133,4B(1964), 925

[2] A. Danzig et al., Physica B 276-278 (2000),185-186

[3] A. Danzig, A. Rupp, Physica B 267-268(1999), 344

[4] A,: Wiedenmann, Physica B297(2001)226-233 see also this report

0.1 1

0.1

1

10

100

with filter, flipper off, Q//H with filter, flipper on, Q//H with filter, flipper off, Q perp.H without filter, fl. off, Q perp.H without filter, fl. off=on, Q//H


Scat

terin

g cr

oss-

sect

ion

[cm

-1]

214


EXPERIMENTAL REPORT Proposal N° *Instrument E1The use of a refillable 3He filter cell as neutron

polariser Local Contact J. Klenke

Principal Proposer: A. Rupp, HMI Berlin Dates of ExperimentExperimental Team: A. Rupp, HMI Berlin

A. Gorzel, HMI BerlinJ. Klenke, HMI Berlin

31.01.-04.02.200114.11.-18.11.200127.11.-30.11.2001


Nuclear-spin polarised 3He is a very efficientfilter material for neutrons. The strongly spindependent absorption of neutrons ( = 5b, = (2962 5.1)b[Å]) [1] allows to producehighly polarised neutron beams over a widerange of wavelengths (0.1Å to 16Å). For thisreason filter cell development plays animportant role at the HMI (i.e. [2]).First, in primary experiments, two HMI-maderefillable 3He filter cells were tested using themas an analyser and showed relaxation times of30.6h and 50h. Later on, also the feasibility ofa filter cell to be used as a polariser has beendemonstrated at E1.The filter cells were built and coated with Cs asdescribed in [3]. They were filled with polarised3He at the University of Mainz at the fillingstation of the group of Prof. Heil with apressure of 1bar. Inside a specialtransportation unit providing a homogenousguide field [4], they were transported to theHMI and placed at the sample position of E1.In the case of using the cell as a polariser,adiabatic spin rotation of the transmitted,axially polarised beam allowed the analysis ofthe neutron polarisation by a Heusler crystal.While the performance of the cell acting aspolariser turned out to be sufficient, themeasured relaxation time was not satisfying(fig.1). To improve this, the Cs coating of thatcell was subjected to a well-defined oxidationat RT to change it to Cs7O, which is known forits lower work function and thus shouldimprove the relaxation behaviour. Everythingelse in the set-up was kept unchanged.Fig.2 shows an increase of the time constantof about 10%. This demonstrates the potentialof Cs7O as an alternative coating material, butnevertheless, further efforts in filter celldevelopment are necessary. The magneticshielding of the transportation unit that wastested during the scattering experiments, cancompensate magnetic stray fields of at least40mT (fig.2).

Fig.1 : Decay of the 3He-polarisation in the Cs-coated filter cell

Fig.2: Decay of the 3He-polarisation in theCs7O-coated filter cell

Acknowledgement

We are very grateful to Prof. Heil and his group at theUniversity of Mainz who enabled filling of our filter cell attheir filling station.

The work has supported in parts by the European Unionthrough the RTD-TMR programme „Cool NeutronOptimisation” and the RTD-IHP programme ENPI.

References

[1] J. Als-Nielsen et al., Phys.Rev. 133,4B (1964), 925[2] A. Danzig et al., Physica B 276-278 (2000), 185-186[3] A. Rupp, A.Gorzel and J. Klenke, BENSC Experimental

Reports (2001)[4] A. Danzig, A. Rupp, Physica B 267-268 (1999), 344-347

0 20 40 60 80 100 120 1400,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

magneticstray field(40 mT)

Cs7O-coated filter cell

Tran

spor

tatio

n an

d ad

just

men

t

Exponential fitP0 = 32.8 %t1 = 24.9 h

3 He-

Pola

risat

ion

Elapsed time [h]

0 20 40 60 80 1000,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

Cs-coated filter cell

Tran

spor

tatio

nan

d ad

just

men

t

Exponential fitP0 = 43.4 %t1 = 21.9 h

3 He-

Pola

risat

ion

Elapsed time [h]

215

ef

EXPERIMENTAL REPORT Proposal N° EFInstrument E1Diffraction study of synthetic mica single

crystals Local Contact J. Klenke

Principal Proposer: H. Fritzsche, HMI Date(s) of ExperimentExperimental Team: H. Fritzsche, HMI

J. Klenke, HMI 06.09.01 - 07.09.01


Micas are aluminosilicate minerals with a sheetstructure with two layers of silicate tetrahedraarranged about an intervening layer of hydratedmetal-oxide octahedra. The interlayer space isoccupied by alkali (usually K) cations. Theinterlayer lattice spacing of about 1 nm is thelargest among minerals readily available in largecrystals, and is therefore of interest as a coldneutron monochromator or analyzer.

We investigated the properties of a synthetic fluoro-phlogopite of the form K2Mg6(Si3Al)2O20F4. Thesingle sheets were parallel to the sample surface.The sample had a thickness of 2.5 mm and an areaof 10 mm x 50 mm. We used a neutron wavelengthof 0.24076 nm for all experiments.

We performed -2 scans as well as rocking scansbut only for the reflections originating from thesheet structure. From the -2 scans we cancalculate an interlayer spacing of 0.997 nm. Therocking scans prove the high crystalline quality ofthe mica sample as can be seen e.g. for the (003)reflection in Fig. 1.

Fim

Tharofw

monochromators typically have a reflectivity ofabout 90%.

reflec-tion

FWHM / reflec-tivity

(001) 6.84 0.40 0.06 0.063(002) 13.90 0.28 0.02 0.008(003) 21.23 0.38 0.02 0.058(004) 28.94 0.27 0.01 0.008(005) 37.16 0.28 0.01 0.029

Tab. 1: Experimental data from the rocking scansperformed at the scattering angle ω with thecorresponding wavelength resolution ∆λ/λ.

_02 // brandt // 21.03.02 Seite 1 von 1

g. 1: Rocking scan around the (003) reflection,easured with 1 s per step.

e experimental data for all measured reflectionse listed in Table 1. Because of the low reflectivity about 6% these kind of mica crystals are not veryell suited as monochromators. Graphite

20 21 220

2000

4000

6000

8000

10000

12000

14000(003) reflection

Coun

ts

216


EXPERIMENTAL REPORT Proposal N° EFInstrument E9Asymmetry function at axially focusing

powder diffractometers Local Contact *

Principal Proposer: D. M. Többens, HMI Date(s) of ExperimentExperimental Team: D. M. Többens, HMI

1.-2.9.,13.-15.11.,10.-11.12.


The neutron powder diffractometer E9 uses anaxially focusing monochromator in combinationwith a wide detector opening in order to gainintensity. Common descriptions [1] of theasymmetry at this type of instrument considerthe effects from the heights of sample anddetector only. However, with an axialconvergence angle of about 7° from themonochromator this approximation is notsufficient. Incorrect modelling of peak shapesresults in a decreased quality of the overall fitand thus in decreased accuracy of the resultsas well as in the introduction of systematicerrors.

In order to overcome this problem a model forthe description of this beam geometry's peakshape has been derived (i.e. figure 1) and E9was used to test this model against actualpeak shapes [2].

Diffraction patterns had to be measured atvarious settings of the instrument, with well-resolved reflections over the whole 2θ-rangeand with high intensity so that counting

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statistics is negligible. Furthermore, theresolution resulting from the Caglioti functionshould be as good as possible in order tobetter accentuate the effects from the axialdivergence and the step wide must be small toallow the detection of systematic peak errors.A sample of about 10 g sintered corundumwas chosen and measured in high-resolutionmode with a step wide of 0.05° for about 24 hfor each instrumental setting. The resultingdiffraction patterns have about 80.000 countsmaximum intensity.

From these measurements, the parametersinfluencing the peak shape could be identified,taking into account the geometry of source,monochromator, sample and detector. Thefinal model results in peak shapes with verygood fit (figure 2) using only instrumentalparameters for the calculation of the axialaberration function.

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[1] L. W. Finger et al.: J. Appl. Cryst. 27, 892-900 (1994)[2] D. M. Többens, M. Tovar: Applied Physics A. MaterialScience & Processing, Supplement ICNS 2001, accepted

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PHY-02-0341-test // brandt // 23.03.02 Seite 1 von 1

EXPERIMENTAL REPORT Proposal N° PHY-02-341-testInstrument NRSE-V2Test of Spin-Echo Resolved Grazing Incidence

Neutron Scattering (SERGIS) Local Contact Klaus Habicht

Principal Proposer: J.Major, MPI-MF, Stuttgart Date(s) of ExperimentExperimental Team: Thomas Keller, MPI-FKF, Stuttgart

Suzanne te Velthuis, ANL, Argonne USAGian Felcher, ANL, Argonne USA

June 14-16, 2001

Date of Report: Jan. 29, 2002

The aim of the test was to provide the proof ofprinciple of the SERGIS method, using as asample a commercial optical grating.

In-plane correlations define the off-specularscattering pattern in neutron reflectometry.Conventional reflectometers with slit geometry,however, can resolve the scattering maps onlyin the scattering plane. The test was based onan idea [1,2] for labelling the neutron spin withthe direction (angle) of the neutron pathinstead of the usual energy (velocity) labelling.The directional labelling can be realized bytilted magnetic-field borders. By this way -even in the absence of in-plane collimation -we can obtain off-specular scattering maps formomentum transfers perpendicular to thescattering plane with very good angularresolutions.

We demonstrated the technical feasibility ofthe method at the FLEX-NRSE set-up at HMI[3]. In these experiments (cf. Fig. 1) acommercial optical grating was used assample, similar as previously used inconventional neutron reflectometryexperiments [4] and the results revealed theperiodicity of the grating (3600 lines/mm ~2778 Å, and, additionally, the profile of thegratings which was approximately sinusoidal.The detector collected all the intensitiesspecularly reflected or diffracted from thesample.

[1] M. Th. Rekveldt: Neutron Reflectometryand SANS by Neutron Spin Echo, Physica B234-236 (1997) 1135. [2] R. Pynn and F. Mezei, in: Neutron SpinEcho, ed. F. Mezei, Springer, Berlin, 1980.[3] T. Keller, R. Golub, F. Mezei, R. Gähler: Aneutron resonance spin-echo spectrometer(NRSE) with tiltable fields, Physica B 241-243(1998) 101.[4] R. M. Richardson, J. R. P. Webster, A.Zarbakhsh: Study of Off-Specular Neutron

reflectivity Using a Model System, J. Appl.Cryst. 30 (1997) 943.

Fig. 1: SERGIS results obtained on an opticalgrating K43-228 (Edmund Industrial Optics,USA) for = 0° (open squares), 0.5° (opencircles), and 90° (full symbols). is the anglebetween the mean neutron beam direction andthe gratings. The horizontal axis is proportionalthe NRSE frequency (spin-echo length), andthe vertical axis is the neutron spin polarizationas obtained by the spin echo. The datacorrectly reveal the periodicity of the structure(2778 Å), although several diffraction linescontribute to the measured polarization.

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Instrument NRSE-V2Spin-Echo Resolved Grazing IncidenceNeutron Scattering (SERGIS) Local Contact

Klaus Habicht

Principal Proposer: J.Major , MPI-MF, Stuttgart Date(s) of ExperimentExperimental Team: Gian Felcher, ANL, Argonne USA

Suzanne te Velthuis, ANL, Argonne USAThomas Keller, MPI-FKF, Stuttgart

29. 10. 2001 - 05. 11. 2001

Date of Report: January 29, 2002The aim of the experiment was the

systematic investigation of the Spin EchoResolved Grazing Incidence Scattering(SERGIS) of neutrons on a sample with ahighly precise periodic structure (an opticalgrating). A 2-dimensional position-sensitivedetector enabled us to obtain a full picture ofthe Bragg reflections of the grating. Suchexperiments were important for the fullunderstanding of the details of the SERGISmethod by recovering the full profile of theoptical grating and in the process defining itsinherent resolution properties.

Previously we had performed the proofof principle test of the SERGIS method[1]. Thisconsisted in adapting to an instrument with thegeometry of a reflectometer a NRSE circuit.Conventional reflectometers with slit geometryresolve the scattering maps only within thescattering plane. By using the neutron spin tolabel the direction (angle) of the neutron path,we can obtain off-specular scattering maps areobtained for momentum transfersperpendicular to the scattering plane with verygood angular resolution.

The present experiment examined thedetails of the SERGIS method in a systematicexperiment on a sample similar to the onepreviously used. This was a high quality gold-coated holographic grating (type 8306BK-520H, 3600 lines/mm; Thermo RGL,Rochester, NY) of surface 52 x 52 mm. Now a2-dimensional position-sensitive detectorenabled us to differentiate between the variousorders of the Bragg reflections by their differentvertical positions (the sample's surface washorizontal). The angle between the grating andthe neutron reflection plane, , was changedfrom 0o to 90o. Not only the intensities of thediffracted beams were detected for each valueof but also the phase of the neutronpolarization due to the mismatch in the neutronpaths before/after the sample for neutronsdiffracted by the optical grating.

We are now in the process ofreconstructing the diffraction potential on thebasis of a rigorous optical theory [2]. Already

from the raw data are visible at least twofeatures: 1) There is a drastic dependence ofthe diffracted intensities as a function of ,which seems to be a characteristic property ofdeeply grooved optical gratings. 2) The lateralcorrelation length is much longer thanexpected when viewed with conventionalscattering methods. The full analysis of thedata would provide us with sufficientinformation to design a more permanentSERGIS station dedicated to study more "real"samples. [1] Report on Proposal PHY-02-341-test. [2] W. A. Hamilton, A. G. Klein, G. I. Opat:Neutron Diffraction by Surface AcousticWaves, Phys. Rev. Lett. 58 (1987)2770.

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EXPERIMENTAL REPORT Eigenforschung

Instrument V4 – sensitivity of 3He – detectors for Timeof Flight measurement Local Contact

A. Wiedenmann/P. Strunz

Principal Proposer: K. Zeitelhack, TU München, ZWE – FRM II Date(s) of ExperimentExperimental Team: G. Montermann, R. Schneider ; Mesytec GbR

R. Gilles, B. Krimmer, TU DarmstadtP. Strunz, A. Wiedenmann, HMI Berlin

02.05.2001


The high resolution time-of-flight spectrometer TOF-TOF [1] at the New Neutron Source FRM-II in Garchingwill be equipped with an array of individual 3He-detec-tors placed on Debye-Scherrer cones. The whole arrayconsists of up to 1000 detectors (Dextray squashedseries) separated in four individual rows and covering ascattering angle from -15° - 140°.So far, these detectors were available with 3He/CO2(99/1) gas filling at p = 6bar maximum total pressure.Thus, for neutrons in the wavelength range 2Å < < 4Åthey have low detection efficiency ( = 63% - 86%).Moreover, the low stopping power of the gas mixture(rproton 8,3mm at p = 6bar calculated with TRIM[2] ) incombination with a low electron drift velocity ve (e.g.low electric field at detector edges) gives rise to a strongvariation of the signal rise time (rise 1µs – 4µs)observed depending on the neutron impact position andthe proton/triton track orientation. This limits the use offast readout electronics and increases deadtime and effi-ciency loss at the detector edges. Further on, it adds anon negligible contribtion to the intrinsic time resolutionof the detector.In close collaboration between FRM-II detectorlab andEurisys-Mesures we investigated several prototype de-tectors using 3He/CF4 mixtures as filling gas with totalpressure up to p = 10bar. High pressure, increased stop-ping power and drift velocity ve substantially reduce thedisadvantages mentioned above. However, they drasti-cally increase the -sensitivity of the detectors. In a 3h run at V4 a 1mm thick Cd-converter stopping thefocussed ( = 10mm) neutron beam ( = 12Å, IntensityIn = 2,4105 s-1 ) was used to produce a locally defined -source with an energy spectrum similar to the expectedexperimental -background at ToF-ToF. Each detectorunder investigation was mounted in a distance d = 95mmdownstream the converter and thus was exposed to anapproximate -fluence I 4104 s-1. Pulse height spectraof different prototype detectors were recorded incomparison to a standard 90NH40R squashed series

detector to study the individual n/-separation. Thedetectors were read out using a mesytec MRS2000module (charge sensitive preamplifier, square shaper(85% = 2,2µs) and window discriminator) and a mesytecMPSD/MCPD (8 bit ADC) data aquisition system. Fig. 1 shows the resulting pulse height spectrum of astandard 90NH40R squashed series detector with verylow -background . In comparison Fig. 2 shows the pulseheight spectrum recorded with a 120NH40RTF detectoroperated with 3He/CF4 (97/3) at p = 10bar.Fig.1: Pulse height spectrum of neutrons and ’s from

the Cd-converter recorded with a standard Dex-tray squashed series detector.

Fig. 2: Pulse height spectrum of neutrons and ’s fromthe Cd-converter recorded with a 120NH40RTFsquashed series prototype detector.

As expected a much higher -background is observed.However, with proper setting of the discriminator thres-hold (Thr = 20%) a -suppression > 105 can be deducedfrom the spectrum. This is in full agreement with therequirements of the ToF-ToF spectrometer.

References[1] A. Zirkel et al.,

Physica Scripta B, Vol. 276 – 278 (2000) 210[2] J.P. Biersack (HMI Berlin); J.F. Ziegler (IBM,

Yorktown); http://www.srim.org

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EXPERIMENTAL REPORT Proposal N° IAEA CRPInstrument V4An investigation into the performance of the

RUDETEC detectorLocal Contact A. Wiedenmann

Principal Proposer: J. Keshaw, Chris B. Franklyn (NECSA) SA Dates of Experiment

Experimental Team: J. Keshaw (NECSA), South AfricaA. Wiedenmann, HMI Th. Wilpert,11.-14.10.2002 HMI 12./13.06.2001


The detector constructed at NECSA’s RadiationUtilization Detector (RUDETEC) laboratory wastested at the HMI - V4 – SANS beam-line. The testgave some indication of the efficiency of thedetector, count-rate capability, linearity of positionvs. channel, MESYTEC electronic performance,and the suitability of the detection system forscattering experiments.It was found that the detector delivered an optimalefficiency of greater than 95% for 6Å and 12Å at abias high- voltage (HV) of 1010V. However, therewas a loss in position resolution at this HV due tothe accumulation of capture events that decentralisethe neutron capture position. This problem wasavoided; at the sacrifice of ~10% efficiency, at abias of 1080V, where the decentralising eventswere discarded by the data capture hardware. Aposition resolution FWHM of 1.980.33mm for a2mm Cd slit was recorded at an operating HV of1010V.Inconsistencies in efficiency (~20% as shown infig. 2) from neighbouring channels were found tobe a fault of the electronic ADC supplied. Thesewere rather stable problems and were removedfrom the data by software manipulation of theacquired spectra. However, inconsistencies of about3% still prevailed even after data manipulation. It ishoped that an improved electronic ADC would beprovided soon.The position vs. channel calibration (fig. 1) of thedetection system was found to be linear at0.6780.007mm per channel, with a usable activelength of about 1002mm.Diffraction measurements were carried out on aSilver Behenate sample at wavelengths of 6.05Åand 12.10Å. Results agreed well withmeasurements previously attained using the HMISANS facility detector (Table 1 below).

Table 1 – Summary of results obtainedfor the comparison of the peak positions obtained by previous experiments (literature), and those obtained by the spectra recorded

Fig. 1 – Position vs. Channel Straight line fit.

Fig. 2 – Position spectrum of the water sample showinginconsistencies produced by ADC problem

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EXPERIMENTAL REPORT Proposal N° IAEA-CRP*Instrument V4Test measurements on a linear position

sensitive detector Local Contact A. Wiedenmann

Principal Proposer: S. Messoloras, A. Wiedenmann Date(s) of ExperimentExperimental Team: K. Mergia, N.C.S.R. “Demokritos”

A. Wiedenmann, Th. Wilpert HMIA. Salevris, N.C.S.R. “Demokritos”

*1.-3.5.2001


The aim of the experiment was to carry testmeasurements on a 3He linear position sensitivedetector (RS-P4-0824-208) manufactured byReuter-Stokes in order to assess its performancefor use in Small Angle Neutron Scatteringinstruments. The detector is cylindrical of diameter 25.4 mm andwalls of 0.508 mm stainless steel. Its active lengthis 609.6 mm. The electronic arrangement systemused consisted of a PC, an I/O interface, theelectronics and the detector. Position encoding isbased on the charge division method.Two standard samples silver behenate (AgBE) andglassy carbon were measured at two differentwavelengths of 6.07 and 12.10 Å. For the measurement of the standard samples thedetector was placed vertically at a distance of 634mm from the sample position with the neutronbeam at the height of 285 mm from its down edge.A beam stop of boron carbide was placed on thedetector where the beam impinges on it.The collimation used was 4 m and the aperturewas 5 mm in diameter. The data were corrected forbackground, transmission and efficiency and finallyabsolute values were derived using watermeasurements. The water measurements werealso used for the detector efficiency corrections. The corrected data for AgBE at the twowavelengths λ=6.07 Å and λ=12.10 Å arepresented in fig.1. At this sample-detector distance,i.e. 634 mm, the FWHM of the peaks appearing atthe lower angles is 61.2 for λ=6.07 Å and 90.8 forλ=12.10 Å.The corrected data of glassy carbon measured atλ=6.07 Å are presented in fig. 2 (open circles). Forcomparison the data from the V4 detector areshown (open triangles). The difference indicatesnoticeable dead-time effects resulting from theelectronic settings.In addition the detector’s resolution was measuredusing the direct beam with 16 m collimation and anaperture of 2 mm in diameter. The detector wasplaced vertically on a height adjustment platform ata distance of 590 mm from the sample position.The beam profile on the detector was measured fortwo heights of the detector, i.e. with the neutronbeam impinging at distances s=165 mm and s=212mm from the detector center.

The beam profile was fitted by a Gaussian and theHWHM was found to be 17.8 for s=165 mm and19.2 for s=212 mm compared with the beam

Fig. 1. The corrected data of AgBE at two wavelengths6.07 and 12.10 Å.divergence =of 5.4'.

Fig. 2. The corrected data of glassy carbon at λ=6.07 Åfrom the test detector (open circles) and the V4 detector(open triangles).

The broadening corresponds to an intrinsicresolution of 6 mm.

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EXPERIMENTAL REPORT Proposal N°Eigenforschung

Instrument V4Position Sensitive Detector Tests at V4Local Contact A. Wiedenmann/P.Strunz

Principal Proposer: Ralph Gilles, TU Darmstadt/FRM-II Date(s) of ExperimentExperimental Team: B. Krimmer, TU Darmstadt

P. Strunz, A. Wiedenmann, HMI Berlin,K. Zeitelhack, TU München R. Schneider, G. Montermann, Mesytec

1.5. - 3.5. 2001


The new structure powder diffractometer SPODI at theFRM-II in Garching will be equipped with a positionsensitive detector (PSD) system. In principle this is anevolution of the individual counter array (ICA) used atsimilar facilities. The position sensitivity in the verticaldirection upgrades the ICA to a quasi 2D detector. Adrawback of a conventional angle-dispersive powderdiffractometer is that only a small part of the Debye-Scherrer cones is used. One way to overcome this is totake a 2D detector like image plates to record (as far aspossible) the complete rings. To obtain sufficientresolution only small sample sizes (diameter and height)can be tolerated. The use of collimators allows muchlarger sample sizes. The height is limited by thecurvature of the Debye-Scherrer rings within the detectoraperture.Each detector tube is made of stainless steel with anactive length of 300 mm and one inch diameter. The gasfill recipe is He3 at a partial pressure of 8 bar, Argon at apartial pressure of 4 bar and, a portion of 0.5 % CO2(specification sheet of the manufacturer Reuter&Stokes).He3 is virtually the counting gas, Argon is operating as astopping gas to improve position resolution and CO2works as a quencher. The position sensitivity is achievedby a resistive wire connecting the anode plugs on bothends of the tube. A nominal resolution of 2 mm isspecified by the supplier. The efficiency for thermalneutrons is about 50 %.For high gas amplification and in turn good signal-to-noise ratio the high voltage supply is 2000 V.

First measurements of the detectors and the Mesytecelectronics concerning position resolution including dataevaluation of the energy and the position signal of asingle detector and an ensemble have been performed.Fig. 1 shows eight single measurements at differentdetector positions to prove the resolution of the detector.In this the experiment a single detector was shiftedperpendicular to a pinhole neutron beam. Fig. 2 is theresult of a measurement with four single detectors in aunit to measure the cuts with Debye-Scherrer rings of asample called AgBE with lattice constant of around 58Å. FWHM of (001) reflection is 1.47° in not optimizedposition of resolution and comparable to measurementsof the V4 two-dimensional detector in highest resolutionset-up [1].

Fig.1: Position resolution measurements of a He3detector using Mesytec electronics.

Fig. 2: Measurements of AgBE powder with fourdetectors arranged in a two-dimensional area detector.

Reference

[1] R. Gilles, U. Keiderling, A. Wiedenmann, J. Appl.Cryst. (1998), 31, 957 - 959.

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EXPERIMENTAL REPORT Proposal N° PHY-04-667Instrument V6Discriminating between diffuse & specular

reflection using Neutron Spin EchoLocal Contact Helmut Fritzsche

Principal Proposer: Mike Fitzsimmons, Los Alamos National Lab Date(s) of ExperimentExperimental Team: Janos Major, Max-Plank-Institut

Roger Pynn, Los Alamos National LabM. Theo Rekveldt, Delft Univ. of Technology

Nov 4 – 11, 2001

Date of Report: Feb 15, 2002

Our experiment aimed to prove the viability of amethod, based on the neutron spin-echo (NSE)technique, to achieve good resolution along anarbitrary direction in (Q,E) space, without sacrificingsignal intensity. Although the method has generalapplicability to many neutron scatteringmeasurements, we applied it to the problem ofdiscriminating between diffuse scattering and specularreflection in neutron reflectometry. The technologicalbasis of the method is the availability of thin films ofeasily and completely magnetizable material that areof uniform thickness and do not depolarize neutronbeams. We used permalloy films electrodeposited onsilicon wafers and our experimental results showedthat the components made from these films worked asintended.

A sketch of the apparatus we used is shown in the twofigures below. The first is a perspective drawing whilethe second is a plan view. All rotator and precessionfilms were made from 30 microns of permalloydeposited on silicon wafers. The π/2 rotator films turnneutrons spins into and out of the precession plane(xz) or, when combined in the middle of theapparatus, cause a π rotation of spins about the x axis.The precession films indicated in the figures generatethe NSE spin precessions that allow specular anddiffuse reflection from the sample to be discriminated.Because each of the precession films has the samefield line integral along the z direction, specularscattering remains polarized while diffuse scattering isdepolarized by passage through the precession films,allowing the two types of scattering to bedistinguished.

Our measurements showed that: The π/2 rotator films and precession films

work as intended with little or no evidence ofincoherent beam depolarization;

We are able to detect changes in beampolarization caused by small angle scattering(such as might be caused by roughness of areflecting sample);

Precession films of somewhat greateruniformity in thickness will be needed for theapparatus sketched above to become widelyapplicable (current films have a thicknessvariation of +/- 0.2 microns whereas +/- 0.1microns is needed);

Other geometries for our apparatus are alsofeasible and these will not require filmuniformity greater than currently available.

This experiment has been written up and a papersubmitted to Reviews of Scientific Instruments.

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EXPERIMENTAL REPORT Proposal N° PHY-04-0681Instrument V12bUltra-small neutron deflections by sheets,

gratings and magnetic prism Local Contact W. Treimer

Principal Proposer: Apoorva G. Wagh, BARC, Mumbai 400085, India Date(s) of ExperimentExperimental Team: Apoorva G. Wagh, BARC, Mumbai 400085, India

Veer Chand Rakhecha, BARC, Mumbai 400085, IndiaWolfgang Treimer, BENSC, HMI, Berlin

14-19 Aug & 27 Aug-09Sep, 2001

Date of Report: 29 Jan 2002

We used 7 Ewald reflections each of 5.4 Åneutrons at the channel-cut monochromatorand analyser silicon crystals to record USANSspectra for a variety of samples.

Fig.1 displays USANS spectra for a bondpaper (squares), a single layer of tissue paper(circles), a kitchen aluminium foil (triangles), acadmium foil (inverted triangles), a trans-parency (diamonds) used in overhead project-ions and no sample (plus signs).

Fig. 2 compares USANS spectra obtained witha laser-cut cadmium grating of 0.5 mm period,for neutron incidence at its front (squares) andback (circles) faces, with the instrumentalrocking curve (triangles).

We inserted Si wedges within the monochro-mator and analyzer to attain (Fig.3) a sharperinstrumental rocking curve (circles). A magn-etic prism of 90o apex angle (vertical field ~1kOe in air between two permanent magnets) atthe sample position split the rocking curves forthe up and down spin states (squares).

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EXPERIMENTAL REPORT Proposal N° *Instrument V12aRefraction Data Based Tomographic

Imaging Local Contact W.Treimer, M.Strobl

Principal Proposer: W. Treimer, TFH Date(s) of ExperimentExperimental Team: M. Strobl, HMI

A. Hilger, TFHH.J. Peschke, TFH

Feb. – Jul. 2001

Date of Report: Jan. 2002

Introduction

As has been shown the V12a DoubleCrystal Diffractometer (DCD) can be used toregister refraction data as well as absorptiondata wiith tomographic scan measurements.But up to now the additional refractioninformation – compared to commontomography – could not be used directly forreconstructing and imaging of tomographicintersectional slides except in some veryspecial cases of simple and axis symmetriccylindrical samples [1]. However trying toreconstruct pure refraction data first promisingresults could be achieved.

Experimental

The data were recorded in the alreadyknown way [2], a whole scattering curve foreach scan point of 40 up to 60 projections over180° registered, integrated over the z-directioncaused by the only one dimensional positionsensitive detector. This one delivers theabsorption information by the integral over thetotal q range and the refraction information bythe shift of the point of gravity of the intensitydistribution. In the next step the tomographicintersectional image can be computed easilyfrom the absorption data using commonFiltered Back Projection (FBP) while this couldnot successfully directly applied onto refractiondata which is of different character then theabove. We therefore used differentmathematical modifications of the refractiondata and formed them to an “absorption-like”data set which could be used to reconstructdetails which would be invisible for commonabsorption tomography under the givencircumstances.

Results

The sample was an Al cylinder(diameter 15 mm, wholes 2 mm) scanned by aslit of 0,5 mm and the refraction based scan

shows the positions of the intersection in thesample while the common reconstruction ofabsorption data fails completely by the lack ofcontrast between air (holes) and Al

Fig. 1 Absorption and Refraction scan of one projection

Fig.1 (left diagram) shows the data of oneabsorption scan of one projection while theright diagram shows the refraction data of thesame scan in which the two holes can easilybe identified. Nevertheless its reconstructionsin Fig. 2 are not yet completely satisfyingalthough the data can be found to be of goodquality.

Fig. 2 Two reconstructions from refraction data

References

[1] W. Treimer, U. Feye-Treimer, C. Herzig,Physica B 241-243, (1998) 1197-1203

[2] W.Treimer, M.Strobl, BENSC Exp. Rep.2000, ISSN 0936-0891, S. 254

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EXPERIMENTAL REPORT Proposal N° *Instrument V12bRealisation of a DCD with 7- bounce

perfect crystals Local Contact W.Treimer, M.Strobl


A. Hilger, TFH Jan.,Feb. 2001

Date of Report: Jan 2002

Introduction

It is well known from the theory ofdynamical diffraction and realized by manyexperiments that by multiple reflection thereflection profile of a perfect Si crystal getsnarrower and its wings are suppressed. Forthis reason most of the DCDs operating asSANS instruments consist of triple bouncecrystals. In this work however 7-bouncechannel cut crystals were used for the first timeproviding almost perfect triangular rockingcurves.

For nearly zero absorption (Ewald solution) thereflectivity R of a single perfect crystal is givenby

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For a sevenfold reflection R becomes7E7E RR

Experimental results

The two special cut seven bouncechannel cut crystals (7-CCC, 111 reflection)were adjusted very carefully concerning the tiltof their net planes related to each other (betterthan 0,01°). The used wavelength of theneutron beam was measured to be=0,5248(2) nm which results in a theoreticand even so measured full width at halfmaximum (FWHM) of 5,7 arcsec. Theinstrumental rocking curve was recorded andcompared to theory as can be seen in thefigures. A nearly rectangular profile of theinstrumental rocking curve could be realised.Figs. 1a and 1b show the almost perfectaccordance of the theoretic with measured

instrumental curve compared to the resultingrocking curve of single reflecting crystals.

Figure 1a (above) 1b (below). Theory andMeasurement (linear and log.)

The deviations of the experimental curve fromthe theory can be explained by scattering ofthe neutron beam by the Cd (Gd) inserts ofthe channel cut crystals (see ref. [1])

References

[1] W. Treimer, M. Strobl, a. Hilger, Phys. Let. A289, 151-154 (2001)

-20 -15 -10 -5 0 5 10 15 20-0,1

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228


EXPERIMENTAL REPORT Proposal N° *Instrument V12bHigh resolution measurements

with seven bounce channel cut crystals Local Contact W. Treimer, M. Strobl


A. Hilger, TFH Jun., Jul., Aug. 2001


Introduction

The former introduced DCD equippedwith seven bounce channel cut crystals asmonochromator and analyser provides anextremely sharp instrumental curve with veryperfect triangular resolution function with a(FWHM) of 5.7 sec of arc and an impressingpeak to noise ratio of 105. [1] We demonstratethis feature and present some specialmeasurements.

Experimental results

A series of three very different sampleshas been recorded. For the first measurement(see Fig.1.) a single glass fibre with a diameterof 14 µm was exposed in the beam with awidth of 10 mm at the sample position. As asecond sample a simple Al wedge was usedwhich shall deviate the neutron beam exact 4arc seconds (Fig.2). At last a phase gratingconsisting of a d = 31 µm structure wasmeasured causing a diffraction pattern withmaxima roughly at each n times 3.5 arc sec(Fig. 3.) for the used wavelength of = 0.5248nm which can easily be seen from

dn

n

.

Results

The results for the first two samplesdemonstrate the high SANS intensity (Fig.1)and angular resolution of the instrument(Fig.2) while the third sample seems to be atthe limit of resolution possibilities (Fig.3).Although the main maxima can bedistinguished the minor maxima are notresolved (notice the third could be calculatedto be nearly suppressed). This can be donewith a reduced Darwin width of the resolutionfunction of the DCD (see next report). References

[1]. W. Treimer. M. Strobl, A . Hilger ,Phys Lett.A, 289, 151 – 154 (2001)

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229

cnr


EXPERIMENTAL REPORT Proposal N° *Instrument V12bEdge effects in a DCDLocal Contact W. Treimer, M. Strobl


A. Hilger, TFH Feb., Mar. 2001


Introduction

Experiments concerning high resolutiondouble crystal diffractometry (DCD) usingchannel cut crystals (CCC) showdiscrepancies between theoretical predictionand the wings of measured rocking curves. Toinvestigate the enhanced wing intensity theV12b DCD with its seven bounce CCCs wasused proving the idea that slit edges within theexperiments are able to cause contribution tothe wings by edge diffraction or evenrefraction.

Experimental

Various measurements were performedusing Cd and Gd slits and edges like they arenormally used in DCD experiments. The Cdedge has had a thickness of 1 mm and the Gdone of 0.25 mm. First measurements with Cdedges provided rocking curves with obviouslyenhanced wings compared to empty beammeasurements. But this effect was suspectedto be a combination of refracted neutronspassing through the Cd edge and diffractionand due to the presence of an edge in theneutron beam, both causing parasitic intensitywithin the wings of the rocking curve.

Results

The measurements with a Cd edgeunder different angels clearly demonstrate astrong effect of refraction while in the zeroposition still enhanced wing intensity waspresent that has to be explained by edgediffraction as can be seen from Fig. 1 despitethe fact that the edge geometry can also beblamed never to be perfect. Further resultsusing Gd edges are clear up this problem. InFig.2 the experimental points plotted and provethe edge diffraction. Due to the small effect ofone edge in the neutron beam the use offurther edges within the beam must enhancethe diffraction effect which definitely can

contributed to the edge diffraction. Note thatthe use of many edges has just an additiveeffect and definitely does not represent agrating because the geometry of the slits wasof the order of 1mm i.e. too big compared tothe coherence width of the neutron wave.

References

[1]. W. Treimer, M. Strobl, A.Hilger, Phys. Rev.Lett. (submitted)

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230


EXPERIMENTAL REPORT Proposal N° *Instrument V12bA tuneable channel cut crystalLocal Contact W. Treimer, M. Strobl


A. HIlger, TFH May, Jun., Jul. 2001


Introduction

The most important quantity in a doublecrystal diffractometer (DCD) responsible forthe resolution of the instrument is the full widthat half maximum (FWHM). The smaller it is thesmaller momentum transfers q i.e. the largerscattering structures are measurable. Onepossibility to reduce the FWHM is asymmetricBragg reflection which is on the other handconnected with a geometrical broadening ofthe beam and therefore also with andecreasing neutron flux density. An alternativeway of reducing and tuning the Darwin widthand with it the FWHM will be demonstratedhere.

Experimental

Special cut seven bounce channel cutcrystals (7-CCC) has been used asmonochromator and analyser of the DCD andwithin each 7-CCC a Si wedge deviates thebeam for some arc sec between the 3rd and 4th

reflecting crystal slab. This deviation causesa shift of the Darwin profiles of the fourfoldagainst the triple reflection creating a newDarwin range - (“Darwin reduction”),where means the full angular range of thetriple reflected Darwin pattern, for the crystals.The reduction value can additionally bevaried by rotating the wedges against thecrystal so that the FWHM can be tuned downto extreme small fractions of the naturalDarwin width which is 5.7 sec of arc in thiscase.

Results

Different curves with different wedges(Al, Si) have been recorded. Fig.1 showsexamples of different but symmetrical tuned Siwedges producing rocking curves down to aFWHM of 1.4 sec of arc. It is also possible totune just one crystal and hence to get curvessimilar to the Darwin pattern itself of the

second crystal. A further measurement with a31 µm phase grating performed with the tuned(1.4 arcsec) and un-tuned 7-CCC demon-

strates the feasibility of the new system as isshown in Fig. 2.

References

[1]. W. Treimer. M. Strobl, A . Hilger ,Phys Lett.A, 289, 151 – 154 (2001)

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FWHM = 5,9'' FWHM = 2,2'' FWHM = 1,7'' FWHM = 1,4''

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231



Instrument V 14New Solid State Neutron Optical ElementsLocal Contact Th. Krist

Principal Proposer: Th. Krist, HMI, H. Fritzsche, HMI Date(s) of ExperimentExperimental Team: Th. Krist, HMI, H. Fritzsche, HMI

2001


A solid state radial bender for the polarisation analysis ofneutrons over a wide angular range was built and testedat V6 and V 14 at BENSC. It consists of a bent stack ofSi wafers each of them coated with a polarisingsupermirror and an absorbing layer. The stack consistedof 19 channels which were tilted against each other by0.19°, thus a total angular interval of 3.8° could beanalysed.

Fig 1 Drawing of the radial bender with four of the 19 channels shown.

The device was put onto the detector arm of areflectometer with the bending axis of the bender parallelto the sample axis. With an incoming polarisation of98.7% a total flipping ratio of 70 and a transmission of60% of the spin up component were measured.

Fig 2 Transmission of neutrons with a wavelength of 4.72 Å throughthe radial bender for both neutron spin states together with thepolarisation efficiency as a function of the effective scattering angle.

Rotating the detector arm around the sample axis withouta sample inserted shows that the expected angular rangeof more than 3° can be analysed. The transmission hasan angular dependence due to an imperfect mechanical

set up of the bender. This effect does not occur for thedirection parallel to the channels where the geometryallowed to cover a range of 9.5° which can be analysed.With such benders neutron spins can be analysed forvery large solid angles in two dimensions for smallsamples. In another development we have built and tested at V14a radial collimator. Here a supermirror coated 75 mmlong collimator channel was opened at the downstreamend by inserting a thin slab of a silicon wafer. Since weused a polarising supermirror as wall coating it ispossible to measure the transmission of the radialcollimator with purely absorbing and with reflectingwalls for geometrically exactly the same set up. Thiscould be done because the spin down componentinteracts with a collimator with purely absorbing wallssince the supermirror coating is transparent for it whilethe spin up component reacts with the supermirrorcoating and is reflected from the walls. Fig. 3 shows thetransmission for the two spin components. The spindown component is reflected with high intensity onlywithin an angular interval of ± 0.4° with a maximumintensity at 0° because here is the least amount of siliconin the flight path. Beyond 0.4° the intensity drops to zeroat an angle of ± 0.78°. The spin up component interactswith the walls which reflect it up to 1°. Due to the wallinclination of ± 0.37° neutrons are transmitted up to± 1.37°. The transmitted intensity is 89% at 0° and dropsto about 75% at the critical angle of the supermirror.

Fig. 3 Transmission coefficient for neutrons with a wavelength of 4.72Å through a radial collimator channel formed by Si wafers coated witha FeCo-Si supermirror followed by a Gd layer, measured in a magneticfield of 300 Oe.

Such solid state neutron optical devices are smaller andlighter than their conventional counterparts and havevery well defined channels.

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232



Instrument V 14Development of neutron optical elementsLocal Contact

Principal Proposer: Th. Krist, HMI Date(s) of ExperimentExperimental Team: Sang-Jin Cho, HMI

Jan Hoffmann, HMI 2000


In 2000 a large amount of wafers coated withpolarising FeCo-Si supermirrors were tested. Thewafers are used in solid state benders at theinstrument LONGPOL at ANSTO, Sydney. The first batch of wafers delivered in 1997 had atransmission through the bender of 52%. Thewafers delivered in 2000 had a transmission of 59 ±4% averaged over 750 wafers. A maximum valueof 68% was reached for about 10% of the wafers.The polarisation of V 14 for the measurements in2000 was 92.8%, thus the spin up component was96.4% of the total beam intensity. Correcting forthis, the maximum experimental transmission was70.5%. The theoretical limit is given by theabsorption in Si and the transmission of the benderchannels. The absorption amounts to 20% for awavelength of 4.75 Å (16% for 3.6 Å, thewavelength used at LONGPOL). The transmissionamounts for the angular divergence of 0.03° used atV 14 to a value of 92% as calculated by thesimulation program SMAC2. With these values thetheoretical limit was 73.6%. Thus, in our benders96% of the theoretical value were reached.

In another set of experiments the interfaces inFeCo-Si multilayers were characterised at V 14.Structures with 10 bilayers were measured withpolarised neutrons. In Fig. 1 and 2 data are shownfor one of them with thicknesses of 100 Å FeCoand 100 Å Si together with simulations made usingthe program PARRAT. Between the layers of FeCo and Si interface layersare clearly visible from the simulation. Theirthicknesses are 14.7 ±0.5 Å on the FeCo layer and13.3 ±0.5 Å on the Si layer. The respectivescattering length densities for neutrons are alsoderived from the simulations. They amount for thelayers on FeCo to 781 µm-2 for the spin upcomponent and to 511 µm-2 for the spin downcomponent and for those on Si to 609 µm-2 for bothcomponents. Thus the interface layer on FeCo ismagnetic, the other not. From the density diagram of mixtures of Fe and Sithe atomic density and together with theinformation about the magnetisation of thesemixtures the scattering length densities can be

calculated. Using these values the compositions ofthe interface layers can be evaluated. This leads toFeCo49Si51 for the layer on FeCo and to FeCo65Si35for the layer on Si. Both values are very close to theexpected stoichiometric compositions of FeCoSiand FeCo2Si which were also confirmed with othermethods.

Fig. 1 Neutron reflectivity for spin up neutrons with = 4.75Åfrom a FeCo-Si multilayer with simulation.

Fig. 2 Neutron reflectivity for spin down neutrons with = 4.75Å from a FeCo-Si multilayer with simulation.

0.00 0.02 0.04 0.06 0.08 0.101E-4

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Simulations with interface layers without interface layers

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233

235

Part II

LIST OF PUBLICATIONS

Papers 236 - 252

Conference Contributions & Seminar Talks 253 - 277

Theses 278 - 279

BENSC Experimental Reports 2001 Part II, List of Publications

Publications 2001BENSC Experiments and BENSC Authors

236

2000 (supplement)

Eskildsen, M. R.; Nørgaard, K.; Abrahamsen, A. B.;Andersen, N. H.; Mortensen, K.; Gammel, P. L.;López, D.; Bishop, D. J.; Vorderwisch, P.; Meissner,M.; Canfield, P. C.:Neutron scattering studies of the flux line latticeand magnetic ordering in TmNi2B2C.Kluwer academic publishers, Proceedings of theNATO Advanced Research Workshop on Rare-Earth Transition Metal Borocarbides (Nitrides):Superconducting, Magnetic and Normal State Pro-perties, Dresden June 14-17, 2000, pp. 333-340

Fiori, F.; Iaccarino, M.; Quadrini, E.:Mechanical and microstructural characterisationof sintered components obtained by net-shapeforming from metallic powders7th Int. Conf. On Composites Engineering (ICCE-7),Denver, Colorado (USA), 2-8/7/2000, p. 235 (pro-ceeding)

Knorr, K.; Braunbarth, C.M.; v.d. Goor, G.; Behrens,P.; Griewatsch, C.; Depmeier, W.:High pressure study on dioxolane silica sodalite(C3H6O2)2[Si12O24] - neutron and X-ray powderdiffraction experimentsSolid State Communications 113 (2000) 503-508

Knorr, K.; Depmeier, W.:The Kiel/Berlin cells for neutron powderdiffractionHigh Pressure Research 17 (2000) 297-303

Löffler, J.F.; Braun, H.-B.; Wagner, W.:Magnetic correlations in nanostructured ferromag-netsPhysical Review Letters. 85 (9) (2000) 1990-1993

Mikulina, O.; Lacerda, A.H.; Kamarad, J.; Nakotte,H.; Beyermann, W.P.; Sechovsky, V.; Prokes, K.;Menovsky, A. A.:Electrical resistance and magnetism in UNiAlunder pressure and magnetic fieldsScience and Technology of High Pressure, editedby Murli H. Manghnani, William J. Nellis andMalcolm F. Nicol, Universities‘ Press, Hyderabad(2000) 730-733

Scheffer, M.; Rouijaa, M.; Suck, J.-B.; Sterzel, R.;Lechner, R. E.:Magnetic neutron scattering from quasicrystalli-ne Zn-Mg-Ho and Zn-Mg-Y at low temperaturesMaterials Science and Engineering 294-296 (2000)488-491

Soetens, J.C.; Desmedt, A.; Guillaume, F.; Harris,K.D.M.:Molecular dynamics simulation study of cyclo-hexane guest molecules in the cyclohex-ane / thiourea inclusion compoundChem. Phys. 261 (2000) 125-135

Török, Gy.; Lebedev, V.T.; Cser, L.;Zrinyi, M.:NSE-study of magnetic phase dynamics in po-ly(vinylalcohol) ferrogelPhysica B 276-278 (2000) 396-397

Török, Gy.; Lebedev, V.T.;Cser, L.; Buyanov, A.L.;Revelskaya, L.G.:Macrojunctions ordering in polyelectrolyte hy-drogelsPhysica B 276-278 (2000) 398-399

2001

Andreev, A. V.; Divis, M.; Javorsky, P.; Javorsky,P.; Sechovsky, V.; Kunes, J.; Shiokawa, Y.:Electronic structure and magnetism in UPtAlPhys. Rev. B 64 (2001) 144408

Aris, S.; Martins, R.V.; Merino, J.M.; Pyzalla, A.:Simulation of deformation textures and crystal-lite microstrains of cubic metals and compari-son to experimental resultsProceedings 2000, Materials Week 2001, 1.-4.10.2001, ICM München (www.materialsweek.org)

Aris , S .; Ma rtins, R .V.; W eg ene r, J.; H onk im äki, V .;Py za lla , A .:Te xture an d cry sta llite microstrain dev elo pm entdu ring ten sile deformation o f c opp er - sim ulationan d compa rison to e xpe rim en tal re su lts –J. d e P hys iq ue IV Vo l. 1 (2 00 1) pp. P r 4 –61 – Pr 4-68

Arrighi, V.; Ferguson, R.; Lechner, R. E.; Telling, M.;Triolo, A.:Local dynamics of atactic polypropylene acrossthe glass transitionPhysica B 301 (2001) 35-43

Arrighi, V.; Pappas, C.; Triolo, A.; Pouget, S.:Temperature dependence of local chain dynam-ics in atactic polypropylene: A neutron spin-echo studyPhysica B 301 (2001) 157-62

Auffermann, G.; Prots, Y.; Kniep, R.:SrN and SrN2: diazenides by synthesis underhigh N2-pressureAngew. Chem. Int. Ed. 40 (2001) 547- 549Angew. Chem. 113 (2001) 565 - 567

Baran, S.; Hofmann, M.; Lampert, G.; Stüsser, N.;Szytula, A.; Többens, D.; Smeibidl, P.; Kausche, S.:Neutron diffraction studies of the magneticstructures of HoAuGe and ErAuGeJ. Magn. Magn. Mat. 236 (2001) 293-301

Baran, S.; Hofmann, M.; Stüsser, N.; Szytula, A.;Smeibidl, P.; Kausch, S.:Neutron diffraction studies of magnetic orderingin cubic ErAuSnJ. Magn. Magn. Mat. 231 (2001) 94-97



237

Bazela, W.; Gondek, L.; Penc, B.; Szytula, A.;Stüsser, N.; Zygmunt, A.:Magnetic structures and magnetic phase transi-tions in RAuIn (R=Tb,Ho) compoundsActa Physics Polonica B 32 (2001) 3387-3392

Beiner, M.; Kahle, S.; Abens, S.; Hempel, E.; Hö-ring, S.; Meißner, M.; Donth, E.:Low-temperature heat capacity, glass transitioncooperativity and glass structure vault break-down in a series of poly (n-alkyl) methacrylatesIn: Macromolecules 34 (2001) 5927-5935

Böhmert, J.; Ulbricht, A.; Kryukov, A.; Nikolayev, Y.;Erak, D.;Composition effects on the radiation embrittle-ment of iron alloysEffects of radiation on Materials: 20th Int. Sympo-sium, ASTM STP, eds.: S.T. Rosinski, L. Gross-beck, T.R. Allen, A.S. Kumar, 1405 (2001) 383-398

Böhmert, J.; Viehrig, H.-W.; Ulbricht, A.:Irradiation effects on toughness behaviour andmicrostructure of VVER-type pressure vesselsteelsJ. Nucl. Mater. 297 (2001) 251-261

Brome, C.R.; Butterworth, J.S.; Dzhosyuk, S.N.;Mattoni, C.E.H.; McKinsey, D.N.; Doyle, J.M.; Huff-man, P.R; Dewey, M.S.; Wietfeldt, F.E.; Golub, R.Habicht, K.; Greene, G.L.; Lamoreaux, S.K.; Coak-ley, K.J.:Magnetic trapping of ultracold neutronsPhysical Review C 63 (2001) 1-15

Bu slaps , T .; Aris, S .; Martins, R.V.; H onk im äki, V .;Py za lla , A .:In ve stigatio n o f tex ture a nd in tergranu lar s tra ins of a lum inu m and stee l u sin g hig h e ne rgy sy nc hro-tron ra dia tion and c omp ariso n to n um erical m od-elsJ. M ate ria ls Proce ss . T ech no log y 11 7 (3) (2 001 ) CD –RO M

Cavadini, N.; Henggeler, W.; Furrer, A.; Güdel ,H.U.; Krämer, K.; Mutka, H.; Wildes, A.; Vorder-wisch, P.:Quantum magnetic phase transition: A top-downapproachILL Annual Report 2000 (ILL, Grenoble 2001) 12-13

Chang, S.; Jung, M.H.; Nakotte, H.; Brück, E.;Klaasse, J.C.P.; Mihalik, M.: Lacerda, A.H.; Prokes,K.; Torikachvili, M.S.; Schultz, A.J.:Electronic properties of UIrGe in high magneticfields.J. Appl. Phys. 89 (2001) 7186-7188

Charalambopoulou, G.Ch.; Steriotis, Th.A.; Stefa-nopoulos, K.L.; Stubos, A.K.; Kanellopoulos, N.K.;Mitropoulos, A.Ch.; Hauss, Th.:

Membrane neutron diffraction: A promisingtechnique for stratum corneum structural stu-diesJ. Contr. Rel. 72 (1-3) (2001) 307-309

Chatterji, T.; Regnault, L.P.; Thalmeier, P.; van deKamp, R.; Schmidt, W.; Hiess, A.; Vorderwisch, P.;Suryanarayanan, R.; Dhalenne, G.; Revcholevschi,A.:Spin dynamics of quasi-2D ferromagnetLa1.2Sr1.8Mn2O7

J. of Alloys and Compounds 326 (2001) 15-26

Danilkin, S.; Fuess, H.; Wieder, T.; Hoser, A.:Phonon dispersion and elastic constants in Fe-Cr-Mn-Ni austenitic steelJ. of Materials Science, 36 (2001) 811-814

Desmedt, A.; Guillaume, F.; Combet, J.; Dianoux,A.J.:A high resolution quasielastic neutron scatter-ing study of the guest molecules dynamics inthe cyclohexane / thiourea inclusion compoundPhysica B 301 (2001) 59-64

Desmedt, A.; Kitchin, S.J.; Guillaume, F.; Couzi, M.;Harris, K.D.M.; Bocanegra E.:Phase transitions and molecular dynamics inthe cyclohexane / thiourea inclusion compoundPhys. Rev. B 64(5) (2001) 054106 (1-21)

Dieter, S.; Pyzalla, A.; Reimers, W.:Textur- und Eigenspannungsanalysen an Ver-schleißschutzschichten für MikrozahnräderIn: “Material- und Verfahrensentwicklung für mikro-technische Hochleistungsbauteile”, Ed. K.-H. ZumGahr, Wissenschaftliche Berichte des Forschungs-zentrums Karlsruhe, FZKA 6662 (2001) 79-82

Dieter, S.; Pyzalla, A.; Wanderka, N.; Macht, M.-P.;Reimers, W.:Eigenspannungen, Textur und Koerzitivfeld inAbhängigkeit von den Sputterparametern fürFeCo/SiO2 – SchichtenIn: “Material- und Verfahrensentwicklung für mikro-technische Hochleistungsbauteile”, Ed. K.-H. ZumGahr, Wissenschaftliche Berichte des Forschungs-zentrums Karlsruhe, FZKA 6662 (2001) 35-40

Ehlers, G.; Casalta, H.; Lechner, R. E.; Maletta, H.:Dynamics of frustrated magnetic moments inantiferromagnetically ordered TbNiAl probed byneutron time-of-flight and spin-echo spectros-copyPhys. Rev. B 63 (2001) 224407-1 –224407-6

Ehlers, G.; Farago, B.;. Pappas, C.; Mezei, F.:A new IN11 with an almost 35 times highercounting rate than that of IN11CProceedings of the ILL Millenium Workshop, 2001 p.316



238

Enderle, M.; Roennow, H.M.; McMorrow, D.F.; Reg-nault, L.-P.; Dhalenne, G.; Revcholevschi, A.;Vorderwisch, P.; Schneider, H.; Smeibidl, P.;Meissner, M.:Excitations of the field-induced quantum solitonlattice in CuGeO3

Phys. Rev. Lett. 87 (2001) 177203

Enderle, M.; Roennow, H.M.; McMorrow, D.F.; Reg-nault, L.-P.; Vorderwisch, P.; Meissner, M.;Smeibidl, P.; Dhalenne, G.; Revcholevschi, A.:Statics and dynamics of the magnetic solitonlattice in the high-field phase of CuGeO3

J. Magn. Magn. Mat. 226-230 (2001) 465

Fahr, T.; Trinks, H.-P.; Schneider, R.; Fischer, C.:Investigation of the formation of the Bi-2223phase in multifilamentary Bi-2223/Ag tapes by insitu high temperature neutron diffractionIEEE Transactions on Applied Superconductivity 11(1, pt.3) (2001) 3399-402

Faraone, A.; Magazù, S.; Lechner, R. E.; Longeville,S.; Maisano, G.; Majolino, D.; Migliardo, P.; Wan-derlingh, U.:Quasielastic neutron scattering from trehaloseaqueous solutionsJ. Chem. Phys. 115 (2001) 3281-3286

Feyerherm, R.; Mathonière, C.; Kahn, O.:Magnetic anisotropy and metamagnetic behav-iour of the bimetallic chain MnNi(NO2)4(en)2, (en= ethylenediamine)J. Phys.: Condens. Matter 13 (2001) 2639-2650

Fiori, F.; Bruno, G.; Carradò, A.; Dunn, B.; Girardin,E., Pirling; T.:Determination of residual stresses in Ti6Al4Vwelded plates using neutron diffractionProc. ILL Millennium Symposium, Grenoble, 6-7/4/2001, p. 264 (proceeding)

Fitter, J.; Herrmann, R.; Dencher, N.A.; Blume, A.;Hauß, T.:Activity and stability of a thermostable a-amylasecompared to its mesophilic homologue: Mecha-nisms of thermal adaptation.Biochemistry 40 (2001) 10723 - 10731

Fitter, J.; Herrmann, R.; Hauß, T.; Lechner, R. E.;Dencher, N. A.:Dynamical properties of a-amylase in the foldedand unfolded state: the role of thermal equilibri-um fluctuations for conformational entropy andprotein stabilisationPhysica B 301 (2001) 1-7

Fitzsimmons, M. R.; Leighton, C.; Hoffmann, A.;Yashar, P. C.; Nogués, J.; Liu, K.; Majkrzak, C. F.;Dura, J. A.; Fritzsche, H.; Schuller, I. K.:Influence of interfacial disorder and temperatureon magnetization reversal in exchange-coupledbilayers.

Phys. Rev. B 64 (2001) 104415

Funk, T.; Brewer, W.D.; Kapoor, J.; Kirsch, R..;Metz, A.; Riegel, D.:Experiments on the magnetism of Sc implantedinto metalsHyp. Int., 133 (2001) 253

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Stüsser, N.; Ding, Y.; Hofmann, M.; Reehuis, M.;Ouladdiaf, B.; Ehlers, G.; Günther, D.; Meißner, M.;Steiner, M.:Evidence for interpenetrating magnetic structu-res across an IC-C phase transition inMn0.88Fe0.12WO4


Szytula, A.; Hofmann, M.; Leciejewicz, J.; Penc, B.;Zygmunt, A.:Magnetic properties and magnetic structures ofRIrSi (R=Tb-Er) series of compoundsJ. of Alloys and Compounds 316 (2001) 58-63

Szytula, A.; Jaworska-Gotab, T.; Baran, S.; Penc,B.; Leciejewicz, J.; Hofmann, M.; Zygmunt, A.:Magnetic structure of HoPd2Si2 redefined on thebasis of new neutron diffraction dataJ. of Physics: Condensed Matter 13 (2001) 8007-8014

Tanaka, H.; Oosawa, A.; Kato, T.; Uekusa, H.;Ohashi, Y.; Kakurai, K.; Hoser, A.:Observation of field-induced transverse NéelOrdering in the spin gap system TlCuCl3J. Phys. Soc. Jpn. 70 (4) (2001) 939-942

Temst, K.; van Bael, M. J.; Fritzsche, H.:Application of off-specular polarized neutronreflectometry to measurements on an array ofmesoscopic ferromagnetic disksAppl. Phys. Lett. 79 (2001) 991-993

Temst, K.; van Bael, M. J.; Fritzsche, H.:Neutron reflectivity study of a magnetic dotarrayJ. Magn. Magn. Mat. 226-230 (2001) 1840-1841

Többens, D. M.; Depmeier, W.:Superstructure of strontium chromate aluminatesodalite at low temperaturesZeitschrift für Kristallographie 216 (2001) 586-590

Többens, D. M., Depmeier, W.:The intermediate phase of strontium chromatealuminate sodaliteZeitschrift für Kristallographie 216 (2001) 611-615

Többens, D. M.; Stüßer, N.; Knorr, K.; Mayer, H. M.;Lampert, G.:E9: The new high-resolution neutron powderdiffractometer at the Berlin Neutron ScatteringCenterMater. Sci. Forum. 378-381 (2001) 288-293

Többens, D. M.; Stüßer; N.:E9: The new high-resolution neutron powderdiffractometer at BENSCNeutron News 12.3 (2001) 28-32

Toda, M.; Goto, T.; Chiba, M.; Ueda, S.; Nakajima,K.; Kakurai, K.; Feyerherm, R.; Hoser, A.;Graf, H. A.; Steiner, M.:Neutron diffraction study of field-induced-orderin singlet-ground-state magnet CsFeCl3J. Phys. Soc. Jpn. 70 Suppl. A (2001) 154-156

Török,Gy.; Lebedev, V.T.; Cser, L.; Orlova, D.N.;Kali, Gy.; Sibilev, A.I.; Alexeev, V.L.; Bershtein,V.A.; Budtov, V.P.; Zgonnik, V.N.; Vinogradova,L.V.; Melenevskaya, Yu, E.:NSE-study of fullerene-containing polymersPhysica B 297 (2001) 45-49

Török, Gy.; Lebedev, V.T.; Cser, L.;Kali,Gy.;Zrinyi, M.:Dynamics of PVA-gel with magnetic macrojunc-tionsPhysica B 297 (2001) 40-44

Treimer, W.; Strobl, M.; Hilger, A.:Development of a tunable channel cut crystalPhys. Lett. A 289 (2001) 151 – 154

Treimer, W.; Feye-Treimer, U.; Strobl, M.:Doppelkristalldiffraktometrie und TomographiePSI – Proceedings 01-01, Mai (2001) pp. 26 – 29

Treimer, W.; Strobl, M.; Hilger, A.:Experiments with tuneable many bounce chan-nel cut crystals for thermal neutron scatteringProceedings of euspen, 2nd Int. Conf. Vol 1 (2001)pp. 526 – 529

Triolo, A.; Arrighi, V.; Triolo, R.; Passerini, S.;Mastragostino, M.; Lechner, R. E.; Ferguson, R.;Borodin, O.; Smith, G. D.:Dynamic heterogeneity in polymerelectrolytes.Comparison between QENS data and MD simu-lationsPhysica B 301 (2001) 163-167

v. Klitzing, R.; Leiner, V.; Steitz, R.:Neutron reflectivity measurements on polyelec-trolyte multilayers at the solid/liquid interfaceILL Millenium Symposium & European User Meet-ing, Proceedings (2001) 73-75

Wagh, A.; Rakecha, V. C.; Treimer, W.:Bonse-Hart angular profiles realized for multiplyBragg reflected neutronsPhys. Rev. Lett. 87 (12) 125504-1 – 4 (2001)

Weissmuller, J.; Michels, D.; Michels, A.; Wieden-mann, A.; Krill, C.E.; Birringer, R.:Magnetic small-angle neutron scattering bynanocrystalline terbiumScripta Materialia 44 (2001) 2357-2361

Wiedenmann, A.:Small angle neutron scattering investigations ofCo Ferrofluides using polarised neutrons



245

Magnetohydrodynamics 37(3) (2001) 236-242

Wiedenmann, A.:Small angle neutron scattering investigations ofmagnetic nanostructures and interfaces usingpolarised neutronsPhysica B 297 (2001) 226-233

Wiedenmann, A.:Overview of current SANS facilities and theproposed research1. Coordination meeting on Development and prac-tical utilization of SANS applicationsIAEA report (2001) Vienna, Austria

Wilmer, D.; Feldmann, H.; Combet, J.; Lechner,R.E.:Ion conducting rotor phases— new insightsfrom quasielastic neutron scatteringPhysica B 301 (2001) 99-104

Yamazaki, H.; Tanaka, Y.; Matsuda, M.; Katsumata,K; Reehuis, M.: Magnetic structures of an Er/Tb superlatticestudied by neutron diffractionPhys. Stat. Sol. (b) 228 (2001) 741

Zhang, H.; Campbell, S.J.; Li, H.S.; Yan, Q.W.; Wu,E.; Hofmann, M.:Magnetization study of rare-earth intermetalliccompounds R3Co29Si4B10

Physica B 305 (2001) 10

Zheludev, A.; Honda, Z.; Katsumata, K.; Feyerherm,R.; Prokes, K.:Field-induced commensurate long-range orderin the Haldane-gap system Ni(C5H14N2)2N3(ClO4)Europhys. Lett., 55 (2001) 868-873

Zsigmond, G.; Lieutenant, K.; Manoshin, S.;Mezei, F.:VITESS simulation of backscattering and reflec-tometry at spallation sourcesProceedings of Int. Workshop on New Opportunitiesin Single Crystal Spectroscopy with Neutrons,Balaton, Hungary, April, 19-22, 2001, p. 87

Zsigmond, G.; Streffer, F.; Wechsler, D.; Mezei, F.:Monte Carlo simulation of crystal monochroma-tors/analysers - Applications for backscatteringspectroscopy with high resolutionProceedings of ICANS-XV (2000) (Eds. J. Suzukiand S. Itoh, JAERI, Tsukuba, 2001) Vol. I, p. 354

Zsigmond, G.; Wechsler, D.; Mezei, F.:Monte Carlo simulation of NSE at reactor andspallation sourcesProceedings of ICANS-XV (2000) (Eds. J. Suzukiand S. Itoh, JAERI, Tsukuba, 2001) Vol. I, p. 400

Zsigmond, G.; Mezei, F.; Wechsler, D.; Streffer, F.:

Monte Carlo simulation of crystal monochroma-tors/analysers - applications for the crystal-analyser neutron spectrometer IRISNucl. Instr. and Meth. In: Phys. Res. A, 457/1-2(2001) 299-308

2002 preview

Alava, C.; Arrighi, V.; Cameron, J.D.; Cowie, J.M.G.;Moeller, A.; Triolo, A.; Vaqueiro, P.: SANS studies of solutions and molecular com-posites prepared from cellulose tricarbanilateAppl. Phys. A (2002) accepted

Alsmadi, A.M.; Chang, S.; Jung, M.H.; Lacerda,A.H.; Brück, E.; Prokes, K.; Nakotte, H.:Magnetorezistance of UIrGe under high pressureKluwer Academic Publishers: NATO Sciences se-ries (2002) in print

Alsmadi, A.M.; Sechovsky, V.; Lacerda, A.H.;Prokes, K.; Kamarad, J.; Brück, E.; Chang, S.;Jung, M.H.; Nakotte, H.:Hybridization and pressure effects in UTX com-poundsAppl. Phys. A (2002) in print

Annibali, G.; Bruno, G.; Giuliani, A.; Manescu, A.;Marcantoni, M.; Fiori, F.; Turquier, F.:Neutron diffraction measurements for residualstress analysis in automotive steel gearsAppl. Phys. A (2002) accepted

Arialdi, G.; Karatasos, K.; Ryckaert, J.-P.; Arrighi,V.; Saggio, F.; Triolo, A.; Desmedt, A.; Pieper, J.;Lechner, R.E.:Local dynamics of polyethylene and its oli-gomers: A molecular dynamics interpretation ofthe incoherent dynamic structure factorMacromolecules (2002) submitted

Baglioni, P.; Berti, D.; Dante, S.; Fratini, E.; Hauss,T.:A structural study of lamellar phases formed byNucleoside Functionalized LipidsAppl. Phys. A (2002) accepted

Baldelli Bombelli, F.; Berti, D.; Keiderling, U.;Baglioni, P.:Living polynucleotides formed by the spontane-ous aggregation of dilauroylphospholiponu-cleosidesAppl. Phys. A (2002) accepted

Baran, S.; Hofmann, M.; Lampert, G.; Stüsser, N.;Szytula, A.; Többens, D.; Smeibidl, P.; Kausche, S.:Magnetic structures of HoAuGe and ErAuGeAppl. Phys. A (2002) accepted

Batko, I.; Flachbart, K.; Kohout, A.; Matas, S.;Meschke, M.; Siemensmeyer, K.; Schitsevalova, N.;



246

Paderno, Y.:Magnetic order in the fcc-symmetry: phasediagram and structure of ReB12Appl. Phys. A, accepted

Bazela, W.; Gondek, L.; Penc, B.; Stüßer, N.;Szytula, A.; Zygmunt, A.:Magnetic order in RAuIn (R=Tb, Dy, Ho) com-poundsAppl. Phys. A (2002) accepted

Beirne, E.D.; McEwen, K.A.; Habicht, K.; Fort, D.:Magnetic Excitations in Single Crystal PrNiSnAppl. Phys. A (2002) accepted

Beltsios, K.; Steriotis, Th.; Stefanopoulos, K.L.;Kanellopoulos, N. K.:Chapter 6: membrane science and technologyHandbook of porous solids, ed. F. Schüth, K Singand J. Weitkamp, Whiley V.C.H., in press

Bernal, S.; Blanco, G.; Cifredo, G. A.; Delgado, J. J.;Finol, D.; Gatica, J. M.; Rodriguez-Izquierdo, J. M.;Vidal, H.; Hoser, A.:Investigation by means of H2 adsorption, dif-fraction and electron microscopy techniques ofa cerium/terbium mixed oxide supported on alanthana-modified aluminaChem. Mater. 14 (2002) 844-850

Berti, D.; Fratini, E.; Dante, S.; Hauß, T.;Baglioni, P.:A structural study of lamellar phases formed bynucleoside functionalized lipidsAppl. Phys. A (2001) in press

Berti, D.; Keiderling, U.; Baglioni, P.:Supramolecular structures formed by phos-pholiponucleosides: aggregational propertiesand molecular recognitionColloid and Polymer Science (2002) in press

Bonn, S.; Fritzsche, H.; Hauschild, J.; Klenke, J.;Maletta, H.:Spin density waves of thin epitaxial Cr(110)layers in a V/Cr multilayerAppl. Phys. A, accepted

Bouchard, P.J.; Fiori, F.; Treimer, W.:Characterisation of creep cavitation damage in apressure vessel stainless steel using smallangle neutron scatteringAppl. Phys. A (2002) accepted

Bruno, G.; Fiori, F.; Girardin, E.; Giuliani, A.;Koszegi, L.; Levy-Tubiana, R.; Manescu, A.;Rustichelli, F.:Residual stress determination in several MMCsamples submitted to different operating condi-tionsJ. of Neutron Research (2002) in print

Bruno, G.; Girardin, E.; Giuliani, A.; Manescu, A.;Rustichelli, F.; O'Donnell, B.; McHugh, P.E.:Residual stresses in aerospace MMC materialsby neutron diffractionAppl. Phys. A (2002) accepted

Calandrini, V.; Deriu, A.; Onori, G.; Lechner, R. E.;Pieper, J. :Dynamic features of hydration water interactingwith hydrophobic moleculesAppl. Phys. A (2002) accepted

Calandrini, V.; Deriu, A.; Onori, G.; Lechner, R.E.;Pieper, J.:Water dynamics in dilute aqueous solutions ofsmall apolar solutes by quasi-elastic neutronscatteringAppl. Phys. A (2002) accepted

Cavadini, N.; Rüegg, Ch.; Furrer, A.; Güdel, H.U.;Krämer, K.; Mutka, H.; Vorderwisch, P.:Triplet excitations in low-Hc spin gap systemsKCuCl3 and TlCuCl3 – an inelastic neutron scat-tering studyPhys. Rev. B 65 (2002) 132415

Charalambopoulou, G.Ch.; Steriotis, Th.A. Hauß,Th.; Stephanopoulos, K.L.; Stubos, A.K.:A neutron diffraction study of the effect of hydra-tion on stratum corneum structureAppl. Phys. A (2002) accepted

Chatterji, T.; Schneider, R.; Hoffmann, J.-U.; Hohl-wein, D.; Suryanarayanan, R.; Dhalenne, G.;Recolevschi, A.:Diffuse magnetic scattering above TC in quasi-two-dimensional La1.2Sr1.8Mn2O7

Phys. Rev. B, accepted

Chernyavsky, O.; Prokes, K.; Sechovsky, V.; Doerr,M.; Rotter, M.; Loewenhaupt, M.:Thermal-expansion and magnetostriction studyof UNiAl single crystalsCzech. J. Phys. 52 (2002) in print

Coldea, R.; Tennant, D.A.; Habicht, K., Smeibidl, P.;Tylczynski, Z.:Full ferromagnetic saturation of a 2D quantumantiferromagnetAppl. Phys. A (2002) accepted

Coldea, R.; Tennant, D.A.; Habicht, K.; Smeibidl, P.;Wolters, C.; Tylczynski, Z.:Direct measurement of spin hamiltonian andobservation of condensation of magnons in the2D frustrated Quantum Cs2CuCl4Phys. Rev. Letters 88 (13) (2002) 137203

Danilkin, S.; Delafosse, D.; Fuess, H.; Gavriljuk, V.;Ivanov, A.; Magnin, T.; Wipf, H.: Hydrogen vibrations in austenitic stainless steelAppl. Phys. A (2002) accepted



247

Dante, S.; Dencher, N.A.; Hauß, T.:b-amyloid pepdide 25-35 intercalates in anioniclipid membranes as detected by neutron diffrac-tion.Biophysical J., (2001) submitted

Davies, S.M.A.; Harroun, T.H.; Darkes, M.J.M.;Hauss, T.; Cornell, R.B.; Bradshaw, J.P.:A neutron study of lipid sensing by the mem-brane binding domain of phosphocholine cyti-dylyltransferase,Biochemichal Society Transaction (2001) in press

Desmedt, A.; Guillaume, F.; Soetens, J.C.;Dianoux, A.J.; Lechner, R.E.:A combined MD-IQNS investigation of the guestmolecules rotational disorder in thiourea inclu-sion compoundsAppl. Phys. A (2002) accepted

Ehlers, G.; Casalta, H.; Lechner, R. E.; Maletta, H.:Dynamics of frustrated magnetic moments inTbNiAl.Appl. Phys. A (2002) accepted

Ehlers, G.; Ritter, C.; Schneider, R.; Knorr, K.; Ma-letta, H.:Pressure-induced change of magnetic order inTb(1-x)Y(x)NiAl and TbNi(1-x)Cu(x)AlAppl. Phys. A (2002)

Fernández, R.; Bruno, G.; Borrego, A.; González-Doncel, G.; Pyzalla, A.:Determination of residual stresses in 6061Al-15%SiCw composites with different whiskerorientation/distributionAppl. Phys. A (2002) accepted

Feyerherm, R.; Loose, A.; Lawandy, M. A.; Li, J.:Structural and magnetic ordering in the two-dimensional coordination polymerCo(ox)(bpy-d8), (ox = C2O4

2-,bpy-d8 = 4,4’-bipyridine-d8)J. Phys. Chem. Solids 63 (2002) 71-77

Feyerherm, R.; Loose, A.; Lawandy, M. A.; Li, J.:Crystal and magnetic structure of the two-dimensional coordination polymersCoCl2(bpy-d8) and NiCl2(bpy-d8)(bpy-d8 = 4,4’-bipyridine-d8)Appl. Phys. A (2002) in press

Fritzsche, H.; Temst, K.; van Bael, M.J.:Off-specular polarized neutron reflectometryfrom a periodic array of Co-disksAppl. Phys. A (2002) accepted

Gierlings, M.; Prandolini, M.J.; Fritzsche, H.;Gruyters, M.; Riegel, D.:Observation of magnetization rotation duringthe reversal in Co/CoO exchange bias multilay-ersAppl. Phys. A, accepted

Gierlings, M.; Prandolini, M.J.; Fritzsche, H.;Gruyters, M.; Riegel, D.:Change and asymmetry of magnetization rever-sal for a Co/CoO exchange bias systemPhysical Review B (2002) accepted

Gierlings, M.; Prandolini, M.J.; Gruyters, M.; Riegel,D.; Brewer, W.D.:On the possibility of detecting asymmetric ma-gnetization reversal processes in exchange biassystems by low temperature nuclear orientationJ. Magn. Magn. Mat. (2002) accepted

Gilles, R.; Muk herji, D .; Strun z, P.; B arb ie r, B.;Tö bb ens , D .; Ro esler, J .:Co mp aring diffe ren t diffra ction te ch niq ues for the me as ure ment o f g /g `lattic e m is fit in a Re -rich Ni-ba se su peralloy sAp pl. Ph ys . A (20 02) su bmitte d

Glavatska, N.; Mogilniy, G.; Glavatskiy, I.; Danilkin,S.; Hohlwein, D.; Söderberg, O.; Lindroos, V.K. ,Beskrovnij, A.:Temperature dependence of martensite struc-ture and its effect on magnetic filed inducedstrain in Ni2MnGa shape memory alloysProc. ICOMAT-2002, Helsinki, 12-14.June 2002(Journ. de Physique)

Glavatska, N.; Mogilniy, G.; Glavatskiy, I.; Danilkin,S.; Hohlwein, D.:Crystal Strucutre and temperature dependenceof lattice paramaters in martensite of Ni2MnGaalloy studied with neutron diffraction and itseffect on magnetic field induced strainActa Materialia (2002) submitted

Gondek, L.; Subham Majumdar, Sampathkumaran,E.V.; Penc, B.; Stüsser, N.: Szytula, A.:Neutron diffraction study of the crystal and ma-gnetic structure of Ce2Co1-xAuxSi3 (x=0.4, 0.6 and0.8) compoundsJ. Magn. Magn. Mat., in press

Gutberlet, T.; Hoell, A.; Kammel, M.; Frank, J.;Katsaras, J.:Neutron scattering from magnetically alignedbiomimetic substratesAppl. Phys. A (2002) accepted

Gutberlet, T.; Steitz, R.; Howse, J.; Estrela-Lopis, I.;Klösgen, B.:Hybrid biomembrane substructure determinati-on by contrats variation analysisAppl. Phys. A , accepted

Hauschild, J.; Fritzsche, H.; Bonn, S.; Liu, Y.:Determination of the temperature dependence ofthe coercivity in Fe/Cr(110)-multilayersAppl. Phys. A, accepted

Häußler, F.; Palzer, S.; Eckart, A.; Hoell, A.:



248

Microstructural SANS - Studies on HydratingTricalcium Silicate (C3S)Appl. Phys. A

Hernandez-Velasco, J.; Saez-Puche, R.; Hoser, A.;Rodriguez-Carvajal, J.:Low temperature incommensurate magneticorder in R2BaCoO5 (R=rare earth)Appl. Phys. A (2002) in press

Hoell, A.; Müller, R.; Wiedenmann, A.; Gawalek, W.:Core-shell and magnetic structure of Bariumhe-xaferrite fluids studied by SANSJ. Magn. Magn. Mat. (2002) in print

Hoelzel, M.; Danilkin, S.; Hoser, A.; Ehrenberg, H.;Wieder, T.; Fuess, H.: Phonon dispersion in austenitic stainless steelFe-18Cr-12Ni-2MoJ. Appl. Phys. A, accepted

Hofmann, M.; Campbell, S.J. Edge, A.V.J.:Valence and magnetic transitions inYbMn2Si2-xGex

Appl. Phys. A, accepted

Hofmann, M.; Campbell, S.J.; Kaczmarek, W.A.:Mechanochemical Treatment of a-Fe2O3- Micro-structural AnalysisAppl. Physics A (2002) accepted

Hofmann, M.; Campbell, S.J.; Knorr, K.; Hull, S.;Ksenofontov, V.:Pressure-Induced Magnetic Transitions inLaMn2Si2Appl. Phys. A (2002)

Hohlwein, D.:Magnetic interactions and Onsager reaction fieldfrom paramagnetic diffuse neutron scatteringAppl. Phys. A (2002) accepted

Hoinkis, E.; Ziehl, M.:In situ small angle neutron scattering study of 2-propanol adsorption in activated carbon fibersEurocarbon 2000, July 9-13 2000, Berlin, Germany(abstract) to be published in 2002 (Carbon)

Howse, J.R.; Manzanares-Papayanopolous, E., Mc-Lure, I.A.; Bowers, J.; Steitz, R.; Findenegg, G.H.:Cricitcal adsorption and boundary layer struc-ture of 2-butoxyethanol + D2O mixtures at ahydrophyilic silica surfaceJ. of Chemical Physics (2002) accepted

Janousová, B.; Svoboda, P.; Sechovsky, V.; Pro-kes, K.; Nakotte, H.; Ouladdiaf, B.; Císarová, I.:Neutron diffraction study of CePtSnAppl. Phys. A: Material Science & Processing(2002) in print

Kammel, M.; Wiedenmann, A.; Hoell, A.:

Nuclear and magnetic nanostructure of magneti-te-ferrofluids studied by SANSPOLJ. Magn. Magn. Mat. (2002) in print

Keiderling, U.:The new "BerSANS-PC" software for reductionand treatment of small angle neutron scatteringdataAppl.Phys. A , accepted

Keller, T.; Rekveldt, M.T.; Habicht, K.:Neutron larmor diffration measurement of thelattice spacing spread of pyrolytic graphiteAppl. Phys. A (2002) accepted

Kikkinides, E. S.; Stefanopoulos, K. L.; Steriotis, Th.A.; Mitropoulos, A. Ch.; Kanellopoulos, N. K.;Treimer, W.:Combination of SANS and 3D stochastic recon-struction techniques for the study of equilibriumand dynamic properties of nanostructured mate-rialsAppl. Phys. A (2002)

Kiselev, M.A.; Janich, M.; Lesieur, P.; Hoell, A.;Oberdisse, J.; Pepy, J.; Kisselev, A.M.: Gapienko, I.V.;Gutberlet, T.; Aksenov, V.L.:DMPC vesicles and mixed DMPC/C12E8 micellesorientation in strong magnetic fieldsAppl. Phys. A. (2002) accepted

Kolenda, M.; Hofmann, M.; Leciejewicz, J.; Penc,B.; Szytula, A.:Neutron diffraction studies ofR5Rh4Ge10 (R=Tb,Ho,Er) compoundsAppl. Phys. A (2002) accepted

Kranold, R.; Kammel, M.; Hoell, A.:Effect of water on the phase separation charac-teristics of a soda-lime-silica glassPhys. Chem. Glasses (2002) in print

Krimmel, A.; Reehuis, M.; Loidl, A.:CF-effects and disorder versus Kondo latticebehavior in CeTSi3 (T=Rh, Ir)Appl. Phys. A, accepted

Krist, Th.; Fritzsche, H.; Mezei, F.:Large angle neutron polarisation analyserAppl. Phys. A, (2001) accepted

Kunnen, E; Mangin, S.; Moshchalkov, V.V.; Bruyn-seraede, Y.; Vantomme, A.;. Hoser, A.; Temst, K.:Influence of strain on the antiferromagneticordering in epitaxial Cr films on MgOThin Solid Films (2001) accepted

Lake, B.; Roennow, H.M.; Christensen, N.B.; Aeppli,G.; Lefmann, K.; McMorrow, D.F.; Vorderwisch, P.;Smeibidl, P.; Mangkorntong, N.; Sagawa, T.; No-hara, M.; Tagaki, H.; Mason, T.E.:Field-induced antiferromagnetism in a high-temperature superconductor



249

Nature 415 (2002) 299-302

Lebedev, V.T; Török ,Gy.; Cser, L.; Kali,Gy.;Sibilev, A.I.:Molecular dynamics of poly(N-vinylcaprolactam)hydrateAppl. Phys. A (2002) submitted

Lechner, R.E.:Quasielastic high-resolution direct geometryTOF spectrometers at steady-state reactors andat spallation sourcesAppl. Phys. A (2002) accepted

Lo Celso, F.; Triolo, A.; Bronstein, L.; Zwanziger, J.;Strunz, P.; Lin, J.S.; Crapanzano, L.; Triolo, R.:Investigating self-assembly and metal nanoclu-sters in aqueous Di-block copolymers solutionsAppl. Phys. A (2002) accepted

Lo Celso, F.; Triolo, A.; Negroni, F.; Hainbuchner,M.; Baron, M.; Strunz, P.; Rauch, H.; Triolo, R.:Structural investigation on hybrid nanocomposi-tesAppl. Phys. A (2002) accepted

Lo nk ai, T.; Hoh lwe in , D .; Ih rin ger, J.; Pran dl, W.:Th e mag netic struc tu res of Y MnO 3-d an d HoM nO3

Ap pl. P hys . A (200 1) in pres s

Mastoraki, I.; Lappas, A.; Schneider, R.; Giapintza-kis, J.:Spin-gap and antiferromagnetic correlations inlow-dimensional PbNi2-xAxV2O8 compounds(A= Mg, Co)Appl. Phys. A (2002) accepted

Matas, S.; Batko, I.; Boyko, V.; Radulov, I.; Schöttl,S.; Siemensmeyer, K.; Raasch, S.; Sherline, T.E.;Adams, E. D.:Instrument for a neutron scattering experimenton solid 3HeAppl. Phys. A , accepted

Mergia, K.; Baszewski, L. T.; Messoloras, S.;Hamada, S.; Shinjo, T.; Gamari-Seale, H.;Hauschild, J.:Polarized neutron reflectivity study of a Gd/CrmulitlayerAppl. Phys. A (2002) accepted

Mihalik, M.; Matas, S.; Zentkova, M.; Arnold, Z.;Mikulina, O.; Rogl, P.:Investigation of the magnetic phase transition inU3Al2Si3Czechoslovak Journal of Physics, accepted

Moshopoulou, E. G.; Prokes, K.; Garcia-Matres, E.;Pagliuso, P. G.; Sarrao, J. L.; Thompson, J. D.:Neutron diffraction study of field-induced transi-tions in the heavy fermion compound Ce2RhIn8

Physica B (2002) accepted

Mukherji, D.; Strunz, P.; Gilles, R.; Rösler, J.;Wiedenmann, A.; Fueß, H.:In situ SANS investigation of precipitatemicrostructure at elevated temperatures in Re-rich Ni-base superalloyAppl.Phys. A , accepted

Müller, R.; Hiergeist, R.; Gawalek, W.; Hoell, A.;Wiedenmann, A.:Magnetic and structural investigations on bari-um hexaferrite ferrofluidsJ. Magn. Magn. Mat. (2002) in print

Neov, S.; Dabrowski, L.; Hofmann, M.; Bouwmee-ster, H.:Neutron Diffraction and Mössbauer Spectrosco-py Study ofLa0.6Sr0.4Fe1-xCoxO3-y (x = 0, 0.5) PerovskitesAppl. Phys. A (2002) accepted

Neov, S.; Marinova, V.; Reehuis, M.; Sonntag, R.:Neutron diffraction study of Bi12MO20 singlecrystals with sillenite structure(M = Si, Si0.995Mn0.005, Bi0.53Mn0.47)Appl. Phys. A (2002) accepted

Nirmala, R.; Morozkin, A.V.; Hofmann, M.; Sankra-harayanan, V.; Sethupathi, K.; Yamamoto, Y.; Hori,H.:Magnetic Structure of Tb2Mn3Si5J. Alloy Comp. (2002) accepted

Ono, M.; Habicht, K.; Keller, T.:Neutron larmor diffraction measurement of thestrain in the ductile composite Al2O3/Y2Al5O12

(YAG)Appl. Phys. A (2002) accepted

Padureanu, I.; Lechner, R.E.; Aranghel, D.; Radu-lescu, A.; Desmed, A.; Pieper, J.; Ion, M.:Temperature dependence of the dynamic scat-tering function in glycerol studied by quasi-elastic slow neutron scatteringAppl. Phys. A (2002) accepted

Peters, J.; Treimer, W.: On the influence of external forces on the Blochwall thickness in a nickel single crystalJ. Magn. Magn. Mat. 241 (2002) 240-248

Petrenko, O.A.; Balakrishnan, G.; McK Paul, D.;Yethiraj, M.; Klenke, J.:Field induced transitions in the highly frustratedmagnet Gadolinium Gallium Garnet - long orshort range order?Appl. Phys. A. Material Science & Processing(2002) accepted

Pieper, J.; Irrgang, K.-D.; Renger, G.; Lechner,R.E.: Density of phonon states in the light-harvestingcomplex II of green plantsAppl. Phys. A (2002) accepted



250

Pirogov, A.; Park, J.; Jo, Y.; Park, J.-G.; Proke_, K.;Welzel, S.; Lee, C.H.; Kudrevatykh, N.; Valiev, E.;Kazantsev, V.; Sheptyakov, D.:Magnetization and magnetic anisotropy of Tm-and Fe-subsystems in Tm2Fe17

Journal Phys. of Metals and Metallografy (2002) inpress

Prokes, K.:Neutron Scattering on Magnetic Materials underExtreme ConditionsCzech. J. Phys. 52 (2002) in print

Prokes, K.; Javorsky, P.; Gukasov, A.; Brück, E.;Sechovsky, V.:Field-induced change of the antiferromagneticstructure of UNiAlPhysica B: Condensed Matter (2002) in press

Prokes, K.; Tahara, T.V.; Echizen, Y.; Takabatake,T.; Fujita, T.; Hagmusa, I.H.; Klaasse, J.C.P.; Brück,E.; de Boer, F.R.; Divis, M.; Sechovsky, V.:Electronic properties of a URhGe single crystalPhysica B: Condensed Matter (2002) in press

Prokes, K.; Tegus, O.; Brück, E.; Klaasse, J.C.P.;de Boer, F.R.; Buschow, K.H.J.:Magnetic properties and magnetic structure ofHoTiGe and ErTiGeJ. of Alloys and Compounds (2002) in press

Prokes, K.; Nakotte, H.; Brück, E.; de Châtel, P.F.;Sechovsky, V.:Field-induced magnetic structures in UNiGeAppl. Phys. A: Material Science & Processing(2002) in print

Przenioslo, R.; Regulski, M.; Sosnowska, I.;Schneider, R.:Modulated magnetic ordering in the Cu-dopedpseudoperovsike system CaCuxMn3-xMn4O12

J. Phys. Condens. Matter 14 (2002)1061-6

Radulescu, A.; Lechner, R. E.; Padureanu, I.;Postolache, C.:Additional low- frequency modes in zirconiumhydridesAppl. Phys. A (2002) accepted

Rekveldt, M.Th.; Kraan, W.H.; Keller, T.:High resolution diffraction using Larmor pre-cession of polarised neutronsJ. of Applied Cryst. 23/3/2001 (submitted)

Rogalski, O.; Vorderwisch, P.; Hüller, A.; Hautecler,S.:A heuristic quantum dissipation algorithm ap-plied to new neutron scattering data of the freeammonia rotations in the Ni-Ni-biphenylHofmann clathrateJ. Chem. Phys. (accepted)

Rousseau, D.; Marty, J.-D.; Mauzac, M.; Martinoty,P.; Brandt, A.; Guenet, J.-M.:Conformation of o side-chain liquid crystal po-lymer in solutionAppl. Phys. A (2002)

Rüegg, Ch.; Cavadini, N.; Furrer, A.; Kräemer, K.;Güdel, H.U.; Vorderwisch, P.; Mutka, H.:Spin dynamics in the high field phase of quan-tum critical S=1/2 TlCuCl3Appl. Phys. A (accepted)

Russina, O.; Russina ,M.; Mezei, F.; Lechner, R.E.;Pieper, J.; Desmedt, A.:Dynamic correlations around the glass transiti-on in systems with different degrees of fragilityAppl. Phys. A (2002) accepted

Schöttl, S.; Siemensmeyer, K.; Boyko, V.; Batko, I.;Matas, S.; Raasch, S.; Adams, E. D.; Sherline, T.E.:Neutron scattering experiment on solid 3HeJ. of Low Temperature Physics 126 (2002) 51-56

Schuck, G.; Lechner, R. E.; Langer, K.:Proton conduction based on intracrystallinechemical reactionAppl. Phys. A (2002) accepted

Sechovsky, V.; Andreev, A. V.; Syshchenko, O.;Prokes, K.; Bartachevich, M.I.; Goto, T.:On the treshold of long-range magnetic order:UNi2/3Rh1/3Al and UCoAl studyCzech. J. Phys. 52 (2002) in print

Sechovsky, V.; Prokes, K.; Honda, F.; Khmelevski,S.; Ouladdiaf, B.; Kulda, J.:Pressure-induced magnetic structures in UNiGaAppl. Phys.A: Material Science & Processing (2002)in print

Sitepu, H.; Schmahl, W.W.; Eggeler, G.; Khalil Allafi,J.; Többens, D.M.:An in-situ neutron diffraction study of the mar-tensitic transformation in aged Ni-rich NiTi al-loysJournal de Physique IV (2002) submitted

Sitepu, H.; Schmahl, W.W.; Khalil Allafi, J.; Eggeler,G.; Dlouhy, A.; Tobbens, D.M.; Tovar, M.:Neutron diffraction phase analysis during ther-mal cycling of a Ni-rich NiTi shape memory us-ing the Rietveld methodScripta Materialia (2002) in print

Sitepu, H.; Schmahl, W.W.; Khalil Allafi, J.; Eggeler,G.; Reinecke, T.; Brockmeier, H.G.; Tovar, M.; Töb-bens, D.M.:A quantitative analysis of martensitic phasesand their crystallographic texture in an aged Ni-rich NiTi alloy using x-ray and neutron diffrac-tion dataMaterials Science Forum (2002) in print



251

Sittner, P.; Lukás, P.; Neov, D.; Daymond, M.R.;Novák, V.; Swallowe, G.M.:Stress induced martensitic transformation inCuAlZnMn polycrystal investigated by two insitu neutron diffraction techniquesMat. Sci. Eng. A 324 (2002) 225-234

Steriotis, Th. A.; Stefanopoulos, K. L.;, Mitropoulos,A. Ch.; Kanellopoulos, N. K.; Hoser, A.; Hofmann,M.:Structural studies of supercritical CO2 in confi-ned spaceAppl. Phys. A (2002) accepted

Strunz, P.; Schumacher, G.; Chen, W.; Mukherji, D.;Gilles, D.; Wiedenmann, A.:SANS examination of precipitate microstructurein creep-exposed single-crystal Ni-base su-peralloy SC16Appl. Phys. A, accepted

Stüßer, N.; Hofmann, M.:An adjustable in-pile fan collimator for focusingin a neutron diffractometerNuclear Instruments and Methods, in: Physics Re-search (2002) accepted

Svoboda, P.; Vejpravova, J.; Rotter, M.; Doerr, M.;Loewenhaupt, M.; Hofmann, M.; Schneider, R.:Complex magnetic phase diagram of TmCu2

Appl. Phys. A, accepted

Syshchenko, O.; Prokes, K.; Brück, E.; Sechovsky,V.:Magnetic field induced irreversibility in specificheat of UNiAlPhysica B: Condensed Matter (2002) in press

Syshchenko, O.; Prokes, K.; Sechovsky, V.; Fujita,T.; Suzuki, T.:Magnetic-history dependent magnetoresistancein UNiAlPhysica B: Condensed Matter (2002) in press

Syshchenko, O.; Prokes, K.; Sechovsky, V.; Sato,H.; Kobayashi, Y.:Magnetic-history effects in Hall resistivity ofUNiAlCzech. J. Phys. 52 (2002) in print

Szytula, A.; Penc, B.; Stüsser, N.:Neutron diffraction studies of magnetic structu-res of ErRu2Ge2

J. Magn. Magn. Mat. 238 (2002) 65-67

Szytula, A.; Penc, B.; Stüsser, N.; Œlaski, M.:Magnetic phase transitions in ErRhSiJ. Magn. Magn. Mat., in press

Szytula, A.; Bazela, W.; Gondek, L.; Jaworska-Gotab, T.; Penc, B.; Stüsser, N.; Zygmunt, A.:Neutron diffraction and magnetisation studies ofmagnetic ordering in RAuIn (R=Tb,Dy,Ho)

J. of Alloys and Compounds 1 (2001) in press

Temst, K.; van Bael, M.J.; Fritzsche, H.:Off-specular polarized neutron reflectometrystudy of magnetic doits with a strong shapeanisotropyAppl. Phys. A (2002) accepted

Tomuta, D. G.; Nieuwenhuys, G. J.; Feyerherm, R.;Mydosh, J. A.:Magnetic alignment of the RE sublattice in ReM-nO3

Appl. Phys. A (2002) accepted

Treimer, W.; Strobl, M.; Hilger, A.:Thermal neutron optical experiments with a highresolution double crystal diffractometerAppl. Phys. A (accepted)

Treimer, W.; Strobl, M;, Hilger, A.:Evidence of edge diffraction and refraction inultra small angle neutron scatteringPhys. Rev. Lett., submitted

Triolo, A.; Lechner, R.E.; Desmedt, A.; Telling, M.;Arrighi, V.:Complex dynamics in polyisobutylene meltsMacromolecules (2002) submitted

Triolo, A.; Lo Celso, F.; Negroni, F.; Arrighi, V.;Qian, H.; Lechner, R.E.; Desmedt, A.; Pieper, J.;Frick, B.;Triolo, R.:QENS Investigation of filled rubbersAppl. Phys. A (2002) accepted

Triolo A.; Lo Celso F.; Passerini, S.; Arrighi V.;Lechner R.E.; Frick B.;Triolo R.:Segmental dynamics in polymer electrolytesAppl. Phys. A (2002) accepted

Triolo, A.; Lo Celso, F.; Arrighi, V.; Strunz, P.;Lechner, R.E. Mastragostino, M.; Passerini, S.;Annis, B.K.; Triolo, R.:Structural and dynamical characterization ofmelt PEO-salt mixturesPhysica A 304 (2002) 308

Troyanov, S.I.; Zakharov, M.A.; Reehuis, M.; E.Kemnitz, E.:Neutron diffraction study of sodium hydrogenselenate Na3H5(SeO4)4. Comparison with X-raydiffraction dataCrystallography Reports 47 (2002) 29

Ulbricht, A.; Böhmert, J.; Strunz, P.; Dewhurst, C.;Mathon, M.-H.:Microstructural investigations on russian reac-tor pressure vessel steels by small angle neu-tron scatteringAppl. Phys. A, accepted



252

Ulrich, C.; Khaliullin, G.; He, H.; Reehuis, M. Ohl,M.; Ivanov, A.; Taguchi, Y.; Tokura,Y.; Keimer, B.:Spin order and orbital degrees of freedom inYVO3 and LaVO3

Appl. Phys. A (2002) accepted

Ulrich, C.; Kondo, S.; Reehuis, M.; He, H.; Bern-hard, C.; Bouree, F.; Bourges, P.; Ohl, M.; Ronnow,H.M.; Tagaki, H.; Keimer, B.:Structural and magnetic instabilities of La2-

xSrxCaCu2O6

Phys. Rev. Lett. (2002) submitted

v. Klitzing, R.; Kolaric, B.; Jaeger, W.; Brandt, A.:Structuring of poly (DADMAC) chains in aqueousmedia: A comparison between bulk and freestand-ing film measurementPCCP, accepted

v. Klitzing, R.; Steitz, R.:Internal structure of polyelectrolyte multilayersin: Handbook of Polyelectrolyte, eds.: S.K. Triphaty,H.S. Nalwa, American Scientific Publishers, invitedReview article, accepted

Wiedenmann, A.; Hoell, A.; Kammel, M.:Small-angle scattering investigations of Cobalt-Ferrofluids using polarized neutronsJ. Magn. Magn. Mat. (2002) in print

Zrník, J.; Strunz, P.; Hornák, P.; Vrchovinsky, V.;Wiedenmann, A.:Microstructural changes in long-time thermallyexposed Ni-base superalloy studied by SANSAppl. Phys. A, accepted


Seminars and Conference Contributions 2001

253

Invited Talks

2000 (supplement)

Rakecha, V.C.; Wagh, A.:Observing SU (2) phases with neutronsInt. Conf. „Foundations of Quantum Theory“, Jan.2000

2001

Baglioni, P.; Baldelli Bombelli, F.; Berti, D.; Keiderling,U.:Living polynucleotides formed by thespontaneous aggregation ofdilauroylphospholiponucleosidesICNS 2001, Munich, Germany, September 9-13, 2001

Bouwman, W.G.:Spin-echo small-angle neutron scatteringIU-LENS Workshop, Bloomington, USA, Nov. 17,2001

Broholm, C.:Magnets without directionColloquium, Department of Physics, GeorgetownUniversity, Washington, DC USA, Sept. 27, 2001

Broholm, C.:Magnets without directionColloquium, Department of Physics and Astronomy,Rutgers University, New Jersey, USA, Oct. 17, 2001

Broholm, C.:Quantum phase transition in a quasi-two-dimensional frustrated magnetYale University, Connecticut, USA, Nov. 29, 2001

Broholm, C.:Quantum phase transition in a quasi-two-dimensional frustrated magnetFlorida State University, Florida, USA , Dec. 14, 2001

Cavadini, N.; Rüegg, Ch.; Furrer, A.; Güdel, H.U.;Krämer, K.; Mutka, H.; Wildes, A.; Habicht, K.;Vorderwisch, P.:Studies around the simple behaviour of simplesystems: spin excitations in selected(quantum)antiferromagnets1. PSI-Risø Workshop Villigen, Switzerland,November 16-17, 2001

Davies, S.M.A.; Hauß, T.:Regulation of intracellular proteins by membranebinding: don’t forget the lipids!Membrane Biology Group, Department of BiomedicalSciences, University of Edinburgh, Edinburgh, U.K.August 29th 2001

Desmedt, A.; Guillaume, F.; Soetens, J.C.; Dianoux,A.J.; Lechner, R.E.:

Molecular dynamics and phase transitions incyclohexane/thiourea andchlorocyclohexane/thiourea intergrowth crystals8th Int. Seminar on Neutron Scattering Investigation inCondensed Matter, Poznan, May 10-12, 2001

Desmedt, A.; Kitchin, S.J.; Guillaume, F.; Couzi, M.;Harris, K.D.M.; Lechner, R.E.:A multi-technique approach for elucidating thephase transition mechanisms in organicnanoporous materials20th European Crystallographic Meeting:Crystallography and complementary techniques,Krakow, August 25-31, 2001

Ehlers, G.; Casalta, H.; Lechner, R.; Maletta, H.:Dynamics of frustrated magnetic moments inTbNiAlICNS 2001, Munich, Germany, September 9-13, 2001

Feyerherm, R.:Magnetismus in molekularen MaterialienSeminar an der TU Braunschweig, 18. 05. 2001

Fritzsche, H.; Lieutenant, K.:Moderator requirements for reflectometry at apulsed neutron sourceWorkshop on Moderator concepts and optimizationfor spallation neutron sources, HMI Berlin, March 13,2001

Fritzsche, H.; Lieutenant, K.:MC simulations of reflectometers at reactor andspallation sources7th ESS General Meeting, Seggau, Austria,September 26-29, 2001

Fritzsche, H.; Temst, K.; van Bael, M.J.; Mangin, S.:Polarized neutron reflectometry from magneticlayers, multilayers and periodically structuredsamplesSeminar of the Laboratoire de physique desmatériaux, Université Henri Poincaré, Nancy, France,June 27, 2001

Ge nz el, Ch .:Mö glich keite n u nd Pe rsp ektiv en derEige nsp ann un gs- un d Mik ros truktura na lytik mitSy nc hro tro ns tra hlu ng Wo rk sho p „Re sea rch w ith Sy nc hro tro n Rad iatio n“ derFrie drich-Alexa nde r Universität Erla nge n-N ürnbe rg,Erla nge n, 19 .07 .-2 0.07.200 1

Ge nz el, Ch .:Diffrac tio n stress -g rad ien t ana lys is from su rfa ce to vo lu meSE IF ERT -Sy mp osion „X -Ra y-D iffra ction an d N ew Fields of In dus trial Ap plica tio n“, P rag ue, C zec hRe pu blic, 23 .10 .-2 4.10.200 1

Ge nz el, Ch .:Prob lem s relate d to X-ray stres s a na lys is in th infilm s in p re sen ce of gradien ts and texture



254

Size Strain III, T re nto , Ita lie n, 02 .12 .-0 5.12.200 1

Gutberlet, T.:X-ray and neutron reflectivity: a tool to investigatephospholioid bilayer and protein structures atinterfacesIMEC, Leuven, Belgium, Feb. 22, 2001

Gutberlet, T.:Simulations of SANS instruments for ESSWorkshop on VITESS 2.0 and other Packages forSimulations of Neutron Scattering, HMI, Berlin, June25-27, 2001

Hauß, T.; Dante, S.; Dencher, N.A.:Does Alzheimer’s b -amyloid act inside the cellmembrane? A neutron diffraction study4th Workshop on Functional Materials, Geestacht,April 4 - 5, 2001

Häußler, F.:Neutronenkleinwinkelstreuung - Ein Beitrag zurmikrostrukturellen Aufklärung deshydratisierenden ZementsteinsBaustoff-Kolloquium, F.A. Finger-Institut fürBaustoffkunde der Bauhaus-Universität Weimar,06.04.2001

Häußler, F.:Neutronenkleinwinkelstreuung (SANS) zurmikrostrukturellen Aufklärung deshydratisierenden Zementsteins (invited talk),Bauchemisches Kolloquium, Lehrstuhl für Bauchemie(Prof. J. Plank) an der TU München, Garching,23.05.2001

Häußler, F.:Von der Mikro- zur Makrostrukturzementgebundener Betone – AusgewählteUntersuchungen am Institut für Massivbau undBaustofftechnologie LeipzigInstitut für Gesteinshüttenkunde an derMontanuniversität Leoben (Austria), 18.10.2001

Heinemann, A.; Hermann, H.; Wiedenmann, A.;Mattern, N.; Kühn, U.; Bauer, H.-D.; Eckert, J.:Insight into the formation of ultrafinenanostructures in bulk anmorphous Zr Ti-AlCuNiTMR, Boston, USA, 01.12.2001

Hoell, A.:Untersuchung magnetischer Nanostrukturenmittels Neutronen-KleinwinkelstreuungTU Bergakademie Freiberg, Germany, 17.5.2001

Hoell, A.:Small angle scattering using neutrons or X-raysas complementary methodsIoP Wales (Institut of Physics Wales), Aberystwyth,Wales, 01.11.2001 (colloquium)

Jauch, W.:

Benefits from the use of gamma radiation incharge density studiesGordon Research Conference ‘Electron distributionand chemical bonding‘, Mount Holyoke College,South Hadley (MA) USA, July 8-13 2001

Keiderling, U.; Seydel, J.; Winterer, M.; Benker, A.;Wiedenmann, A.; Hahn, H.:Structural development of nanocrystalline Y2O3-doped ZrO2 ceramics investigated with sans usingcontrast variation and in-situ measurementtechniquesUniversity of Florence, Italy, 18.06.2001

Köbler, U.:The impact of fourth-order exchange interactionson spin dynamics, order parameters and criticalbehaviourUniversity of Prag, May 7, 2001

Köbler, U.:Experimentelle Fakten gegen die Gültigkeit derBloch-Kubo-Dyson SpinwellentheorieUniversität Karlsruhe, May 14, 2001

Kolaric, B.; Toca, J.; Jaeger, W.; v. Klitzing, R.:Structuring of Poly(DADMAC) chains in aqueousmedia: A comparison between bulk andmeasurementsHahn–Meitner–Institut (Soft-condensed matterseminar), Berlin, 12.3.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Strukturierung von Polyelektrolyten in dünnenFilmen und an GrenzflächenTU München (W. Petry) Physik Dept. E 13, 4.10.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Polyelektrolyte und Diblock-copolymere indünnen FilmenUniv. Bayreuth Sfb-Kolloquium, 17.12.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Interactions between polyelectrolytes andsurfactants in free-standing blacksTagung der Deutschen Physikalischen Gesellschaft,Berlin, 2.4. – 6.4.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Structuring of polyelectrolyte chains in thin free-standing and in bulk solutionsInstitut Charles Sadron, Strasbourg, 3.7.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Ordnung kationischer Polyelektrolyte zwischenzwei flüssigen GrenzflächenTU Chemnitz, Institut für Physik, 12.7.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Pressure and fluorescence studies on free-standing polymersUniversité Catholique Louvain, Belgien, 30.7.2001



255

Kolaric, B.; Toca, J.; v. Klitzing, R.:Aqueous foam containing amphiphiles andpolyelectrolytesECIS 2001, Coimbra (Portugal), 17.9.–22.9.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Structuring of polyelectrolytes of differentarchitectures in bulk and in freestandingHauptversammlung der Kolloidgesellschaft, Potsdam,24.9.–26.9.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Einfluss von Polyelektrolyten auf die Stabilitätvon freistehenden TensidenKolloquium des Sfb 294, Universität Leipzig,10.1.2001

Kolaric, B.; Toca, J.; v. Klitzing, R.:Strukturierung von PDADMAC-Ketten inverschiedenen GeometrienBerlin-Brandenburgischer Verband vonPolymerforschung e.V. (J. Rabe) 26.10.2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H.; Hussey, N.E.:Magnetic field-induced antiferromagnetism in thehigh-temperature superconductor, La2-xSrxCuO4.Physical Phenomena at High Magnetic Fields IV(PPHMF4 ’01), Santa Fe, NM, U.S.A., October 19-252001

Lechner, R.E.:Observation-time dependent dynamic structurefrom quasielastic neutron scattering8th Int. Seminar on Neutron Scattering Investigation inCondensed Matter, Poznan, May 10-12, 2001

Lechner, R.E.:Mechanismus der Protonenleitung: ElementareSprungprozesse und intrakristallineReaktionsgleichgewichte in festenProtonenleiternKolloquium, Universität Kiel, 17. 5. 2001

Lechner, R.E.:Quasielastic scattering and the EISF: How it allbegan!Colloquium in Honour of José Dianoux, Institut Laue-Langevin Grenoble, France, December 7, 2001

Lieutenant, K.:Introduction to VITESSWorkshop on VITESS 2.0 and Other Packages forSimulations of Neutron Scattering, HMI Berlin,Germany, 25-27 June 2001

Lieutenant, K.:VITESS – Status March 2001Software for Computer Aided Neutron Scattering, EURTD network 2000-2002, general meeting. May 20-21, 2001, PSI, Switzerland

Lieutenant, K.; Zsigmond, G.; Fromme, M.:New features in VITESS 2.1Software for Computer Aided Neutron Scattering, EURTD network 2000-2002, Dobogokö, Hungary,general meeting, October 11-12, 2001

Mezei, F.:Instrumentierung ESS: Hohe IntensitätenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Mezei, F.:Fast heterogeneous relaxation near the glasstransition4th Int. Discussion Meeting on Relaxations in ComplexSystems, Hersonissos, Heraklion, Greece, June 18-26, 2001

Mezei, F.:Instrumentation issues, established techniques,need for innovation, technical risksESS-SAC/ENSA Workshop on "Scientific Trends inCondensed Matter Research and InstrumentationOpportunities at ESS", Jülich, D, 2001

Mezei, F.:Performance of a suite of generic instruments onESSSAC Workshop, Jülich, Germany, 3.-5. May 2001

Mezei, F.:Multiplexing techniques for pulsed neutronsourcesICNS 2001, Munich, Germany, September 9-13, 2001

Mezei, F.:ESS instrumentation studies7th ESS General Meeting, Seggau, Austria,September 26-29, 2001

Mezei, F.:Instrumentation developmentLANSCE User Meeting, Los Alamos, USA, August2001

Mezei, F.:ESS activities at HMIESS Wissenschaftsrat-Audit, FZ Jülich 10-11December 2001

Mezei, F.:Overview of the results of the instrument groups:Performance of key instruments at the differenttarget stations of ESSWorkshop on Scientific Trends in Condensed MatterResearch and Instrumentation Opportunities at ESSEngelberg, Switzerland, 3-5 May 2001

Mezei, F.; Russina, M.:Intermediate range dynamics in supercooledliquids



256

Millenium Symposium, ILL, Grenoble, France, 5-8April 2001

Moshopoulou, E.G.:Diffraction studies of the heavy fermioncompounds CemTnIn3m+2n (T = Co, Rh, Ir; m = 1, 2;n = 1)6th Patras Euroconference on Properties ofcondensed matter probed by x-ray and neutronscattering, September 21 - 25, 2001

Nørgaard Toft, K.; Abrahamsen, A.B.; Andersen,N.H.; Lefmann, L.; Hedegård, P.; Jensen, J.;Eskildsen, M.R.; Canfield, P.C.; Vorderwisch, P.;Meissner, M.; Smeibidl, P.; Kausche, S.:Neutronspredning – Det ultimative værktøj tilbestemmelse af struktur og dynamikAnnual meeting of the Danish Neutron ScatteringSociety, Copenhagen, January 29th 2001

Nørgaard Toft, K.; Abrahamsen, A.B.; Andersen,N.H.; Lefmann, L.; Hedegård, P.; Jensen, J.;Eskildsen, M.R.; Canfield, P.C.; Meissner, M.;Günther, D.; Vorderwisch, P.; Klenke, J.; Prokes, K.;Smeibidl, P.; Kausche, S.:Superconductivity and magnetism in the rareearth nickel borocarbidesBerliner Tieftemperatur-Kolloquium, Berlin, June 12th

2001

Pappas, C.:Introduction to NSE spectroscopyInternational Workshop on New Opportunities inSingle Crystal Spectroscopy with Neutrons, Révfülöp,Hungary, 19-22.4.2001

Pappas, C.:Polarised neutrons in spectroscopy anddiffractionWorkshop on dynamics, excitations and magnetism,ANSTO, Menai, Australia, 27-28.8.2001

Pappas, C.; Mezei, F.; Ehlers, G.; Campbel, I.A.:Relaxation dans les verres de spinJournées de la Diffusion Neutronique JDN10,Trégastel, France, 16-18.5.2001

Prokes, K.:Magnetic neutron scattering under extremeconditionsDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Prokes, K.;Neutron scattering on magnetic materials underextreme conditions11th Czech and Slovak Conference on MagnetismCSMAG’01, Kosice, 22.8. 2001

Pyzalla, A.:Synchrotronstrahlung: Neue Möglichkeiten zurAnalyse der Mikrostruktur, der Textur und derEigenspannungen

Frühjahrstagung der DPG, Hamburg, 26.03.2001

Pyzalla, A.:Fertigung und Betriebsbeanspruchung vonBauteilen: Auswirkungen auf den Werkstoff undseine MikrostrukturKolloquium: Werkstoffeinsatz TU Wien, Wien,18.12.2001

Py za lla , A .:Da s Materialforsch un gsd iffra kto meter Stres s-Spe cSe minar „S pe zie lle P rob lem e der Nu klearenFe stkörperph ysik“, T U M ünc he n, 29.01 .20 01

Py za lla , A .:Beugung mit Synchrotron - undNeutronenstrahlen: Neue Möglichkeiten zurAnalyse der MikrostrukturSeminar des MPI für Eisenforschung Düsseldorf,Düsseldorf, 30.01.2001

Py za lla , A .:Charakterisierung von Texturen undEigenspannungsverteilungen mit Synchrotron-Röntgenstrahlung und NeutronenSeminar „Aktuelle Probleme derWerkstoffwissenschaften“, Universität Nürnberg-Erlangen, Erlangen, 17.05.2001

Pyzalla, A.; Wang, L.; Wild, E.; Wroblewski, T.:Mikrostrukturelle Veränderungen durch denVerschleiß von Schienenoberflächen - Analysenmit Beugungsverfahren -Seminar, Institut für Mechanik A, TU München,24.07.2001

Reimers, W.:Capabilities of neutron and high energy X-rays formaterials scienceICNS 2001, Munich, Germany, September 9-13, 2001

Rekveldt, M.Th.:New instrumentation using larmor precession ofpolarized neutronsIU-LENS Workshop, Bloomington, USA, November17, 2001

Rekveldt, M.Th.:Neutron depolarisation and spin-echo small-angleneutron scatteringNanoscience network UK, Chester (GB) December2001

Rekveldt, M.Th.:Spin-echo small-angle neutron scattering andhigh resolution larmor diffractionDubna, Russland, January 24, 2001 (seminar talk)

Schneider, R.:Investigation of diffuse scattering contributionsarising from magnetic and structural disorder bymeanfield-like theories



257

Europ. Cryst. Meeting ECM20 , Krakow (PL), August25-30, 2001

Schöttl, S.:State of the HMI experiment – the cryogenic partFirst Summer School of EU-RTN Project „NeutronScattering from Solid 3Helium“, 27. – 31.08.2001,Frauenchiemsee

Schöttl, S.:New development of the cryostat3rd meeting of the 3He Neutron study group, 27. –28.04.2001, Grenoble

Schubert-Bischoff, P.; Bloeck, U.:Die “T-tool” Technik: ein einfaches underfolgreiches Verfahren zur Herstellung vonDünnschliffen für die IonenstrahlätzungBAL-TEC Anwendertreffen “Ionenstrahlätzen”,Tübingen (D), May 16-17, 2001

Stone, M.B.:Gapped frustrated quantum magnetsNational Center for Neutron Research Seminar,National Institute of Standards and TechnologyGaithersburg, MD, USA, October 25, 2001

Stone, M.B.:Gapped frustrated quantum magnetsCondensed Matter Seminar, Department of Physics,Johns Hopkins University, Baltimore, MD, USA,October 17, 2001

Strobl, M.; Hilger, A.; Treimer, W.:Slit effects at dynamical diffractionPECNO Meeting, Grenoble, France, 1.-4. April 2001

Strobl, M.; Treimer, W.; Hilger, A.; Wagh, A.:Messungen von NeutronenvielfachreflexionenSeminar für Neutronen- und Festkörperphysik,Atominstitut Wien, 29. 6.2001

Strunz, P.; Saroun, J.:Small-angle neutron scattering studies of sometechnologically important materialsSeminar at TU Braunschweig, Institut für Werkstoffe,27.11.2001

Stüßer, N.; Hoser, A.; Schotte, U.; Meschke, M.;Meißner, M.:Neutron diffraction of fluctuation inducedmagnetic phases of CsCuCl3 in fields up to 17Tesla20th European Crystallographic Meeting, Krakow (PL),August, 25-31, 2001

Temst, K.:Thin film nanostructures studied by magneticforce microscopy and polarized neutronreflectometry16th Workshop on Novel Materials and Supercond.,Donnersbach, Austria, February 2001

Temst, K.:Structural and magnetic properties of mesoscopicferromagnetic islandsMeeting on Quantum Magnetic Dot Systems, Paul-Drude-Institut, Berlin, March 2001

Temst, K.:Toepassing van diffractie en reflectie vanneutronenbundels voor de studie van demagnetische ordening in dunne filmen ennanostructurenTalk at the occasion of the award ceremony of thescientific prize SCK.CEN Prof. Roger E. Van Geen,Mol, Belgium, April 2001

Temst, K.:Magnetic films studied by polarized neutronreflectometry1st Flemish-Hungarian Workshop on Electronicproperties in reduced dimensionalities, Leuven,Belgium, May 2001

Temst, K.:Mesoscopic ferromagnetic islands studied bymagnetic force microscopy and polarized neutronreflectometryIMEC vzw, Leuven, Belgium, September 2001

Temst, K.:Neutron reflectivity study of magnetic islands andinterfacesESF-Nanomag Workshop, Biarritz, France, October2001

Temst, K.:Structural and magnetic properties of periodic dotlattices studied by off-specular x-ray and neutronreflectivitySymposium on Multilayers as seen by photons andneutrons, Budapest, Hungary, December 2001

Treimer, W.; Strobl, M.:Doppelkristalldiffraktometrie und TomographieAnwender - Workshop zur Nutzung derNeutronenradiographie, Paul Scherrer Institut,Villingen (CH) 14. 5. 2001

Treimer, W.; Strobl, M.; Hilger, A.; Seifert, C.:Refraction tomographyCost – Session, Munich, Germany, Sept. 2001

Treimer, W.; Strobl, M.; Hilger, A.; Seifert, C.:Tomography with cold neutronsPECNO meeting, Vienna, Dez. 6-8 2001

Wagh, A.; Rakecha, V. C.; Treimer, W.:First realisation of bonse-hart angular profiles formultiple bragg reflectedICNS 2001, Munich, Germany, September 9-13, 2001

Wiedenmann, A.:Small angle neutron scattering investigations ofnanomaterials



258

"Tables Rondes -Systemes Desordonnes".Laboratoire Leon Brillouin, Saclay, France, 3.12.2001

Wiedenmann, A.:Small angle neutron scattering investigations ofnanomaterialsSeminar at Advanced Materials R&D Centre, Kulim,Malaysia, 29.10.2001Wiedenmann, A.:Strukturuntersuchungen in ferrofluidenDfg Spp1104 Workshop, Benediktbeuren, 3.10.2001

Wiedenmann, A.:Sans investigations in ferrofluids9th Int. Conference On Magnetic Fluids (Icmf9),Bremen, (Germany), 24.7.2001

Wiedenmann, A.:investigations in nanoscaled materialsEgyptian Solid State Association (Essa) Conference,Hurghada, Egypt, 18.3.2001

Wiedenmann, A.:Polarised neutrons for structural research innanoscaled materialsIntense Pulsed Neutron Source IPNS, Argonne,Illinois, USA, 01.07.2001

Wiedenmann, A.:Reactor utilization at HMISeminar on MINT Nuclear Reactor Research , BandarBaru, Malaysia, 27.10.2001

Wiedenmann, A.:Strukturuntersuchungen in FerrofluidenDFG SPP1104 Workshop, Benediktbeuren,03.10.2001

Wiedenmann, A.:SANS investigations in nanoscaled materialsESSA Conference Hurghada, Egypt, 18.03.2001

Wiedenmann, A.:SANS investigations in ferrofluids9TH Int. Conference on Magnetic Fluids (ICMF9)Bremen, Germany, 24.07.2001

Wiedenmann, A.:Small angle neutron scattering investigations ofnanomaterialsWorkshop on Advanced Materials SIREM-AMRECR&D Centre, Kulim, Malaysia, 29.10.2001

Wiedenmann, A.:Small angle neutron scattering investigations ofnanomaterials"Tables Rondes -Systèmes désordonnés".Laboratoire Léon Brillouin, Saclay, France,03.12.2001

Wiedenmann. A.:Investigations of nanomaterials by small angleneutron scattering (SANS) Malaysian Institute of

Nuclear Technology (MINT), Serpong, Malaysia,31.10.2001

Wilmer, D.:Quasielastische Neutronenstreuung zurCharakterisierung spezieller ionenleitenderSystemeDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Zsigmond, G.:New features in VITESS 2.0Workshop on VITESS 2.0 and other Packages forSimulations of Neutron Scattering, HMI Berlin, 25-27June 2001

Zsigmond, G.:Polarisation analysis with VITESS 2.1Software for Computer Aided Neutron Scattering, EURTD network 2000-2002, general meeting,Dobogokö, Hungary, October 11-12, 2001

Other Talks

Bickulova, N.; Danilkin, S.; Fuess, H.; Semenov, V.;Skomorokhov, A.; Wieder, T.; Yadrowski, E.;Yagofarova, Z.:Lattice dynamics and phase transitions insuperionic conductor Cu2-d SeSecond German-Russian User-Meeting “CondensedMatter Physics with Neutrons”, Dubna, April 21-24,2001

Bouchard, P.J.; Fiori, F.; Treimer, W.:Characterisation of creep cavitation damage in apressure vessel stainless steel using small angleneutron scatteringICNS 2001, Munich, Germany, September 9-13, 2001

Bouwman, W.G.:A novel high-resolution neutron diffractiontechnique aplied to recrystallisation phenomenain aluminiumMaterials research 2001, Veldhoven, May 8-9, 2001

Charalambopoulou, G.Ch.; Steriotis, Th.A.;Stefanopoulos, K.L.; Stubos, A.K.; Kanellopoulos,N.K.:Study of the structure of stratum corneum bysmall angle neutron scattering3rd Panhellenic Scientific Conference on ChemicalEngineering, Athens, May 31-June 2, 2001

Coldea, R.; Tennant, D.A.; Habicht, K.; Smeibidl, P.;Tylczynski, Z.:Excitations of a 2D frustrated quantum magnet inthe high- field ferromagnetic phaseICNS 2001, Munich, Germany, September 9-13, 2001

Czihak, C.; Müller, M.; Schober, H.; Seydel, T.; Vogel,G.:



259

Supercooled water in plant cell walls – structureand dynamics of water adsorbed to celluloseICNS 2001, Munich, Germany, September 9-13, 2001

Danilkin, S.; Fuess, H.; Hölzel, M.; Wieder, T.; Hoser,A.; Noeva-Baeva, M.; Beskrovni, A.; Jadrovski, E.:Investigations of the lattice dynamics of transitionmetals and alloys with spectrometer DIN-2PISecond German-Russian User-Meeting “CondensedMatter Physics with Neutrons”, Dubna, April 21-24,2001

Eschricht, N.; Hoinkis, E.; Mädler, F.; Röhl-Kuhn, B.:A SANS study of nitrogen adsorption in themesoporous silica glass Gelsil 50 and thereconstruction of the porous structureFirst Topical Conference on Nanoscale Science andEngineering, Reno(NV), USA, November, 5. – 9. 2001

Fahr, T.; Trinks, H.-P.; Rodig, C.; Schneider, R.;Fischer, C.:In-situ-Hochtemperatur-Neutronenstreu-messungen zur Untersuchung von Phasen- undTexturbildung in Bi-2223/AG Hoch-Tc-SupraleiternDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Feyerherm, R.; Meißner, M.; Ishida, T.:Magnetic-field induced gap and staggeredsusceptibility in the S = 1/2 chain[PMCu(NO3)2(H2O)2]n (PM = pyrimidine)Frühjahrstagung des Arbeitskreises Festkörperphysikder DPG, Hamburg, 26.-30. März 2001

Feyerherm, R.; Loose, A.; Mathonière, C.; Kahn, O.;Ishida, T.:Magnetische Ordnung molekularerÜbergangsmetallkomplexeFrühjahrstagung des Arbeitskreises Festkörperphysikder DPG, Hamburg, 26.-30. März 2001

Findenegg, G.; Schreiber, A.; Smarsly, B.; Hoinkis, E.:In situ SANS study of pore condensation in MCM-41 and SBA-15First Topical Conference on Nanoscale Science andEngineering, Reno(NV), USA, November, 5. – 9. 2001

Fink, D.; Müller, M.; Petrov, A.; Klett, R.;Palmetshofer, L.; Hnatowicz, V.; Vacik, J.; Cervena,J.:Comparison of aqueous marker penetration intolow and high energy ion irradiated polyimide11th Int. Conf. on Radiation Effects in Insulators,Lisbon (Portugal), 3.9.-7.9.2001

Fitter, J.; Herrmann, R.; Hauß, T.; Lechner, R.E.;Dencher, N.A.:Thermische Strukturfluktuationen inBiomolekülen: Die Rolle der PikosekundenDynamik für Stabilität und Aktivität vonmesophilen und thermophilen ProteinenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Fitter, J.; Lechner, R.A.; Dencher, N.A.:The role of picosecond fluctuations for activityand stability in proteinsICNS 2001, Munich, Germany, September 9-13, 2001

Fitzsimmons, M.; Hoffmann, A.; Yashar, P.; Groves,G.; Springer, R.; Arendt, P.; Leighton, S.; Schuller,I.K.; Nogués, J.; Majkzak, C.; Dura, J.; Fritzsche, H.:Influence of temperature and microstructure onmagnetization reversal in Fe- difluoiridesJoint MMM-Intermag, San Antonio, USA, Jan. 7-11,2001

Gierlings, M.:Asymmetry in der Ummagnetiesierung inexchange bias SystemenSeminar der AG Brewer, FU Berlin, 20. 6. 2001

Gierlings, M.; Prandolini, M.J.; Gruyters, M.; Riegel,D.; Brewer, W.D.:Diffuse Streuung an Co/CoO/Au-Exchange-BiasMultilagenArbeitsgruppenseminar AG Brewer, FU Berlin,December 5, 2001

Gierlings, M.; Prandolini, M.J.; Gruyters, M.; Riegel,D.; Brewer, W.D.:Diffuse Streuung an Co/CoO/Au-Exchange-BiasMultilagenSeminar „Magnetismus in Metallen und Schichten“,FU Berlin, 7. 2. 2001

Gierlings, M.; Prandolini, M.J.; Gruyters, M.; Riegel,D.; Brewer, W.D.:About spin polarization at Co/Au and CoO/Auinterfaces studied with low temperature nuclearorientationArbeitsgruppenseminar der AG Schatz, UniversitätKonstanz, January 2001

Gil, A.; Penc, B.; Hofmann, M.; Szytula, A.; ZygmuntA.:Neutron diffraction studies of TbTGe2 (T=Ir,Pt)compounds8th Int. Seminar on Neutron Scattering Investigation inCondensed Matter, Poznañ, 10-12 May, 2001

Gil, A.; Penc, B.; Hofmann, M.; Szytula, A.; ZygmuntA.:Wlasciwosci magnetyczne i strukturamagnetyczna zwiazków miêdzymetalicznychRIrGe2 (R=Gd-Er)Ogólnopolska Konferencja Rozpraszania Neutronów,Chlewiska k/Siedlec 30.09.-3.10.2001 (in Polish)

Gondek, L.; Kolenda, M.; Leciejewicz, J.; Penc, B.;Stüsser, N.; Szytula, A.; Zygmunt, A.; Œlaski M.:Struktury magnetyczne i przejscia fazowe wzwiazkach miêdzymetalicznych ziem rzadkichOgólnopolska Konferencja Rozpraszania Neutronów,Chlewiska k/Siedlec 30.09.-3.10.2001, (in Polish)



260

Gorzel, A.; Graf, H.-A.; Klenke, J.; Rupp, A.:Neutron experiment with a refillable 3He filter cell3. ENPI meeting, Jülich, January 11/12 2001

Gorzel, A.; Habicht, K.; Hutanu, V.; Klenke, J.; Rupp,A.; Wiedenmann, A.:Development and tests of 3He neutron spin filtersand construction of a filling station9th Int. Workshop on Polarized Sources and Targets,Nashville, IN, USA, September 30 – October 4, 2001

Gorzel, A.; Hutanu, V.; Klenke, J.; Rupp, A.:News from the 3He filter project at HMI4. ENPI meeting, Didcot/Abingdon, UK, June 28/292001

Graf, H.A.:Messmöglichkeiten am BerlinerNeutronenstreuzentrum BENSCSeminar „Kristallstrukturuntersuchungenn mitSynchrotron- und Neutronenstrahlen in der Praxis“,Max-Planck-Institut für Festkörperphysik, Stuttgart,17.09.2001

Gruyters, M.:Exchange Bias über nicht-magnetischeZwischenschichtenSeminar „Magnetismus in Metallen und Schichten“,Freie Universität Berlin, 24.1.2001

Habicht, K.:MC simulation of triple axis spectroscopy withneutron resonance spin echoWorkshop on VITESS 2.0 and other Packages forSimulations of Neutron Scattering, Hahn-Meitner-Institut Berlin, 25-27 June 2001

Hauß, T.; Dante, S.; Dencher, N.A.:Interaction of b-amyloid with lipid membranesstudied by neutron diffractionDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hoell, A.; Bley, F.; Wiedenmann, A.; Simon, J.P.;Mazuelas, A.; Boesecke, P.:Composition fluctuations in the demixedsupercooled liquid state of Zr41Ti14Cu12.5Ni10Be22.5:A combined ASAXS and SANS studyID01 Beamline Evaluation, Grenoble, France, May2001

Hoell, A.; Wiedenmann, A.; Simon, J.P.; Bley, F.;Mazuelas, A.; Boesecke, P.:ASAXS und SANS Untersuchungen derZusammensetzungsfluktuationen im entmischtenZustand von Zr41Ti14Cu12.5 Ni10Be22.5

65. Frühjahrstagung der DPG, Hamburg, 26. -30.3.2001

Hoell, A.; Wiedenmann, A.; Simon, J.P.; Bley, F.;Mazuelas, A.; Boesecke, P.:

A combined ASAXS and SANS study ofcomposition fluctuations in the demixedsupercooled liquid state of Zr41Ti14Cu12.5 Ni10Be22.5

ISMANAM, Int. Symposium, Ann Arbor, Michigan,USA, 24. – 29.6.2001

Hofmann, M.; Campbell, S.J.; Knorr, K.; Hull, S.;Ksenofontov, V.:Pressure-induced magnetic transitions inLaMn2Si246th Annual Conference on Magnetism & MagneticMaterials, Seattle, November 12-16, 2001

Jauch, W.:High quality structure factors: benefits from theuse of gamma radiationCentre for Crystallographic Studies, University ofCopenhagen, Denmark, June 18 2001

Javorsky, P.; Prokes, K.; Andreev, A. V.; Sechovsky,V.; Divis, M.; Shiokawa. Y.:Magnetism in UPtAl31iemes Journèes des Actinides, Saint-Malo, 27.4.2001

Kaisermayr, M.; Sepiol, B.; Combet, J.; Pappas, C.;Rüffer, R.; Vogl. G.:Scattering of neutrons and photons -complementary methods for diffusion studiesICNS 2001, Munich, Germany, September 9-13, 2001

Kammel, M.; Hoell, A.; Wiedenmann, A.:Strukturuntersuchung von Magnetitferrofluidendurch Kleinwinkelstreuung mit polarisiertenNeutronen65. Frühjahrstagung der DPG, Hamburg, 26. -30.3.2001

Kammel, M.; Hoell, A.; Wiedenmann, A.:Nanostructures and magnetic correlation inmagnetite-ferrofluids studied by SANS9th Int. Conference on Magnetic Fluids, Bremen,Germany, 23. – 27.07.2001

Keiderling, U.; Seydel, J.; Winterer, M.; Wiedenmann,A.; Hahn, H.:Time-resolved in-situ sans investigation of thesintering behavior of nanocrystalline Y2O3-dopedZrO2 cramics7th European Conference On Advanced MaterialsEuromat 2001, Rimini, Italy, 10.06.-14.06.2001

Keller, T.; Schneider, H.; Klamm, H.; Ohl, M.; Keimer,B.; Habicht, K.:The NRSE-TAS spectrometer at the FRM-IIICNS 2001, Munich, Germany, September 9-13, 2001

Kikkinides, E.S.; Steriotis, Th.A.; Bourganos, V.N.:Digitized representation of the structure of porousmaterials and determination of transportproperties3rd Panhellenic Scientific Conference on ChemicalEngineering, Athens, May 31-June 2, 2001



261

Kirsch, R.; Riegel, D.:Magnetische Wechselwirkungen in Legierungen,SpinkopplungenSeminar der AG Brewer, FU Berlin, 20. 6. 2001

Kiselev, M.A.:The study of phospholipid orientation in strongmagnetic fieldSeminar in Frank Laboratory of Neutron Physics,Joint Institute of Nuclear Research, Dubna,30.03.2001

Kolenda, M.; Baranda, M.; Hofmann, M.; Penc, B.;Szytula A.:Struktury magnetyczne zwiazków RPd2Ge (R=Tb-Er)Ogólnopolska Konferencja Rozpraszania Neutronów,Chlewiska k/Siedlec 30.09.-3.10.2001 (in Polish)

Kranold, R.; Kammel, M.; Hoell, A.:Effect of water on the phase separationcharacteristics of a soda-lime-silica glass19. Int. Congress on Glass, Edinburgh, Scotland, 02.– 06.07.2001

Krist, Th.:Supermirror polarisers made at HMI BerlinENPI III Meeting, Jülich, Germany, January 11-12,2001

Krist, Th.:Development of neutron optical elementsSeminarvortrag Argonne National Laboratories,Argonne, USA, July 24, 2001

Krist, Th.:Neutron optical elements made at HMILos Alamos National Laboratories, Los Alamos, USA,July 26, 2001 (Seminarvortrag)

Krist, Th.:Solid state neutron polarisers and collimatorsInt. Symposium on Optical Science and Technology(SPIE), Neutron and Hard X-Ray Optics andApplications, San Diego, USA, August 2, 2001

Krist, Th.:Solid state neutron optical elements7th ESS General Meeting, Seggau, Austria,September 26.–29, 2001

Krist, Th.; Zsigmond, G.:Simulation of the polarising beam splitter atBENSCWorkshop on VITESS and other packages forSimulations of Neutron Scattering, HMI, Berlin, June,25-27, 2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H; Hussey, N.E.:

Field-induced antiferromagnetism in a high-temperature superconductorDepartment of Physics, Stanford University, Stanford,U.S.A., June 2001 (seminar talk)

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H. Hussey, N.E.:Antiferromagnetic order induced by an appliedmagnetic field in a high-temperaturesuperconductorDepartment of Physics, Oxford University, Oxford,U.K, Oct 2001 (seminar talk)

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H. Hussey, N.E.:New results on the magnetism of single layercuprate LSCOAspen winter conference on superconductivity,January 22-26, 2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H,; Hussey, N.E.:Quantum criticalitySpectroscopy of superconductors (SNS)conference -May 12-17, 2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H.Hussey, N.E.:New results on the magnetism of single layercuprate LSCOEuropean meeting on vortices – Norway,- June 21-24,2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H. Hussey, N.E.:Edge states in quantum spin liquidsMeeting on transition metal oxide, MPI Dresden, July15-18, 2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H.;Hussey, N.E.:Spin magnetism of the vortex state in thecupratesGordon Conference on superconductivity, Oxford(UK), Sept 9-14, 2001



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Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Vordewisch, P.; Smeibidl, P.; Mankorntong, N.;Sasagawa, T.; Nohara, M.; Takagi, H,; Hussey, N.E.:Magnetism of the vortex state in the cupratesSwiss Condensed Matter Meeting, Les Diablerets,Oct. 1-2, 2001

Lappas, A.:Crystal structure and magnetism in low-dimensional compounds PbNi2-xAxV2O8

(A= Mg2+, Co2+)Department of Materials Science and Technology,University of Ioannina, Ioannina, Greece; 19 October2001 (seminar talk)

Lechner R.E.:QENS TOF-spectrometers at continuous andpulsed sourcesESS General Meeting, Seggau, Austria, 27th-29th

Sept. 2001

Lieutenant, K.; Zsigmond, G.; Fromme, M.:ESS simulations in VITESSComputer simulation on existing and projectedneutron instruments by use of the McStas package,Roskilde, Denmark, January 24-27, 2001

Lo Celso, F.; Triolo, A.; Bronstein, L.; Zwanziger, J.;Strunz, P.; Lin, J.S.; Crapanzano, L.; Triolo, R.:Investigating self-assembly and metalnanoclusters in aqueous Di-block copolymerssolutionsICNS 2001, Munich, Germany, September 9-13, 2001

Lonkai, Th.; Hohlwein, D.; Ihringer, J.; Prandl, W.:Magnetische Ordnung in HoMnO3 und YMnO3:ein kohärentes oder inkohärentesProblem?9. Jahrestagung der Deutschen Gesellschaft fürKristallographie, Bayreuth, Germany, 03.12-15, 2001

Lonkai, Th.; Hohlwein, D.; Ihringer, J.; Prandl, W.:The magnetic structure of YMnO3-d and HoMnO3ICNS 2001, Munich, Germany, September 9-13, 2001

Maksimov, I.; Baabe, D.; Süllow, S.; Klauss, H. H.;Litterst, F. J.; Feyerherm, R.; Többens, D.;Matsushita, A.:Interdependence of structural and ground stateproperties in Fe2VAlDPG - Tagung, Hamburg, March 2001

Maletta, H.; Rehm, Ch.; Klose, F.; Fieber-Erdmann,M.; Holub-Krappe, E.:Anomalous effects of hydrogen absorption in Nbfilms4th Intern. Symposium on Metallic Multilayers,MML’01, Aachen, June 24 – 29, 2001

Matas,S.:The E10 2-axis diffractometer3He Summer School-European Research and

Training Network, Frauenchimsee, Germany, 27-31.Aug. 2001

Mezei, F.:The time variable in neutron scatteringexperiments and the ESSESF Exploratory Workshop on Time-resolvedInvestigations of Structural Changes in Soft and SolidMatter with Neutrons and X-rays, Sommerfeld/Berlin,Germany, September 5-7, 2001

Mezei, F.:Detectors for the next generation of neutronsourcesInt. Workshop on Position-Sensitive NeutronDetectors, Status and Perspectives, Berlin, June 28.-30, 2001

Mezei, R.; Russina, M.; Russina, O.:New multiplexing concepts to enhance theefficiency of use of pulsed sourcesICNS 2001, Munich, Germany, September 9-13, 2001

Nørgaard Toft, K. ; Abrahamsen, A.B.; Andersen,N.H.; Lefmann, L.; Hedegård, P.; Jensen, J.;Eskildsen, M.R.; Canfield, P.C.; Klenke, J.; Smeibidl,P.; Kausche, S.:Evidence of strong interaction betweensuperconductivity and magnetism in ErNi2B2CSwiss-Danish Workshop on Neutron Scattering, PSI,November 16-17th 2001

Pappas, C.:Dynamic scaling in spin glassesMonash University, Melbourne, Australia, 24.8.2001

Pappas, C.; Mezei, F.; Ehlers, G.; Campbell, I.A.Dynamic scaling in spin glasses : NSE results andtheoryICNS 2001, Munich, Germany, September 9-13, 2001

Pappas, C.; Mezei, F.; Ehlers, G.; Campbell, I.A.:Experimental evidence for dynamic scaling inspin glassesICNS 2001, Munich, Germany, September 9-13, 2001

Passell, L.; Seeger, P.A.; Daemen, L.; Wang, X.; Lee,W-T.; Zsigmund, G.; Farhi, E.; Saroun, J.:A model instrument for Monte Carlo codecomparisonsICNS 2001, Munich, Germany, September 9-13, 2001

Pirogov, A.; Park, J.; Jo, Y.; Park, J.-G.; Prokes, K.;Welzel, S.; Lee, C.H.; Kudrevatykh, N.; Valiev, E.;Kazantsev, V.; Sheptyakov, D.:Magnetization and magnetic anisotropy of Tm-and Fe-subsystems in Tm2Fe17

Euro-Asian Symposium: Trends in Magnetism,Ekaterinburg, 1.3.2001

Poeste, T.:Mikrostrukturelle Veränderungen im SystemBremse



263

AK „Werkstoffkundliche Aspekte des Verschleißesund der Zerspannung“ der DGM, Kaiserslautern,29.03.2001

Prokes, K.; et al.:Neutron scattering experiments in magnetic fieldsat HMIInt. Workshop on The Present Status of HighMagnetic Field Technology and the Prospects forApplications to Neutron Scattering Experiments, HMIBerlin, 29. 5. 2001

Prokes, K.; Javorsky, P.; Sechovsky, V.; P.; Gukasov,A.; Brück, E.:Stability of the antiferromagnetic structure ofUNiAl in magnetic fields31iemes Journèes des Actinides, Saint-Malo, 27.4.2001

Pyzalla, A.:Experimentelle Analysen der Gefüge-, Textur- undSpannungsentwicklung bei der Umformungmehrphasiger WerkstoffeKolloquium der DFG, Bonn, 11.09.-12.09.2001

Pyzalla, A.:In-situ Analysen mit weißer hochenergetischerRöntgen-SynchrotronstrahlungSitzung Fachausschuss Eigenspannungen,Schweinfurt, 14.11.-15.11.2001

Py za lla , A .:Hartmagnetische Werkstoffe und ihre technischeAnwendungHabilitationsvortrag, Ruhr-Universität Bochum,20.07.2001

Pyzalla, A.; Wild, E.; Wang, L.; Wroblewski, T.:Ch an ges in m icrostru ctu re, texture a nd res id ualstre sse s o n the su rface of a ra il re sultin g fro mfric tio n a nd we arWear 2001, Vancouver, Canada, 25.04.2001.09.-13.09.2001

Reehuis, M.:Techniques for the determination of crystal andmagnetic structuresMax-Planck-Institut für Festkörperforschung,Stuttgart, 20.07.2001

Reehuis, M.:Techniques for the determination of crystal andmagnetic structuresUniversität Augsburg, 22.11.2001(Kolloquiumsvortrag)

Reimers, W.; Pyzalla, A.:Messmöglichkeiten zur Eigenspannungsanalysean SynchrotronstrahlungsquellenSitzung Fachausschuss Eigenspannungen,Schweinfurt, 14.11.-15.11.2001

Rekveldt, M.Th.:

Spin-echo small-angle neutron scattering andhigh resolution larmor diffractionPAC-meeting, Dubna, Russia, 27 april 2001

Rogl, P.; Gukasov, A.; Matas, S.; Mihalik, M.;Czopnik, A.; Troc, R.; Tran, V.H.; Menovsky, A.A.:Magnetic order in U3Al2Si3 compounds11th Czech and Slovak Conference on Magnetism,Kosice, Slovakia, 20-23. Aug. 2001

Rousseau, D.; Marty, J.-D.; Mauzac, M.; Martinoty, P.;Brandt, A.; Guenet, J.-M.:Conformation in solution of side-chain liquidcrystal polymers as a function of the mesogengraft-amountUniversität Bayreuth, Physik. Institut, TheoretischePhysik III, Nov. 27, 2001 (seminar talk)

Rüegg, Ch.; Cavadini, N.; Furrer, A.; Kräemer, K.;Güdel, H.U.; Vorderwisch, P.; Mutka, H.:Spin dynamics in the high field phase of quantumcritical S=1/2 TlCuCl3ICNS 2001, Munich, Germany, September 9-13, 2001

Rüegg, Ch.; Cavadini, N.; Furrer, A.; Kräemer, K.;Güdel, H.U.; Vorderwisch, P.; Mutka, H.:Spin dynamics in the high field phase of quantumcritical S=1/2 TlCuCl32001 Swiss Workshop on Materials with NovelElectronic Properties, les Diablerets, Switzerland,October 1-3, 2001

Schöttl, S.; Meißner, M.; Günther, D.:Specific heat of heavy fermion systems,exemplified with UPt3

Physikalisch-Technische Bundesanstalt, Berlin,November 2001

Schöttl, S.; Siemensmeyer, K.; Boiko, V.; Bat’ko, I.;Dwight-Adams, E.; Sherline, T.E.:Neutronenstreuexperiment an festen 3HeDeutsche Physikalische Gesellschaft, Hamburg, 26.-30. März, 2001

Schuck, G.; Lechner, R. E.; Langer, K.:Proton conduction based on intracrystallinechemical reactionICNS 2001, Munich, Germany, September 9-13, 2001

Schwendel, D.; Hayashi, T.; Steitz, R.; Dahint, R.;Pipper, J.; Persin, A.J.; Grunez, M.:Interaction of water with protein resistent self-assembling monolayers: Neutron reflectivitymeasurements of water density in the interphaseregionICNS 2001, Munich, Germany, September 9-13, 2001

Sechovsky, V.; Andreev, A. V.; Syshchenko, O.;Prokes, K.; Bartachevich, M.I.; Goto, T.:On the treshold of long-range magnetic order:UNi2/3Rh1/3Al and UCoAl study11th Czech and Slovak Conference on MagnetismCSMAG’01, Kosice, 22.8. 2001



264

Sechovsky, V.; Prokes, K.; Honda, F.; Khmelevski,S.; Ouladdiaf, B.; Kulda, J.:Pressure-induced magnetic structures in UNiGaICNS 2001, Munich, Germany, September 9-13, 2001

Sitepu, H.; Khalil Allafi, J.; Schmahl, W.W.; Eggeler,G.;Többens, D.M.:An in-situ neutron diffraction study of themartensitic transformation in aged Ni-rich NiTialloysInt. Conference on Martensitic Transformation(ICOMAT02), Helsinki, Finland, June 18-23, 2001

Sitepu, H.; Schmahl, W.W.; Khalil Allafi, J.; Eggeler,G.; Reinecke, T.; Brockmeier, H.G.; Tovar, M.;Többens, D.M.:A quantitative analysis of martensitic phases andtheir crystallographic texture in an aged Ni-richNiTi alloy using x-ray and neutron diffraction dataInt. Conference on Shape Memory Alloys andSuperelastic Technologies and Shape MemoryMaterials, Kunming, China, September 2-7, 2001

Steitz, R.; Howse, J.; Schemmel, S.; Pohlers, A.;Uredat, S.; Findenegg, G.H.:Ultrathin surfactant layers adsorbed at thepolymer/solution interface100. Bunsentagung, Stuttgart, 24.-26. 5. 2001

Steitz, R.; Leiner, V.; Tauer, K.; Khrenov, V.; v.Klitzing, R.:Temperature induced changes in polyelectrolytefilms at the solid-liquid interfaceICNS 2001, Munich, Germany, September 9-13, 2001

Steitz, R.; Schemmel, S.; Howse, J.; Uredat. S.;Findenegg, G.H.:Adsorption layers of CmEn surfactants at thepolymer/solution interface40. Hauptversammlung der Kolloid-Gesellschaft e.V.,Potsdam, 24.-26. 9. 2001

Stock, C.; Genzel, Ch.:Eigenspannungsanalyse mit weißer,mittelenergetischer RöntgenstrahlungSitzung Fachausschuss Eigenspannungen,Schweinfurt, 14.11.-15.11.2001

Szytula, A.; Bazela, W.; Gondek, L.; Jaworska-Golub,T.; Penc, B.; Stüsser, N.; Zygmunt A.:Magnetyczne wlasciwosci zwiazków RAuIn(R=Tb,Dy,Ho) w swietle badanneutronograficznychOgólnopolska Konferencja Rozpraszania Neutronów,Chlewiska k/Siedlec 30.09.-3.10.2001 (in Polish)

Toudic, B.; Le Lann, H.; Guillaume, F.; Lechner, R.:Symmetry breaking, pretansitional phenomenaand molecular disorder in an aperiodic molecularcomposite crystalICNS 2001, Munich, Germany, September 9-13, 2001

Triolo, A.; Pappas, C.; Többens, D.; Arrighi, V.:NSE and TOF investigation of coherent dynamicsof atactic polypropylene4th Int. Discussion Meeting on Relaxation in ComplexSystems, IDMRCS2001, Crete (2001)

Triolo, A.; Triolo, R.; Arrighi, V.:QENS evidences of dynamic heterogeneity inpolymer electrolytes4th Int. Discussion Meeting on Relaxation in ComplexSystems, IDMRCS2001, Crete (2001)

Ulbricht, A.; Böhmert, J.; Viehrig, H.-W.:Beziehungen zwischen Microstructur undZähigkeitseigenschaften an neutronenbestrahltenWWER-ReaktordruckbehälterstählenJahrestagung Kerntechnik 2001 (Annual Meeting onNuclear Technology 2001), Dresden, 15.-17. Mai,2001

v. Klitzing, R.; Kolaric, B.; Toca, J.:Influence of polyelectrolytes on the stability offree-standing surfactant filmsNachwuchstagung der Kolloidgesellschaft,Düsseldorf, 28.-29.4.2001

v. Klitzing, R.; Steitz, R.; Leiner, V.:Structure of polyelectrolyte multilayersinvestigated by neutron reflectivityMillenium Symp. des Institut Laue-Langevin,Grenoble, France, 6.4. – 7.4.2001v. Klitzing, R.; V. Leiner, K. Tauer, Krenov, V.; Steitz,R.:Temperature effects of polyelctrolyte multilayersat the solid/liquid interfaceDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Wegener, J.:Mikrostruktur, Textur und Eigenspannungen vonstranggepressten und reibrührgeschweißtenAluminiumlegierungenSitzung Fachausschuss Eigenspannungen,Schweinfurt, 14.11.-15.11.2001

Wesemann, A.:PEE-PEO Diblockcopolymer-Monoschichten ander Wasser-Luft-GrenzflächeSeminar der Angewandten Physik, 10. August 2001

Wesemann, A.; Ahrens, H.; Steitz, R.; Papastavrou,G.; Helm, C.A.:Lateral self-organization at fluid interfaces: inter-and intramolecular interactionsVorbereitungstreffen zum Gutachterkolloquium desSchwerpunktprogramms „Benetzung“, 18.-20. Juli,2001

Willumeit, R.; Förster, F.; Funari, S.; Hauß, T.; Hubo,S.; Kruse, M.; Andrä, J.:The interaction of the synthetic peptide NK2 withmodell membranesICNS 2001, Munich, Germany, September 9-13, 2001



265

Wilmer, D.:Kohäarente quasielastische Neutronenstreuungzur Charakterisierung ionenleitender RotorphasenLehrstuhl für Kristallographie und Strukturphysik(Prof. A. Magerl), Univ. Erlangen, June 7, 2001(seminar talk)

Wilmer, D.; Combet, J.:Natriumdiffusion in festen Lösungen vonNatriumphosphat und NatriumsulfatBunsentagung, Stuttgart, May 24-26

Wilmer, D.; Feldmann, H.; Lechner, R.E.; Combet, J.:Dynamics in ion-conducting rotor phases79th Int. Bunsen Discussion Meeting, Münster,October 10-12, 2001

Zsigmond, G.:The VITESS ProgramComputer simulation on existing and projectedneutron instruments by use of the McStas package.Roskilde, Denmark, January 24-27, 2001

Zsigmond, G.; Krist, T.; Mezei, F.:MC simulations of polarizing cavities7th ESS General Meeting, Seggau, Austria,September 26-29, 2001

Posters

Alava, C.; Arrighi, V.; Cowie, J.M.G.; Cameron, J.D.:SANS studies of solutions and molecularcomposites prepared from cellulose tricarbanilateICNS 2001, Munich, Germany, September 9-13, 2001

Annibali, G.; Bruno, G.; Giuliani, A.; Manescu, A.;Marcantoni, M.; Rustichelli, F.; Turquier, F.:Neutron diffraction measurements for residualstress analysis in automotive steel gearsICNS 2001, Munich, Germany, September 9-13, 2001

Arrighi, V.; Triolo, A.:Segmental dynamics in poly(isobutylene)4th Int. Discussion Meeting on Relaxation in ComplexSystems, IDMRCS2001, Crete (2001)

Auffermann, G.; Schmidt, U.; Bayer, B.; Prots, Yu.;Kniep, R.:Speciation of nitrogen in diazenides11. Tagung Festkörperanalytik, Chemnitz, June, 24 –28, 2001/poster

Baabe, D.; Maksimov, I.; Süllow, S.; Klauss, H.H.;Litterst, F. J.; Feyerherm, R.; Többens, D.;Matsushita, A.:Interdependence of structural and ground stateproperties in Fe2VAlICPME 2001, Oxford UK, September 2001

Baglioni, P.; Berti, D.; Dante, S.; Fratini, E.; Hauss, T.:A structural study of lamellar phases formed bynucleoside functionalized lipidsICNS 2001, Munich, Germany, September 9-13, 2001

Baran, S.; Hofmann, M.; Lampert, G.; Stüsser, N.;Szytula, A.; Többens, D.; Smeibidl, P.; Kausche, S.:Magnetic structures of HoAuGe and ErAuGeICNS 2001, Munich, Germany, September 9-13, 2001

Baszynski, J.; Tolinksi, T.; Idzikowski, B.; Többens,D.M.; Hoser, A.:Neutron and X-ray diffraction studies of bulk andpowdered La0.7Sr0.3MnO3 ceramicsICNS 2001, Munich, Germany, September 9-13, 2001

Bat’ko, I.; Meschke, M.; Kohout; A.; Flachbart, K.;Siemensmeyer, K.:Magnetism of cubic ReB12 – borides: Interplay ofdiploar and RKKY interactions in the fcc-symmetryDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Bat’ko, I.; Flachbart, K.; Kohout, A.; Matas, S.;Meschke, M.; Siemensmeyer, K.; Schitsevalova, N.;Paderno, Y.:Magnetic order in the fcc-symmetry: Phasediagram and structure of ReB12ICNS 2001, Munich, Germany, September 9-13, 2001

Bazela, W.; Gondek, L.; Penc, B.; Stüsser, N.;Szytula, A.; Zygmunt, A.:Crystal and magnetic structure of TbAuIn andHoAuIn compounds20th European Crystallographic Meeting ECM 20,Kraków, Poland, 25-31.08.2001

Bazela, W.; Gondek, L.; Penc, B.; Stüsser, N.;Szytula, A.; Zygmunt, A.:Neutron diffraction studies of the crystal andmagnetic structures of TbAuIn and HoAuIncompounds43rd Polish Crystallographic Meeting, Wroclaw,Poland, 28-29.06.2001

Beirne, E.; McEwen, K.A.; Habicht, K.:Magnetic excitations in single crystal PrNiSnICNS 2001, Munich, Germany, September 9-13, 2001

Berti, D.; Baglioni, P.; Baldelli Bombelli, F.; Keiderling,U.:Living polynucleotides formed by thespontaneous aggregation ofdilauroylphospholiponucleosidesXV Conference of the European Colloid and InterfaceSociety, Coimbra, Portugal, September 16-21, 2001

Bleif, H.-J.; Lechner, R.E.; Russina, M.:New chopper spectrometers for pulsed neutronsourcesESS-WR-Audit, FZ Jülich, 10th December 2001



266

Bleif, H.-J.; Wechsler, D.; Mezei, F.:TOF chopper time-of-flight powder diffractometerICNS 2001, Munich, Germany, September 9-13, 2001

Boiko, V.; Bat’ko, I.; Schöttl, S.; Siemensmeyer, K.;Dwight-Adams, E.; Sherline, T.E.:Neutronenstreuung an festen 3HeDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Bonn, S.; Fritzsche, H.; Hauschild, J.; Klenke, J.;Maletta, H.:Spin density waves of thin epitaxial Cr(110) layersin a V/Cr multiplayerICNS 2001, Munich, Germany, September 9-13, 2001

Bonn, S.; Fritzsche, H.; Hauschild, J.; Maletta, H.:Spindichtewellen dünner Cr(110)-Schichten inintermetallischen VielschichtsystemenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Borowiec, M.; Hofmann, M.; Hoser, A.; Michalski, E.:Neutron structural investigations of para- andantiferroelastic phase of potassium dysprosiumdouble tungstateICNS 2001, Munich, Germany, September 9-13, 2001

Bouwman, W.G.; Uca, O.; Plomp, J.; Grigoriev, S.V.;Kraan, W.H.; Rekveldt, M.Th.:Spin-echo small-angle neutron scatteringexperimentMaterials research 2001, Veldhoven, 8-9 May, 2001

Bouwman, W.G.; Grigoriev, S.V.; Uca, O.; Kraan,W.H.; Plomp, J.; Rekveldt, M.Th.:Applicability of spin-echo small-angle neutronscatteringICNS 2001, Munich, Germany, September 9-13, 2001

Bouwman, W.G.; Uca, O.; Krouglov, T.; Plomp, J.;Grigoriev, S.V.; Kraan, W.H.; Rekveldt, M.Th.:First quantitative test of spin-echo small-angleneutron scatteringFOM-gecondenseerde materie, Veldhoven, TheNetherlands, 18 december 2001

Boyko, V.; Siemensmeyer, K.; Schöttl, S.; Bat'ko, I.;Matas, S.; Dwight-Adams, E.; Sherline, T.E.:Heat exchanger from Pt and Pt/Ag powderInternational Symposium on Quantum Fluids andSolids. July 22-27 2001, Konstanz

Boysen, H.; Lerch, M.; Gilles, R.; Krimmer, B.;Többens, D.:Structure and ionic conductivity in doped LaGaO2

ICNS 2001, Munich, Germany, September 9-13, 2001

Branca, C.; Faraone, A.; Magazù, S.; Maisona, G.;Mangione, A.; Pappas, C.; Triolo, A.:Characterization of trehalose aqueous solutionsby neutron spin echo


Bronger, W.; Müller, P.; Böhmer, M.:Na6MnS4, magnetfeldabhängigeNeutronenbeugungsexperimenteDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Brunauer, G.; Frey, F.; Boysen, H.; Schneider, H.;Fischer, P.; Hansen, Th.; Többens, D.; Ehrenbuerg,H.:Neutron diffraction study up to 1900K of 3:2mulliteICNS 2001, Munich, Germany, September 9-13, 2001

Bruno, G.; Ceretti, M.; Girardin, E.; Giuliani, A.;Manescu, A.; Rustichelli, F.:Neutron diffraction measurements of ResidualStresses in Aerospace MMC MaterialsICNS 2001, Munich, Germany, September 9-13, 2001

Bruno, G.; Nitschke-Pagel, T.:The residual stress relaxation after fatique in finegrained steelsICNS 2001, Munich, Germany, September 9-13, 2001

Bruno, G.; Pinto, H.; Reimers, W.:g-formation and growth in the nickelbase superalloy SC 16ICNS 2001, Munich, Germany, September 9-13, 2001

Calandrini, V.; Deriu, A.; Onori, G.; Lechner, R. E.;Pieper, J.:Dynamic features of hydration water interactingwith hydrophobic moleculesICNS 2001, Munich, Germany, September 9-13, 2001

Calandrini, V.; Deriu, A.; Onori, G.; Lechner, R.E.;Pieper, J. : Water dynamics in dilute aqueous solutions ofsmall apolar solutes by quasi-elastic neutronscatteringICNS 2001, Munich, Germany, September 9-13, 2001

Cavadini, N.; Rüegg, Ch.; Furrer, A.; Güdel, H.U.;Krämer, K.; Mutka, H.; Wildes, A.; Habicht, K.;Vorderwisch, P.:Triplet modes in a quantum spin liquid across thecritical field4. Physical Phenomena at High Magnetic FieldsConference, Santa Fe, New Mexico, October 19-25,2001

Charalambopoulou, G. Ch.; Steriotis, Th. A.; Hauss,Th.; Stefanopoulos, K. L.; Stubos, A. K.:A neutron diffraction study of the effect ofhydration on stratum corneum structureICNS 2001, Munich, Germany, September 9-13, 2001

Charalambopoulou, G. Ch.; Steriotis, Th. A.;Kikkinides, E. S.; Stubos, A. K.; Stefanopoulos, K. L.;Kanellopoulos, N. K.; Papaioannou, A. Th.:



267

Characterisation of structural properties ofstratum corneum2nd Mediterranean Meeting „New Perspectives inControlled Release“, Athens, April 27-30, 2001

Charalambopoulou, G. Ch.; Steriotis, Th. A.;Stefanopoulos, K. L.; Kikkinides, E. S.; Stubos, A. K.:The combination of neutron scattering techniquesfor the study of hydration of porcine stratumcorneumStratum Corneum III, Basel,Switzerland, September12-14, 2001

Chatterji, T.; Schneider, R.P.; Hoffmann, J.-U.;Hohlwein, D.; Suryanarayanan, R.; Dhalenne, G.;Revcolevschi, A.:Diffuse magnetic scattering in quasi-2DLa1.2Sr1.8Mn2O7


Danilkin, S.; Delafosse, D.; Fuess, H.; Gavriljuk, V.;Ivanov, A.; Magnin, T.; Wipf, H.:Hydrogen vibrations in austenitic stainless steelICNS 2001, Munich, Germany, September 9-13, 2001

Davies, S.M.A.; Harroun, T.H.; Darkes, M.J.M.;Hauss, T.; Cornell, R.B.; Bradshaw, J.P.:A neutron study of lipid sensing by the membranebinding domain of phosphocholinecytidylyltransferase673rd Meeting of the British Biochemical Society,Bristol, U.K., April 10 – 12, 2001

Deen, P.P.; Goff, J.P.; Toader, A.M.; Klenke, J.;Yakhou, F.; Ward, R.C.C.; Wells, M.R.:Long-range magnetic order in intermediate-valence Ce-Lu alloysICNS 2001, Munich, Germany, September 9-13, 2001

Desmedt, A.; Guillaume F.; Soetens, J.C.; Dianoux,A.J.; Lechner R.E.:Molecular dynamics and phase transitions inthiourea intergrowth crystalsICNS 2001, Munich, Germany, September 9-13, 2001

Desmedt, A.; Guillaume, F.; Soetens, J.C.; Couzi, M.;Dianoux, A.J.; Lechner, R.E.:Dynamique moléculaire et transitions de phasedans les cristaux organiques d'intercroissancecyclohexane / thiourée et chlorocyclohexane /thiourée10ème Edition des Journées de la DiffusionNeutronique - Rencontres Rossat-Mignod, Tregastel,May 16-18, 2001

di Stefanis, A.; Steriotis, Th. A.; Tomlinson, A. G.;Keiderling, U.:SANS characterization of pillared layeredcatalystsICNS 2001, Munich, Germany, September 9-13, 2001

Dieter, S.; Pyzalla, A.; Reimers, W.:

Textur- und Eigenspannungsanalysen anVerschleißschutzschichten für MikrozahnräderKolloquium Material- und Verfahrensentwicklung fürmikrotechnische Hochleistungsbauteile,Forschungszentrum Karlsruhe, 23.10.2001

Dieter, S.; Pyzalla, A.; Wanderka, N.; Macht, M.-P.;Reimers, W.:Eigenspannungen, Textur und Koerzitivfeld inAbhängigkeit von den Sputterparametern fürFeCo/SiO2 – SchichtenKolloquium Material- und Verfahrensentwicklung fürmikrotechnische Hochleistungsbauteile,Forschungszentrum Karlsruhe, 23.10.2001

Donath, E.; Dähne, L.; Sukhorukov, G. B.; Moya, S.;Antipov, A.; Leporatti, S.; Ibarz, G.; Radchenko, I.;Gao, C.; Qiu, X.; Estrela-Lopis, I.; Möhwald, H.:From self-assembled multilayers to drug carriers;nano-reactors and artificial cellsConference on Assembly and Self-assembly at theInterface of Biology, Chemistry and Physics Il, Ciollo,Italy, 20-25.08.2001

Dreyhaupt, A.; Kreyßig, A.; Krug, K.; Dörr, M.; Rotter,M.; Ritter, C.; Vettards, E.; Grenier, B.; Prokes, K.;Winzer, K.; Loewenhaupt, M.:Charakterisierung magnetischer Phasen inDyNi2B2C im externen Magnetfeld parallel zur a-RichtungDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Ehlers, G.; Farago, B.; Pappas, C.; Mezei, F.:A new IN11 with an almost 35 times highercounting rate than that of IN11CMillenium Workshop, ILL, Grenoble, France, April 6-7,2001

Ehlers, G.; Ritter, C.; Schneider, R.; Knorr, K.;Maletta, M.:Pressure-induced change of magnetic order inTb1-xYxNiAl and TbNi1-xCuxAlICNS 2001, Munich, Germany, September 9-13, 2001

Fahr, T.; Schneider, R.; Trinks, H.P.; Fischer, C.:Investigation of the formation of the Bi-2223phase in multifilamentary Bi-2223/Ag tapes by insitu high temperature neutron diffractionDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Fernandez, R.; Bruno, G.; Borrego, A.; Gonzalez-Doncel, G.; Pyzalla, A.:Determination by neutron diffraction of residualstress in PM 6061 Al – 15 vol.-% SiC compositeswith different whisker orientationICNS 2001, Munich, Germany, September 9-13, 2001

Fernández, R.; Bruno, G.; Borrego, A.; González-Doncel, G.; Pyzalla, A.:



268

Determination of residual stresses in 6061Al-15%SiCw composites with different whiskerorientation/distributionICNS 2001, Munich, Germany, September 9-13, 2001

Feyerherm, R.; Loose, A.; Lawandy, M. A.; Li, J.:Crystal and magnetic structure of the two-dimensional coordination polymers CoCl2(bpy-d8)and NiCl2(bpy-d8) (bpy-d8 = 4,4’-bipyridine-d8)ICNS 2001, Munich, Germany, September 9-13, 2001

Feyerherm, R.; Welzel, S.; Sutter, J. P.; Kahn, O.:Magnetische Ordnung in der organischenVerbindung 4,5-dimethyl-1,2,4-triazol-nitronyl-nitroxidFrühjahrstagung des Arbeitskreises Festkörperphysikder DPG, Hamburg, 26.-30. März 2001

Feyerherm, R.; Loose, A.; Ishida, T.; Nogami, T.;Mathonière, C.; Kahn, O.:Single crystal studies of the 1-D systemsPMCu(NO3)2(H2O)2 and MnNi(NO2)4(en)ESF Conference on Molecular Magnets, Davos, 10.-15. März 2001

Fink, D.; Petrov, A.; Müller, M.:Marker penetration into high energy ion irradiatedpolymers12th Int. Conf. on Surface Modifications of Materialsby Ion Beams, Marburg (Germany) 9.9.-14.9.2001

Fritzsche, H.; Temst, K.; van Bael, M. J.:Off-specular polarized neutron reflectometry froma periodic array of Co-disksICNS 2001, Munich, Germany, September 9-13, 2001

Füzi, J.; Golub, R.; Mezei, F.; Rosta, L.:Accuracy evaluation of hexapole electromagnetsICNS 2001, Munich, Germany, September 9-13, 2001

Geissler, J.; Goering, E.; Weigand, F.; Justen, M.;Schütz, G.; Langer, J.; Schmitz, D.; Maletta, H.;Mattheis, R.X-ray resonant magnetic reflectometry as apowerful tool for element specific magnetizationdepth profiling4th Intern. Symposium on Metallic Multilayers,MML’01, Aachen, June 24 – 29, 2001

Gierlings, M.; Prandolini, M. J.; Fritzsche, H.;Gruyters, M.; Riegel, D.:Polarised neutron reflection (PNR) study on themagnetisation reversal inferromagnetic/antiferromagnetic Co/CoOmultilayersICNS 2001, Munich, Germany, September 9-13, 2001

Gierlings, M.; Prandolini, M.J.; Fritzsche, H.; Gruyters,M.; Riegel, D.:The magnetization reversal process in a[Co/CoO/Au]20 exchange bias multilayer above TNstudied with polarized neutron reflectometry(PNR)


Gierlings, M.; Prandolini, M.J.; Gruyters, M.; Riegel,D.; Brewer W.D.:On the possibility of detecting asymmetricmagnetization reversal processes in exchangebias systems using low temperature nuclearorientationSymposium on Metallic Multilayers (mml), Aachen,June 24 – 29, 2001

Gil, A.; Kolenda, M.; Hofmann, M.; Penc, B.; Oleœ,A.; Zygmunt, A.:Magnetic phase transitions in TbTX2 (T=d-electronelements, X=Ge and Sb)XII School of Modern Physics, Ladek Zdrój, June 21-24, 2001

Gilles, R.; Mukherji, D.; Többens, D.M.; Strunz, P.;Barbier, B.; Rösler, J.; Fuess, H.:Neutron -, X-ray - and electron diffractionmeasurements for the determination of g/g latticemisfit in Ni-base superalloysICNS 2001, Munich, Germany, September 9-13, 2001

Gilles, R.; Strunz, P.; Mukherji, D.; Wiedenmann, A.;Roesler, J.; Fuess, H.:g’-precipates dissolution in Ni-base superalloy: insitu SANS investigationDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Gorzel, A.; Klenke, J.; Rupp, A.:Entwicklung von3He-Neutronenspinfilterzellen amHMIFrühjahrstagung des Arbeitskreises Festkörperphysikbei der DPG, Hamburg, March 26 – 30 2001

Gorzel, A.; Klenke, J.; Wiedenmann, A.; Rupp, A.:Development of 3He neutron spin filter cells at theHMIICNS 2001, Munich, Germany, September 9-13, 2001

Gratz, E.; Markosyan, A.; Pau-Boncour, V.; Hoser, A.;Gaidukova, I.; Rodimin, V.:Sublattice magnetisations in ErCo3


Gutberlet, T.; Frank, J.; Hoell, A.; Kammel, M.;Katsaras, J.:Structure and phase behaviour of magneticallyaligned biomimetic substratesJahrestagung d. Deutschen Gesellschaft f. Biophysik,Münster, Germany, September, 2001

Gutberlet, T.; Hoell, A.; Kammel, M.; Frank, J.;Katsaras, J.:Neutron scattering from magnetically alignedbiomimetic substratesICNS 2001, Munich, Germany, September 9-13, 2001

Gutberlet, T.; Hoell, A.; Kammel, M.; Katsaras J.:



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Neutron scattering from magnetically alignedbiomimetic substratesDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Gutberlet, T.; Steitz, R.; Howse, J.; Klösgen, B.:Lipid bilayers on a polymer grafted Si-substrateDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Gutberlet, T.; Steitz, R.; Howse, J.; Estrela-Lopis, I.;Klösgen, B.:Hybrid biomembrane substructure determinationby contrast variation analysisICNS 2001, Munich, Germany, September 9-13, 2001

Gutberlet, T.; Steitz, R.; Klösgen, B.:Structure of phospholipid bilayers adsorbed topolymer coated surfaces45. Annual Meeting Biophysical Society, Boston, 2001(abstract in Biophys. J., 80, 2001)

Hauschild, J.; Fritzsche, H.; Bonn, S.; Liu, Y.; Klenke,J.; Prokes, K.:Determination of the temperature dependence ofthe coercivity in Fe/Cr(110) multilayersICNS 2001, Munich, Germany, September 9-13, 2001

Hauß, T.; Dante, S.; Dencher, N.A.:Interaction of b-amyloid with lipid membranesstudied by neutron diffractionDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hauß, T.; Dante, S.; Dencher, N.A.:Interaction of Alzheimer’s b-amyloid with anionicand zwitterionic lipid membranesICNS 2001, Munich, Germany, September 9-13, 2001

Hauß, T.; Dante, S.; Dencher, N.A.:Localization of Alzheimer’s b-amyloid in chargedand uncharged lipid membranes. A neutrondiffraction study4th Int. Conference on Biological Physics, Kyoto,Japan, July 30 – August 3, 2001

Häußler, F.; Palzer, S.; Eckart, A.; Hoell, A.:Microstructural SANS - studies on hydratingtricalcium silicate (C3S)ICNS 2001, Munich, Germany, September 9-13, 2001

Häußler, F.; Palzer, S.; Eckart, A.:SANS - Untersuchungen zu Veränderungen in derNanostruktur von hydratisierendemTricalciumsilicatDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Heinrich, M.; Pyckhout-Hintzen, W.; Richter, D.;Straube, E.; Wiedenmann, A.:SANS investigations of relaxation dynamics ofentangled model H-polymer

Deutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hernandez-Velasco, J.; Sáez-Puche, R.; Hoser, A.;Rodriguez-Carvajal, J.:Low temperature incommensurate magnetic orderin R2BaCoO5 (R=rare earth)ICNS 2001, Munich, Germany, September 9-13, 2001

Hoell, A.; Kammel, M.; Wiedenmann, A.:Nanostructures and magnetic correlations inFerrofluids studied by SANSICNS 2001, Munich, Germany, September 9-13, 2001

Hoell, A.; Müller, R.; Wiedenmann, A.; Gawalek W.:Core-shell and magnetic structure ofBariumhexaferrite fluids studied by SANS9th Int. Conference on Magnetic Fluids (ICMF9),Bremen, Germany, 23. – 27.7.2001

Hoffmann, J.-U.; Hohlwein, D.; Schneider, R.;Moudden, A.H.:Magnetic short-range order in La0.9Sr0.1MnO3


Hoffmann, J.-U.; Hohlwein, D.; Schneider, R.;Moudden, A.H.:Kurzreichweitige magnetische Ordnung inLa1-xSrxMnO3


Hofmann, M.; Campbell, S.J. Edge, A.V.J.:Valence and magnetic transitions inYbMn2Si2-xGex


Hofmann, M.; Campbell, S.J.:Mixed magnetic interactions in La1-xYxMn2Si2-neutron diffraction and Mössbauer spectroscopyDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hofmann, M.; Campbell, S.J.; Kaczmarek, W.A.:Mechanochemical treatment of a-Fe2O3-microstructural analysisICNS 2001, Munich, Germany, September 9-13, 2001

Hohlwein, D.:Magnetische Wechselwirkungen und Onsager-Reaktionsfeld aus paramagnetisch-diffuserNeutronenstreuungDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hohlwein, D.:Magnetic interactions and Onsager reaction fieldfrom paramagnetic diffuse neutron scatteringICNS 2001, Munich, Germany, September 9-13, 2001

Hoinkis, E.; Röhl-Kuhn, B.:



270

The spatial distribution of vapor filled voids oncondensation and drainage of nitrogen at ~ 78 Kin a mesoporous silica glassProc. 7th Int. Conf. on Fundamentals of Adsorption.Nagasaki, May 20 -25 (2001)

Hölzel, M.; Danilkin, S.; Hoser, A.; Wieder, T.; Fuess,H.:Phonon dispersion in nitrogen doped austeniticsteelsDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Hölzel, M.; Danilkin, S.; Hoser, A.; Ehrenberg, H.;Wieder, T.; Fuess, H.:Phonon dispersion in austenitic stainless steelFe-18Cr-12Ni-2MoICNS 2001, Munich, Germany, September 9-13, 2001

Hoser, A.; Stüßer, N.; Schotte, U.; Meschke, M.;Meißner, M.:Incommensurate-commensurate phase transitionin the frustrated antiferromagnet CsCuCl3ICNS 2001, Munich, Germany, September 9-13, 2001

Howse, J.; Uredat, S.; Steitz, R.; Findenegg, G.H.:Surfactant adsorption to thin polymer-coatings asstudied by neutron reflectometryDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Huster, D.; Vogel, A.; Binder, H.; Zschörnig, O.;Gutberlet, T.; Katzka, C.; Kadereit, D.; Kuhn, K.;Waldmann, H.; Arnold, K.:Investigation of a membrane bound ras peptide byFTIR, neutron diffraction, and solid state NMRspectroscopyJahrestagung der Deutschen Gesellschaft fürBiophysik, Münster, 2001

Janousová, B.; Svoboda, P.; Sechovsky, V.; Prokes,K.; Nakotte, H.; Ouladdiaf, B.; Císarová, I.:Neutron diffraction study of CePtSnICNS 2001, Munich, Germany, September 9-13, 2001

Jauch, W.; Peters, J.:Correction for thermal diffuse scattering in singlecrystal time-of-flight neutron diffractionICNS 2001, Munich, Germany, September 9-13, 2001

Jaworska-Gotab, T.; Szytula, A.; Zygmunt, A.;Stüsser, N.; Haen, P.:Magnetic properties of HoRh2-xPdxSi2 solidsolutions investigated by magnetometricmeasurements and neutron diffraction20th European Crystallographic Meeting ECM 20,Kraków, Poland, 25-31.08.2001

Kaisermayr, M.; Pappas, C.; Triolo, A.; Vogl, G.:NSE for self-diffusion in intermetallic alloysICNS 2001, Munich, Germany, September 9-13, 2001

Keiderling, U.:

The new "BerSANS-PC" software for reductionand treatment of small angle neutron scatteringdataICNS 2001, Munich, Germany, September 9-13, 2001

Keller,T.; Habicht, K.; Rekveldt, M.Th.:Direct measurement of ∆d/d by neutron larmordiffractionICNS 2001, Munich, Germany, September 9-13, 2001

Kenzelmann, M.; Coldea, R.; Tennant, D. A.; Visser,D.; Hoffmann, M.; Smeibidl, P.; Tylczynski, Z.:Field dependence of magnetic ordering in thefrustrated XY magnet Cs2CoCl4ICNS 2001, Munich, Germany, September 9-13, 2001

Kikkinides, E. S.; Stefanopoulos, K. L.; Steriotis, Th.A.; Mitropoulos, A. Ch.; Kanellopoulos, N. K.; Treimer,W.:Combination of SANS and 3D stochasticreconstruction techniques for the study ofequilibrium and dynamic properties ofnanostructured materialsICNS 2001, Munich, Germany, September 9-13, 2001

Kirsch, R.; Beutler, O.; Funk, T.; Gierlings, M.;Gruyters, M.; Brewer, W.; Prandolini, M.J.; Riegel, D.:Magnetic coupling of dilute Fe probe atoms toVneighbors in AuV alloys studied by TDPADXII Int. Conf. On Hyperfine Interactions, ParkCity,UT/USA, 13. –17. 8. 2001

Kiselev, M.A.; Gutberlet, T.; Kisselev, A.M.; Gapienko,I.V.; Lombardo, D.; Janich, M.; Hauss, T.; Ollivon, M.;Lesieur, P.:Study of glass transition in DPPC/DMSO/watersystem at low temperaturesICNS 2001, Munich, Germany, September 9-13, 2001

Kiselev, M.A.; Janich, M.; Lesieur, P.; Hoell, A.;Oberdisse, J.; Pepy, J.; Kisselev, A.M.; Gapienko, I.V.;Gutberlet, T.; Aksenov, V.L.:DMPC vesicles and mixed DMPC/C12E8 micellesorientation in strong magnetic fieldsICNS 2001, Munich, Germany, September 9-13, 2001

Köbler, U.; Hoser, A.; Kawakami, M.:Beobachtung eines Bloch Exponent von 5/2 amAntiferromagneten MnF2 mit S=5/2 und axialerAustauschanisotropieDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Köbler, U.; Hoser, A.; Mueller, R.; Fischer, K.; Beyss,M.:The impact of fourth-order exchange interactionson spin dynamics, order parameters and criticalbehaviourICNS 2001, Munich, Germany, September 9-13, 2001

Kolaric, B.; Steuerle, U.; Grimm, G.; Jaeger, W.; v.Klitzing, R.:



271

Structuring of linear and branchedpolyelectrolytes in aqueous free-standing films„Tag der Chemie“, FU Berlin, 7.11.2001

Kolenda, M.; Balanda, M.; Hofmann, M.; Penc, B.;Szytula, A.:Magnetic structures of RPd2GeICNS 2001, Munich, Germany, September 9-13, 2001

Kolenda, M.; Hofmann, M.; Leciejewicz, J.; Penc, B.;Szytula, A.:Neutron diffraction studies of R5Rh4Ge10

(R=Tb,Ho,Er)ICNS 2001, Munich, Germany, September 9-13, 2001

Kolenda, M.; Penc, B.; Stüsser, N.; Szytula, A.;Zygmunt, A.:Magnetic order in RAuIn (R=Tb,Dy,Ho)compoundsICNS 2001, Munich, Germany, September 9-13, 2001

Kölln, K.; Müller, M.; Czihak, C.; Schober, H.;Nishiyama, Y.; Vogl, G.:All disordered regions of native cellulose are ofthe same nature?ICNS Munich, Germany, September 9-13, 2001

Kreyßig, A.; Dreyhaupt, A.; Krug, K.; Schedler, R.;Doerr, M.; Rotter, M.; Ritter, C.; Ressouche, E.;Grenier, B.; Prokes, K.; Winzer, K.; Loewenhaupt, M.:Characterisation of magnetic phases of DyNi2B2Cin an applied magnetic fieldICNS 2001, Munich, Germany, September 9-13, 2001

Krimmel, A.; Reehuis, M.; Loidl, A.:CF-effects and disorder versus Kondo latticebehavior in CeTSi3 (T=Rh, Ir)ICNS 2001, Munich, Germany, September 9-13, 2001

Krimmel, A.; Reehuis, M.; Loidl, A.:CEF-effects and disorder versus Kondo latticebehaviour in CeMSi3 (M = Rh, Ir)ICNS 2001, Munich, Germany, September 9-13, 2001

Krist, T.; Fritzsche, H.; Temst, K.; Mezei, F.:Large angle neutron polarisation analyserICNS 2001, Munich, Germany, September 9-13, 2001

Krist, Th.; Mezei, F.:Festkörper-Neutronenpolarisatoren undKollimatorenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Krist, Th.; Rupp, A.; Russina, R.; Mezei, F.:Broadband polarizers and neutron opticsWR-Audit zur Europäischen Spallationsquelle, Jülich,Germany, December 10, 2001

Lake, B.; Aeppli, G.; Lefmann, K.; McMorrow, D.F.;Christensen, N.B.; Clausen, K.N.; Rønnow, H.M.;Mangkorntong, M.; Hussey, N.E.; Sasagawa, T.;

Nohara, M.; Takagi, H.; Vorderwisch, P.; Smeibidl, P.;Mason, T.E.; Schröder, A.:Field-induced antiferromagnetism in a high-temperature superconductorICNS 2001, Munich, Germany, September 9-13, 2001

Lebedev, V.T.; Török ,Gy.; Cser,.L.; Kali, Gy.;Sibilev,.A.I.:Molecular dynamics of poly(N-vinylcaprolactam)hydrateICNS 2001, Munich, Germany, September 9-13, 2001

Lebedev, V.T; Török ,Gy.; Kirsh, Yu, E.; Kali,Gy.:SANS/NSE-study of poly(N-vinylcaprolactam) bycoil-globule transition4th Int. Discussion Meeting on Relaxation in ComplexSystems, Hersonissos, Crete, Greece, June 18-26,2001 (IDMRCS)

Lechner, R.E.:Quasielastic high-resolution direct geometry TOFspectrometers at steady-state reactors and atspallation sourcesICNS 2001, Munich, Germany, September 9-13, 2001

Lechner, R.E.; Hauß, T.:Hydration water and biological membranesESS-WR-Audit, FZ Jülich, 10th December 2001

Lechner, R.E.; Pappas, C.:Material transport phenomenaESS-WR-Audit, FZ Jülich, 10th December 2001

Lieutenant, K.; Fritzsche, H.; Mezei, F.:MC simulations of reflectometers at reactor andspallation sourcesICNS 2001, Munich, Germany, September 9-13, 2001

Lieutenant, K.; Gutberlet, T.; Wiedenmann, A.:MC simulations of SANS instruments for ESS7th ESS General Meeting, Seggau, Austria,September 26-29, 2001

Lo Celso, F.; Triolo, A.; Negroni, F.; Hainbuchner, M.;Baron, M.; Strunz, P.; Rauch, H.; Triolo, R.:Structural investigation on hybridnanocompositesICNS 2001, Munich, Germany, September 9-13, 2001

Lo Celso, F.; Triolo, F.; Triolo, A.; McClain, J.M.;deSimone, J.M.; Heenan, R.K.; Amenitsch, H.; Triolo,R.:Industrial applications of aggregation of blockcopolymers in superctritical Co2: a SANS studyICNS 2001, Munich, Germany, September 9-13, 2001

Lonkai, Th.; Hohlwein, D.; Ihringer, J.; Prandl, W.:Magnetische Ordnung in YMnO3 und HoMnO3

65. Physikertagung und Frühjahrstagung desArbeitskreises Festkörperphysik (AKF) der DPG,Hamburg, Germany, 03.26-30, 2001

Lonkai, Th.; Hohlwein, D.; Ihringer, J.; Prandl, W.:



272

Magnetische Ordnung in YMnO3 und HoMnO3: einkohärentes oder inkohärentes Problem?Deutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Loose, A.; Feyerherm, R.; Ishida, T.; Lawandy, M. A.;Li, J.:Crystal and magnetic structures of FePM2Cl2,Co(ox)(bpy) and MCl2(bpy), M = Co, Ni, determinedby neutron powder diffraction mid-termConference on the European Science FoundationProgramme ‘Molecular Magnets, Davos, Switzerland,March 10 - 15, 2001

Loose, A.; Wozniak, K.; Dominiak, P.; Sarin, V.A.;Smirnov, L.S.; Baranov, A.I.; Natkaniec, I.; Dolbinina,V.V.; Shuvalov, L.A.:Neutron and X-ray single crystal diffraction studyof [Rbx(NH4)1-x]3H(SO4)2, (T=290K, x 0.11)European Crystallographical Meeting, Krakow,Poland, August 25-31, 2001

Maksimov, I.; Litterst, F. J.; Feyerherm, R.; Mydosh,J. A.; Süllow, S.:Composition dependence of the magnetic andelectronic properties of UPd2-xSnSCES 2001 , Ann Arbor USA, August 2001

Mangin, S.; Montaigne, F.; Bellouard, C.; Chatelain,C.; Fritzsche, H.:Magnetic configuration at the interface of anexchange bias system studied by polarisedneutron reflectometryICNS 2001, Munich, Germany, September 9-13, 2001

Mastoraki, I.; Lappas, A.; Schneider, R.; Többens, D.;Giapintzakis, J.:Spin-gap and antiferromagnetic correlations inlow-dimensional PbNi2-xAxV2O8 (A= Mg, Co)compoundsICNS 2001, Munich, Germany, September 9-13, 2001

Matas, S.; Adams, E.D.; Batko, I.; Boyko, V.; Raasch,S.; Siemensmeyer, K.; Schöttl, S.; Sherline, T.E.:Neutron scattering experiment on solid 3He11th Czech and Slovak Conference on Magnetism,Kosice, Slovakia , 20-23. Aug. 2001

Matas, S.; Batko, I.; Boyko, V.; Radulov, I.; Schöttl,S.; Siemensmeyer, K.; Raasch, S.; Sherline, T.E.;Adams, E. D.:Instrument for a neutron scattering experiment onsolid 3HeICNS 2001, Munich, Germany, September 9-13, 2001

Matas, S.; Mihalik, M.; Reiffers, M.; Kacmarcikova, E.;Prokes, K.:Elastic neutron study of DyNi5 single crystal11th Czech and Slovak Conference on Magnetism,20-23. Aug. 2001 Kosice, Slovakia, (poster)

Meissner, M.; Smeibidl, P.:

Sample environment equipment at BENSC formagnetic fields up to 17 Tesla and temperaturesfrom 300 to 0.03 KelvinICNS 2001, Munich, Germany, September 9-13, 2001

Mergia, K.; Baczewski, L. T.; Hamada, S.; Gamari-Seale, H.; Hauschild, J.; Messoloras, S.; Shinjo, T.:Neutron reflectivity study of Gd/Cr multilayersICNS 2001, Munich, Germany, September 9-13, 2001

Meschke, M.; Siemensmeyer, K.:Frustationseffekte bei antiferromgnetischerOrdnung des Fxx-Gitters: K2IrCl6Deutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Migliardo, F.; Maisono, G.; Migliardo, P.:Characterisation of conformational properties ofprotein/trehalose/water system by neutronscatteringICNS Munich, Germany, September 9-13, 2001

Mihalik, M.; Matas, S.; Zentkova, M.; Arnold, Z.;Mikulina, O.; Rogl, P.:Investigation of the magnetic phase transition inU3Al2Si311th Czech and Slovak Conference on Magnetism,Kosice, Slovakia, 20-23. Aug. 2001

Mukherji, D.; Strunz, P.; Gilles, R.; Rösler, J.; Fuess,H.; Wiedenmann, A.:In-situ SANS investigation of precipitatemicrostructure at elevated temperatures in Re-rich Ni-base superalloyICNS 2001, Munich, Germany, September 9-13, 2001

Müller, R.; Hiergeist, R.; Gawalek, W.; Hoell, A.;Wiedenmann, A.:Magnetic and structural investigations on bariumhexaferrite ferrofluids9th Int. Conference on Magnetic Fluids (ICMF9),Bremen, Germany, 23. – 27.7.2001

Nakotte, H.; Chang, S.; Klaasse, J.C.P.; Brück, E.; deBoer, F.R.; Prokes, K.; Mihalik, M.:High fields magnetization in single-crystallineUIrGePhysical Phenomena at high magnetic fields – IV,Santa Fe, 20.10.2001

Neov, S.; Dabrowski, L.; Hofmann, M.; Bouwmeester,H.:Neutron diffraction and mössbauer spectroscopystudy of La0.6Sr0.4Fe1-xCoxO3-y (x = 0, 0.5)perovskitesICNS 2001, Munich, Germany, September 9-13, 2001

Neov, S.; Marinova, V.; Reehuis, M.; Sonntag, R.:Neutron diffraction study of Bi12MO20 singlecrystals with sillenite structure, (M = Si,Si0.995Mn0.005, Bi0.53Mn0.47)ICNS 2001, Munich, Germany, September 9-13, 2001



273

Oeser, R.; Rieutourd, F.; Menzel, H.; Schnitter, M.;Steitz, R.; Luap, C.; Siebrecht, R.; Cubitt, R.:Structure and stability of polyion-complexedLanguir-Blodgett filmsICNS 2001, Munich, Germany, September 9-13, 2001

Ono, M.; Habicht, K.; Keller,T.:Larmor precession neutron diffraction techniquefor high precision determination of strain ineutectic single crystal composite Al2O3/Y3Al5O12

(YAG)ICNS 2001, Munich, Germany, September 9-13, 2001

Ono, T.; Tanaka, H.; Kato, T.; Hoser, A.; Stüßer, N.;Schotte, U.:Spin strucuture of CsCu1-xCoxCl3 in the magneticfieldICNS 2001, Munich, Germany, September 9-13, 2001

Padureanu, I.; Lechner, R.E.; Aranghel, D.;Radulescu, A.; Desmedt, A.; Pieper, J.:Temperature dependence of the dynamicscattering function in glycerol studied by quasi-elastic slow neutron scatteringICNS 2001, Munich, Germany, September 9-13, 2001

Pappas, C.; Mezei, F.:How to achieve high intensity in NSEspectroscopy?Millenium Workshop , ILL, Grenoble, France, April 6-7, 2001,

Pappas, C.; Mezei, F.; Ehlers, G.; Campbell, I.A.:Dynamic scaling in spin glasses: neutron spinecho results and theoryFourth Int. Discussion Meeting on Relaxations inComplex Systems, Heraklion, Greece, 18-26.6.2001

Pappas, C.; Mezei, F.; Ehlers, G.; Campbell, I.A.:Relaxation in spin glasses; comparison of of NSEresults with theoryDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Pappas, C.; Triolo, A.; Kischnik, R.; Mezei, F.:Wide Angle NSE and TOF: the spectrometerSPAN at BENSCICNS 2001, Munich, Germany, September 9-13, 2001

Petrenko, O.A.; Balakrishnan, G.; McK Paul, D.;Yethiraj, M.; Klenke, J.:Field induced transitions in the highly frustratedmagnet Gadolinium Gallium Garnet - long or shortrange order?ICNS 2001, Munich, Germany, September 9-13, 2001

Pieper, J.; Irrgang, K.-D.; Renger, G.; Lechner, R.E.:Density of phonon states in the light-harvestingcomplex II of green plantsICNS 2001, Munich, Germany, September 9-13, 2001

Pirogov, A.; Park, J.; Park, J. -G.; Lee, C.H.; Prokes,K.; Valiev, E.; Kudrevatykh, N.; Sheptyakov, D.:

Neutron diffraction investigation of the spin-reorientation transition in Tm2Fe17


Prokes, K.; Nakotte, H.; Brück, E.; de Châtel, P.F.;Sechovsky, V.:Field-induced magnetic structures in UNiGe31iemes Journèes des Actinides, Saint-Malo, 27.4.2001

Prokes, K.; Nakotte, H.; Svoboda, P.; Sechovsky, V.;Robinson, R.A.:Magnetism in UTGe (T = transition metal)compounds probed by neutron diffractionDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Prokes, K.; Nakotte, H.; Brück, E.; de Châtel, P.F.;Sechovsky, V.:Field-induced magnetic structures in UNiGeICNS 2001, Munich, Germany, September 9-13, 2001

Prokes, K.; Smeibidl, P.; Meissner, M.:Neutron scattering in magnetic fields up to 17 TPhysical Phenomena at High Magnetic Fields – IV,Santa Fe, 22.10.2001

Pyzalla, A.; Mayer, H.M.; Reimers, W.; Pintchovius,L.; Brockmeier, H.:The new material science diffractometer at theneutron source FRM IIICNS 2001, Munich, Germany, September 9-13, 2001

Py za lla , A .; Wa ng, L .; Wild, E.; W ro ble wsk i, T.:Mikrostruk tu elle V eränd eru ng en auf d er Obe rfläc hevo n Sch ien en HA SY LAB -Us er Me eting , H amb urg, 26.01 .20 01

Pyzalla, A.; Wegener, J.; Lima, E.; Jacques, J.P.;Feiereisen, T.; Buslaps, T.:Residual stress and in-situ strain analysis usingwhite high energy synchrotron radiationUser – Meeting, ESRF, Grenoble, France, 19.02.2001

Radulescu, A.; Lechner, R.E.; Padureanu, I.;Postolache, C.:Additional low-frequency modes in zirconiumhybridesICNS 2001, Munich, Germany, September 9-13, 2001

Recko, K.; Szymanski, K.; Dobrzynski, L.;Waliszewski, J.; Biernacka, M.; Satula, D.;Perzynska, K.; Suski, W.; Wochowaski, K.; André, G.;Bourée, F.; Hoser, A.:Magnetism of UFe4-xAl8+x (x = <-0.4, 0.4>)intermetallics4th Int. Conference on F-Elements, Madrid, Sept 17-21, 2001

Reehuis, M.; Loose, A.; Sarin, V.; Smirnov, L.;Natkaniec, I.; Baranov, A.; Dolbinia, V.; Shuvalov, L.:Phase transition II-III study in of (NH4)3H(SO4)2 byneutron scattering



274


Reehuis, M.; Pohlkamp, M.; Jeitschko, W.; Ouladdiaf,B.; Hofmann, M.:Magnetic structure of the ternary carbide HoMoC2

and ErMoC2


Ribeiro, P.A.; Raposo, M.; Haas, H.; Steitz, R.:Study of a Poly(ethylenimine) layer as layer-by-layer films precursorChains @ Interfaces 2001, A EuroConference on thePhysics of Surfactants and Polymers at Interfaces,Évora, Portugal, January 14th to 19th, 2001

Roennow, H.M.; Enderle, M.; McMorrow, D.F.;Regnault, L-P.; et al.:Structure and excitations in the high-field solionphase of CuGeO3


Rogalski, O.; Vorderwisch, P.; Hüller, A.:Zur Temperaturabhängigkeit der Linienbreitenvon freien quantenmechanischen RotatorenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Rotter, M.; Kramp, S.; Loewenhaupt, M.; Gratz, E.;Schmidt, W.; Pyka, N.M.; Hennion, B.:Magnetic excitations in the antiferromagneticphase of NdCu2


Rousseau, D.; Marty, J.-D.; Mauzac, M.; Martinoty, P.;Brandt, A.; Guenet, J.-M.:Conformation of a side-chain liquid crystalpolymer in solutionICNS 2001, Munich, Germany, September 9-13, 2001

Rousseau, D.; Marty, J.-D.; Mauzac, M.; Martinoty, P.;Brandt, A.; Guenet, J.-M.:Conformation en solution d’un polymère cristal-liquide à châines latérales10ème Colloque Francophone sur les CristauxLiquides, Toulouse, September 18-21, 2001

Russina, O.; Russina, M.; Mezei, F.; Lechner, R.E.;Pieper, J.; Desmedt, A. ; Dreyfus, C.:Dynamic correlations around the glass transitionin systems with different degrees of fragilityICNS 2001, Munich, Germany, September 9-13, 2001

Schmitz, D.; Hauschild, J.; Liu, Y. T.; Fritzsche, H.;Maletta, H.:XMCD and polarized neutron reflectometry ofultrathin Fe on a V(110) single crystalBessy User Meeting, 6. – 7. 12. 2001, Bessy –Adlershof

Schneider, R.; Chatterji, T.; Hoffmann, J.-U.;Hohlwein, D.:RKKY-like interactions in the paramagnetic phaseof holmium


Schneider, R.; Hoffmann, J.-U.; Hohlwein, D.:TVtueb – Visusalisierung und Auswertungzweidimensionaler Diffraktionsdaten – Analysediffuser StreuintensitätenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Schneider, R.; Pyzalla, A.:Determination of stress and strain by neutrondiffractionESS – Workshop, Forschungszentrum Jülich, Jülich,10.12.2001

Schneider, R.P.; Chatterji, T.; Hoffmann, J.-U.;Hohlwein, D.:Magnetic diffuse scattering in TbICNS 2001, Munich, Germany, September 9-13, 2001

Schöttl, S.; Siemensmeyer, K.; Boyko, V.; Batko, I.;Matas, S.; Raasch, S.; Adams, E. D. ; Sherline, T.E.:Neutron Scattering Experiment on Solid 3HeICNS 2001, Munich, Germany, September 9-13, 2001

Schöttl, S.; Siemensmeyer, K.; Boyko, V.; Bat’ko, I.;Matas, S.; Adams, E.D.; Sherline, T.E.:Neutronenstreuexperiment an festem 3HeFrühjahrstagung der Deutschen PhysikalischenGesellschaft, 23. – 31.03.2001, Hamburg

Schöttl, S.; Siemensmeyer, K.; Boyko, V.; Bat’ko, I.;Matas, S.; Adams, E.D.; Sherline, T.E.:Neutronenstreuexperiment an festem 3HeDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Schöttl, S.; Siemensmeyer, K.; Boyko, V.; Batko, I.;Matas, S.; Raasch, S.; Adams, E. D.; Sherline, T.E.:Neutron scattering sxperiment on solid 3HeJournal of Low Temperature Physics, QFS 2001,Konstanz, Germany, 22.-27 July, 2001

Schukow, H.; Breitinger, D.K.; Schneider, R.; Mohr,J.; Schwab, R.G.:Galloalunite – a neutron diffraction studyICNS 2001, Munich, Germany, September 9-13, 2001

Smeibidl, P.; Kausche, S.; Meißner, M.:Neutron scattering at high magnetic fileds andlow temperaturesICNS 2001, Munich, Germany, September 9-13, 2001

Stanzick, H.; Banhart, J.; Klenke, J.; Danilkin, D.:Metal foam evolution and decay studied byneutron radioscopyICNS 2001, Munich, Germany, September 9-13, 2001

Stanzick, H.; Banhart, J.; Helfen, L.; Baumbach, T.;Klenke, J.:Metal foam evolution studied by X-ray andneutron radioscopy



275

2nd Int. Conference on Cellular Metals and MetalFoaming Technology (MetFoam2001), Bremen,Germany, 18.-20 Juni 2001

Steriotis, Th. A.; Stefanopoulos, K. L.; Mitropoulos, A.Ch.; Kanellopoulos, N. K.; Hoser, A.; Hofmann, M.:Structural studies of supercritical CO2 in confinedspaceICNS 2001, Munich, Germany, September 9-13, 2001

Strobl, M., Treimer, W., Hilger, A.:Advancement on the development of USANS fornon destructive material investigationsInt. Conf. on Nuclear and Radiation Physics, Almaty,Kassachstan, 4. - 7. Juni 2001

Strobl, M.; Treimer, W.:Channel cut crystals mit beeinflußbarenReflexionskurvenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Strunz, P.; Schumacher, G.; Mukherji, D.; Gilles, R.;Zrník, J.; Wiedenmann, A.:SANS examination of precipitate microstructure inNi-base superalloysICNS 2001, Munich, Germany, September 9-13, 2001

Strunz, P.; Zrnik, J.; Wiedenmann, A.:Small-angle neutron scattering investigation ofmicrostructural changes in long-time thermalexposed Ni-base superalloy EI698VDEUROMAT 2001, Rimini, Italy, 10.06.-14.06.2001

Stuhr, U.; Vorderwisch, P.; Kokorin, V.V.:Phonon softening preceding the forward andreverse martensitic transformation in Ni2MnGaICNS 2001, Munich, Germany, September 9-13, 2001

Stüßer, N.; Hofmann, M.:Impulsraumfokussierung durch Verwendungeines in-pile Fächerkollimators in Verbindung miteinem horizontal gekrümmten MonochromatorDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Stüßer, N.; Hofmann, M.:A neutron diffractometer with an adjustable in-pilefan collimator for focusing in reciprocal and realspaceICNS 2001, Munich, Germany, September 9-13, 2001

Svoboda, P.; Vejpravova, J.; Rotter, M.; Doerr, M.;Loewenhaupt, M.; Hofmann, M.; Schneider, R.:Complex magnetic phase diagram of TmCu2


Syshchenko, O.; Sechovsky, V.; Prokes, K.;Hofmann, M.:Magnetic structures of Er6Ni2SnICNS 2001, Munich, Germany, September 9-13, 2001

Szytula, A.; Bazela, W.; Gondek, L.; Stüsser, N.;Zygmunt, A.; Penc, B.:Magnetic structures and magnetic phasetransition in RAuInXII School of Modern Physics, Ladek Zdrój, June 21-24, 2001

Tanaka, H.; Oosawa, A; Kato, T.; Kakurai, K.; Hoser,A.:Neutron scattering study of the field-inducedphase transition in the spin gap system TlCuCl3ICNS Munich, Germany, September 9-13, 2001

Temst, K.; Van Bael, M. J.; Fritzsche, H.:Off-specular polarized neutron reflectometrystudy of magnetic dots with a strong shapeanisotropyICNS 2001, Munich, Germany, September 9-13, 2001

Theissmann, R.; Ehrenberg, H.; Weitzel, H.; Fuess,H.:Influence of the real strucuture on the magneticproperties of FeNbO4


Többens, D.; Tovar, M.:Erste Experimente mit dem neuen vertikalfokussierenden Monochromator am E9Deutsche Gesellschaft für Kristallographie,Jahrestagung in Bayreuth, 12.-15.03.2001

Többens; D. M.; Tovar, M.:Erste Experimente mit dem neuen vertikalfokussierenden Monochromator am E99. Jahrestagung der Deutschen KristallographischenGesellschaft, Bayreuth, 12.-15. März 2001

Többens; D. M.; Tovar; M.:Peak shape at the axially focusing E9 powderdiffractometer - theoretical and experimentaldescriptionICNS 2001, Munich, Germany, September 9-13, 2001

Toda, M.; Fuji, Y.; Kawano, S.; Goto, T.; Chiba, M.;Ueda, S.; Klenke, J.; Graf , H. A.; Steiner, M.:“Neutron diffraction study of the field inducedorder in singlet-ground-state magnet CsFeCl3 ”Yukawa-Institute-for-Theoretical-Physics Int.Workshop, „Order, Disorder, and Dynamics inQuantum Spin Systems'' Kyoto-Kaikan, Sakyo-ku,Kyoto, November 15-16, 2001

Tomuta, D. G.; Nieuwenhuys, G. J.; Feyerherm, R.;Mydosh, J. A.:Magnetic alignment of the RE sublattice inReMnO3


Török , Gy.; Lebedev, V.T.; Bershtein, V.A.; Zgonnik,V.N.:Neutron study of fullerene-containing polymers



276

4th Int. Discussion Meeting on Relaxation in ComplexSystems , Hersonissos, Crete, Greece, June 18-26,2001 (IDMRCS)

Török, Gy.; Lebedev, V.T.; Cser, L.; Zrínyi, M.;Buyanov, A.L.:Transport of magnetic particles in ferrogels byneutron scatteringInt. Conference on Magnetic Fluids (ICMF9), Bremen,Germany, July 23-27, 2001

Tovar, M.; Többens, D.:Low temperature structural properties of CuCr2O4

investigated by neutron powder diffractionDeutsche Gesellschaft für Kristallographie,Jahrestagung in Bayreuth, 12.-15.03.2001

Tovar, M.; Többens, D.M.:Jahn-Teller oxide spinels investigated by neutronpowder diffractionICNS 2001, Munich, Germany, September 9-13, 2001

Treimer, W.; Strobl, M.; Hilger, A.; Seifert, C.:Thermal neutron optical experiments with a highresolution double crystal diffractometerICNS 2001, Munich, Germany, September 9-13, 2001

Treimer, W.; Strobl, M.; Hilger, A.:Experiments with tuneable many bounce channelcut crystals for thermal neutron scattering2nd Int. Conf. Of the European Society for PrecisionEngineering and Nanotechnology (EUSPEN), Turin,27th - 31. May 2001

Triolo, A.; Lo Celso, F.; Arrighi, V.; Lechner, R.E.;Triolo, A.:Segmental dynamics in polymer electrolytesICNS 2001, Munich, Germany, September 9-13, 2001

Triolo, A.; Negroni, F.; Arrighi, V.; Lechner, R.E.; LoCelso, F.; Teriolo, R.:Quens investigation of filled rubberICNS 2001, Munich, Germany, September 9-13, 2001

Triolo, A.; Pappas, C.; Arrighi, V.:NSE and TOF investigation of coherent dynamicsof atactic polypropyleneICNS 2001, Munich, Germany, September 9-13, 2001

Ulbricht, A.; Böhmert, J.; Strunz, P.; Dewhurst, C.;Mathon, M.-H.:Structure investigations on russian reactorpressure vessel steels by small angle neutronscatteringICNS 2001, Munich, Germany, September 9-13, 2001

Ulbricht, A.; Böhmert, J.; Strunz, P.; Dewhurst, C.;Mathon, M.-H.:Strukturuntersuchungen an bestrahltenrussischen Reaktordruckbehälterstählen mitNeutronenkleinwinkelstreuungDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Ulrich, C.; Khaliullin, G.; He, H.; Reehuis, M.; Ohl, M.;Ivanov, A.; Taguchi, Y.; Tokura, Y.; Keimer, B.:Spin order and orbital degrees of freedom in YVO3

and LaVO3


v. Klitzing, R.; Jaeger, W.; Steitz, R.:Influence of charge densitiy on the formation ofpolyelectrolyte multilayerHauptversammlung der Kolloidgesellschaft, Potsdam,Germany, 24.9.-26.9.2001

v. Klitzing, R.; Steitz, R.; Tauer, K.; Khrenov, V.:Ultrathin polymer films of chargedthermosensitive blockopolymersDPG Tagung, Berlin, 2.4.-6.4.2001

Watanabe, J.; Smirnov, L.S.; Natkaniec, I.; Balagurov,A.M.; Beskrovnyi, A.I.; Kasahara, M.; Yagi, T.:Neutron and raman scattering studies of[K1-x(NH4)x]3H(SO4)2 mixed crystalsICNS 2001, Munich, Germany, September 9-13, 2001

Watanabe, J.; Smirnov, L.S.; Natkaniec, I.; Kubanek,F.; Kasahara, M.; Yagi, T.:Raman, neutron and X-ray scattering studies of[K1-x(NH4)x]3H(SO4)2 mixed crystalsXIV Conference-Workshop "Horizons in HydrogenBond Research", Torino, Esposizioni, Torino-Italy,September 3-7 2001

Wegener, J.; Pyzalla, A.; Müller, K.B.:Direct and indirect extrusion of the two-phasealloy AlSi25Cu4Mg1Materials Week, München, 24.09.-28.09.2001

Wesemann, A.; Ahrens, H.; Steitz, R.; Estrella-Lopez,I.; Förster, S.; Helm, C.A.:PEE-PEO diblockcopolymer monolayers at thewater surfaceFrühjahrstagung der Deutschen PhysikalischenGesellschaft (Fachverband Chemische Physik),Berlin, 2.-6. April 2001

Wesemann, A.; Ahrens, H.; Steitz, R.; Papastavrou,G.; Helm, C.A.:Lateral self-organization at fluid interfaces: inter-and intramolecular interactionsVorbereitungstreffen zum Gutachterkolloquium desSchwerpunktprogramms „Benetzung“, 18.-20.Juli,2001

Wesemann, A.; Ahrens, H.; Steitz, R.; Papastavrou,G.; Helm, C.A.:Lateral self-organization at fluid interfaces: inter-and intramolecular interactionsGutachterkolloquium des Schwerpunktprogramms„Benetzung“, 7.- 9. November 2001

Wiedenmann, A.:Polarized neutrons used in SANS investigationsof magnetic nanomaterials



277


Wiedenmann, A.:Nanomaterials analysed by polarized SANSESS Instrumentation, Jülich, 10.12.2001

Wiedenmann, A.:Nanomaterials analyzed by polarisedSANS, Meeting European Spallation Source(Ess),Jülich, 10.12.2001

Wiedenmann, A.; Hoell, A.:Untersuchung von Kern und Hülle in Cobalt-Ferrofluiden durch Kleinwinkelstreuung mitpolarisierten NeutronenDeutsche Neutronenstreutagung 2001, Jülich,Germany, 19.- 21.2. 2001

Wiedenmann, A.; Hoell, A.:Small angle neutron scattering investigations onferrofluids using polarized neutronsISMANAM, Int. Symposium, Ann Arbor, Michigan,USA, 24. – 29.06.2001

Wiedenmann, A.; Kammel, M.; Hoell, A.:Untersuchung von Kern und Hülle in Magnetit-Ferrofluiden durch Neutronen-KleinwinkelstreuungDeutsche Neutronenstreutagung, Jülich, 19. -21.2.2001.

Willumeit, R.; Förster, F.; Funari, S.; Hauß, T.; Hubo,S.; Kruse, M.; Andrä, J.:The interaction of the synthetic peptide NK2 withmodel membranesICNS 2001, Munich, Germany, September 9-13, 2001

Wilmer, D.; Feldmann, H.; Combet, J.; Lechner, R.E.:Anion and cation dynamics in ion conductingsulfates and phosphatesICNS 2001, Munich, Germany, September 9-13, 2001

Wolter, A.; Mienert, D.; Klauss, H. H.; Litterst, F. J.;Feyerherm, R.; Kubaner, F.; Geibel, C.; Süllow, S.:Structure and magnetic order in Co2NbSnDPG - Tagung, Hamburg, March 2001

Yermakov, A.A.; Schneider, R.; Baranov, N.V.:Effect of magnetic field on the initerant Co-subsystem in Ho0.423Y0.577Co2


Zrnik, J.; Strunz, P.; Hornák, P.; Wiedenmann, A.;Vrchovinsky, V.:Microstructural changes in long-time thermallyexposed Ni-base superalloy studied by SANSICNS 2001, Munich, Germany, September 9-13, 2001

Zsigmond, G.; Lieutenant, K.; Manoshin, S.; Mezei,F.:VITESS simulation of backscattering andreflectometry at spallation sourcesInt. Workshop on New Opportunities in Single CrystalSpectroscopy with Neutrons, Balaton, Hungary, April19-22, 2001

Zsigmond, G.; Lieutenant, K.; Mezei, F.:MC simulation of single crystal spectroscopy anddiffraction at spallation sourcesICNS 2001, Munich, Germany, September 9-13, 2001

Zsigmond, G.; Lieutenant, K.; Peters, J.; Jauch, W.;Mezei, F.:Instrument development software for ESSWR-Audit for ESS, Jülich, Germany, December 10-11, 2001


Theses

Examina (Diplom- und Doktorarbeiten)

278

Diploma

Annibali, A.:Studio dello stato tensionale residuo indotto datrattamenti termochimici superficiali sucomponenti sinterizzati tramite tecniche didiffrazione neutronica (Study of the stress stateinduced by thermochemical surface treatmentsin sintered components by means od neutrondiffraction techniques)Graduation Thesis, Faculty of MechanicalEngineering, University of Ancona (Italy), March2001

Crapanzano , L.:Caratterizzazione strutturale di copolimeri ablocchi in soluzione (diploma)University of Palermo, October 2001

Rüegg, Ch.:Neutron scattering investigations of the S=1/2quantum spin systems TlCuCl3 and NH4CuCl3ETH Zürich, Febr. 2001

Doktorarbeiten

Cavadini, N.:Investigation of Magnetic Correlations inQuantum Spin Systems by Neutron ScatteringExperimentsETH Zurich, Switzerland, September, 2001

Charalambopoulou, G. Ch.:Characterisation of the structure of porousmedia and its effect on mass transfer, withapplication in therapeutic controlled releasesystemsDepart. of Chemical Engineering, NationalTechnical University of Athens, March 2001

Cho, S.-J.:Ellipsometrische Untersuchungen anVielschichtsystemenTU Berlin, Juli 2001

Haarmann, F.:Alkalimetallhydrogensulfide Struktur undDynamik: Eine Untersuchung imTemperaturbereich von 4 K T 520K mitelastischer und quasielastischerNeutronenstreuung sowie Festkörper NMR-SpektroskopieUniv. Dortmund, Jan. 2001

Heinemann, A.:Modell für die Kleinwinkelstreuung undAnwendungenTU Dresden, Oktober 2001

Hernandez-Velasco, J.:Nuevos Óxidos R2BaCoO5 (R=Tierra Rara):Síntesis y Transiciones de Fase Estructurales yMagnéticasUniversidad Complutense de Madrid, December2001

Kaisermayr, M.:Neutron Scattering Study of Diffusion in theIntermetallic B2 Phases NiGa and CoGa (PhDthesis)Universität Wien, July 2001

Kreyßig, A.:Einfluß der magnetischen Ordnung aufSupraleitung und Kristallstruktur in Seltenerd-Nickel-Borkarbid-VerbindungenTU Dresden, 2001

Meschke, M.:Feldinduzierter Phasenübergang im kubischenAntiferromagneten K2IrCl6TU Berlin, März 2001

Schneider, R.:Neutronenuntersuchungen an den anisotropenAntiferromagneten CsNiCl3, Holmium undKupfertetraminsulfatUniversität Tübingen, Mai 2001

Sellmann, R.:Spin-Reorientierungsübergang ultradünnerepitaktischer Kobalt-SchichtenTU Berlin, Januar 2001

Wegener , J.:Mikrost ru ktu r, Text ur un d Eig enspannu ng en vo nst rangg ep resst en un d reibrü hr-geschweiß ten au sh ärt baren A lumin iumlegieru ngenTU Berl in, Septem ber 2001


Theses

Examina (Diplom- und Doktorarbeiten)

279

Habilitation

Prokes, K.:Magnetic Structures and related physicalproperties of f electron systemsCharles University, Prague, 2001

Pyzalla, A.:An alyse stark plast isch verfo rmt er Werksto ff e mit Beug ung sverf ah ren Ruhr -Universität Bochum, Juli 2001

AUTHOR INDEX

author page author page author page

280

AAbrahamsen A.B. 5Aeppli G. 70, 71Afanasiev M.L. 97Agosti E. 194Ahrens H. 146Aliotta F. 120Amoretti G. 78Andersen N.H. 26, 69Andrä J. 153, 154Andreev A.V. 35Anzur C. 107, 108Aranghel D.F. 118Arialdi G. 124Arrighi V. 124, 125, 126Aruga Katori H. 29Aso N. 28Auffermann G. 102

BBaglioni P. 152, 165Baiata V. 122Balog E. 160Banhart J. 211Baran S. 52, 53Basler R. 85Batdemberel G. 172, 174Bayrakci S. 36Behar M. 212Beirne E. 109Bentall M. 3Bernhoeft N. 84Berti D. 152, 165Bickulova N. 96Boothroyd A.T. 33Bourdarot F. 78Bouwman W.G. 166Bowers J. 151Bradshaw J.P. 155, 156Branca C. 139Brandt A. 133, 144Bremer M.G.E.G. 166Broholm C. 80Brück E. 196Bruno G. 175, 176, 177Buschow K.H.J. 68

CCaciuffo R. 78Cadogan J. 194Calandrini V. 127, 128Campbell S.J. 47, 57Cavadini N. 75, 83Cavagnat D. 117Chaboussant G. 85Charalampopoulou G. 171Chatterji T. 24, 25Cho S.-J. 233Christensen N.B. 69, 70, 71Coldea R. 81, 82Cosgrove T. 137Cowley R. 3

Czeslik K. 168

DDahint R. 141, 142Danilkin S. 1, 96, 185,

186, 207, 211Dante S. 157, 158, 170Davies S. 155, 156Deen P. 4Del Genovese D. 188, 190Dencher N.A. 158Deppe M. 16, 17Deriu A. 127, 128Desmedt A. 114, 115,

116, 117,119, 125,129, 160,161, 162

Dilthey U. 176Dominiak P. 98Donath E. 134Doster W. 159

EEfimova J. 166Ehrenberg H. 58Enderle M. 73, 76Estrela-Lopis I. 134, 169

FFak B. 78Falkenberg S. 182Falkenhagen S. 183Faraone A. 139Felcher G. 218, 219Feldmann H. 113FérnandezSerrano R.

175

Feyerherm R. 41, 61, 62,63, 66

Findenegg G.H. 147, 148Fink D. 212Fischer R. 163Fitzsimmons M. 225Flachbart K. 56Flerov I.N. 97Förster F. 153Frank J. 157Fratini E. 152Frick B. 129Fritzsche H. 88, 89, 90,

91, 92, 93,95, 216, 232

Fromme P. 157Fuess H. 174Fujii Y. 72

GGarcia-Matres E. 28, 32, 48, 67Gardiner C.H. 33Gavriljuk V. 185, 186Gay-Duchosal M. 112Gerbish S. 172Giapintzakis J. 12Gierlings M. 95Gilles R. 187, 188,

189, 190,221, 224

Girardin E. 177, 178, 179Giuliani A. 178Glavatska N. 185, 186Goff J. 4Golosovsky I. 64Golub R. 111Gondek L. 46Gonzalez-Doncel G. 175Gorev M.V. 97Gorzel A. 213, 214, 215Gournis D. 103Gräbner D. 136Gradzielski M. 135Graf H.A. 72Gratz E. 42, 50, 84,

107, 108Grimm H. 161Grunze M. 141, 142Gruyters M. 95Gubbens P.C.M. 44Güdel H.-U. 85Guenet J.-M. 133Guillaume F. 115, 116, 117Günther D. 56Gutberlet Th. 130, 131,

157, 168,169, 170

HHabicht K. 76, 79, 81,

82, 83, 109,111, 180, 220

Hahn H. 203, 204Harjo S. 206Harroun T. 155, 156Hauschild J. 93, 94Hauss Th. 130, 155,

156, 157,158, 159,170, 171

Hayashi T. 141, 142Heinemann A. 86, 194, 202Helm C.A. 146Hendrikx R. 62Hense K. 107, 108Hernandez-Velasco J.

48, 52, 54,55, 74

Hilger A. 60, 227, 228,229, 230, 231

AUTHOR INDEX


281

Hoell A. 86, 131, 134,137, 138,163, 164,167, 193,194, 196,197, 198,199, 200,201, 202

Hoffmann B. 135Hoffmann J. 233Hoffmann J.-U. 12, 20, 21Hofmann M. 40, 47, 57Hohlwein D. 7, 8, 9, 16,

17, 20, 21,22, 23, 96,

97, 185, 186Hoinkis E. 209Holmes P. 126Hölzel M. 207Hornak P. 192Hoser A. 6, 42, 49, 50,

107, 108Hossain Z. 17Hubo S. 153

IIrrgang K.D. 162Ishida T. 66

JJackler G. 168Janssen J. 43Janssen Y. 1Javorsky P. 44, 51Jeitschko W. 59

KKaisermayr M. 106Kammel M. 197, 198,

200, 202Katsaras J. 130Katsumata K. 29Kausche S. 5, 26, 80, 83Kawano S. 72Keiderling U. 135, 136,

144, 165,166, 203, 204

Keimer B. 36, 37, 38,79, 111

Keller Th. 79, 111, 180,218, 219, 220

Kemnitz E. 100Keshaw J. 222Kiselev M. 131Klenke J. 1, 2, 72, 211,

213, 215, 216Klösgen B. 169Kniep R. 102Knorr K. 101Köbler U. 49Kolomiyets O. 51Kretschmer M. 176Kreysig A. 39, 86

Krimmel A. 14, 15, 19, 59Krimmer B. 221, 224Krist T. 232, 233Kruse M. 153Krustev R. 151

LLake B. 69, 70, 71Lappas A. 12, 74, 103Lassegues J.C. 117Lebedev V.T. 150Lechner R.E. 84, 116, 117,

118, 119,127, 128,129, 159,161, 162

Leciejewicz J. 52, 53Lefmann K. 70Len A. 150Lentz G. 101Leporatti S. 134Liang B. 36Lo Celso F. 121, 123, 132Lohstroh W. 3, 87Loidl A. 59Lonkai Th. 7, 8, 9Loose A. 66, 100Lukas P. 191Lukowski G. 163

MMagazù S. 164Magerl A. 129Major J. 218, 219, 225Maksimov I. 41Maletta H. 94Manescu A. 177, 178, 179Mangin S. 91, 92Mangione S. 139Manson J.L. 66Markocsan N. 179Markosyan A.S. 42Martin D. 140Martinoty P. 133Marty J.-D. 133Mastoraki I. 12Matas S. 56Mauzac M. 133McEwen K.A. 109McMorrow D.F. 70, 71Meissner M. 56, 83Mergia K. 223Messoloras S. 223Meyer M. 136Mezei F. 111, 119Migliardo F. 164Mitsuda S. 30, 31Modigell M. 181Mogilny G. 186Montaigne F. 91, 92Montermann G. 221, 224Morreale V. 122

Moshopoulou E. 32, 48Motohashi Y. 206Moukarika A. 103Moze O. 194Mukherjee C.J. 81Mukherji D. 187, 188,

189, 190Mulders A. 44Müller M. 212Müller R. 199

NNelson A. 137Neov D. 191Nieuwenhuys G.J. 61, 63Niewa R. 102Nordskog A. 144Norgaard Toft K. 5, 26Novak V. 191Nugent N. 137Nuttall C.J. 74

OOchsenbein S. 85Oettl M. 160Oetzmann K. 153, 154Offerman S.E. 195Ohl M. 37Okano H. 30Ollivier J. 84, 112Ono M. 180Onori G. 127, 128

PPadureanu I. 118Pape L. 181Pappas C. 106, 126,

139, 140Pebler J. 14, 15Penc B. 45, 46, 52,

53, 54, 55Peschke H.J. 227Peters J. 60Petrenko O. 2, 27Pham T.D. 196Pieper J. 112, 118,

119, 122,127, 128,

129, 160, 162Platz G. 135Polarz S. 138Ponterio R. 120Powell D.H. 112Prager M. 114Prandl W. 7, 8, 9, 22Prandolini M.J. 95Prange W. 143Press W. 143Prokes K. 28, 29, 30,

31, 32, 34,35, 68, 73

Prots Y. 102Przenioslo R. 13

AUTHOR INDEX


282

Pynn R. 225

QQian H. 125Querol-Suquia A. 151

RRaasch S. 66Radulescu A. 118Rainford B.D. 84Rakhecha V.C. 226Raposo M. 149Reehuis M. 37, 38, 59,

100Regulski M. 13Rekveldt M.Th. 220, 225Renger G. 162Ribeiro P.A. 149Riegel D. 95Roennow H.M. 27, 69, 71, 76Rösler J. 189Rößler U.K. 39, 86Rousseau D. 133Rüegg Ch. 75, 83Rupp A. 213, 214, 215Russina M. 119Russina O. 119Ryukhtin V. 206

SSaggio F. 124, 126Saija F. 120Salevris A. 223Sangaa D. 58, 172, 174Santini P. 78Sarin V. 98Saroun J. 206Sarrao J.L. 32Schedler R. 10Schemmel S. 147, 148Schmahl, W.W. 182, 183, 184Schmitz D. 94Schneider R. 12, 13, 16,

20, 21, 24,25, 96, 185,

221, 224Schneidewind A. 10Schorr S. 104Schotte U. 6Schumacher G. 205Schwendel D. 141, 142Sechovsky V. 51Seydel J. 203, 204Siemensmeyer K. 56Sietsma J. 195Sitepu H. 182, 183, 184Sittner P. 191Skomorokhov A. 96, 185Smarsly B. 138Smeibidl P. 2, 5, 16, 17,

26, 30, 66,75, 76, 80,

81, 82

Smirnov L. 98Smith J.C. 160Soarez M.F. 212Soetens J.C. 116Sokolov A. 161Sosnowska I. 13Stanzick H. 211Steiner M. 72Steitz R. 143, 145,

147, 148,151, 168,169, 170

Steriotis Th.A. 171Stockert O. 16, 17Stone M.B. 80Strobl M. 227, 228,

229, 230, 231Strunz P. 134, 181,

187, 188,189, 190,192, 205,206, 208,221, 224

Stüßer N. 6, 39, 40, 43,45, 46, 48,50, 52, 53,

57, 58, 67, 74Süllow S. 41Suzuki K. 194Svoboda P. 11, 18, 51Swerts J. 88, 89, 90Szymczak H. 65Szytula A. 45, 46, 52,

53, 54, 55

TTatchev D. 193te Velthuis S. 218, 219Temst K. 88, 89, 90Tennant D.A. 81, 82Terada N. 31Toader A. 4Többens D.M. 12, 64, 66,

74, 103, 172,174, 189,207, 217

Toda M. 72Tomuta D.G. 61, 62, 63Torok G. 150Tovar M. 64, 65, 102,

104, 105, 191Tran V.H. 40Treimer W. 60, 226, 227,

228, 229,230, 231

Triolo A. 106, 121,122, 123,

126, 132, 139Triolo R. 121, 122,

123, 132Trombach U. 182Troyanov S. 100

UUlbricht A. 208Ulrich C. 36, 37, 38, 79

VVan der Zwaag S. 195van Dijk N.H. 195van Hasendonck C. 89Vasi C. 120Vasiliev A.D. 97Vassen R. 205Vejpravova J. 11, 18Vogl G. 106von Klitzing R. 145Vorderwisch P. 75, 80, 110Vrchovinsky V. 192

WWagh A.G. 226Weitzel H. 58Welker C. 105Wesemann A. 146Wiedenmann A. 164, 167,

181, 187,190, 197,198, 199,200, 201,202, 203,204, 214,221, 222,223, 224

Willumeit R. 153, 154Wilmer D. 113Wilpert Th. 222, 223Winterer M. 203, 204Witte U. 10Wolff M.W. 59, 129Wozniak K. 98

ZZabakhsh A. 151Zabel H. 129Zapf A. 135Zeitelhack K. 221, 224Zrník J. 192

hmi - b 584

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