Karine CHESNELALS

WORKSHOPMagnetic Nanostructures,

Interfaces, and New Materials: Theory, Experiment, and Applications

Collaborations

“Flangosaurus”

Zahid Hussain, ALS Support Tom Miller, Soren Prestemon, John Spring, John Pepper, …

Steve Kevan University of OregonJoshua Turner

Jeffrey Kortright Lawrence Berkeley Lab

Eric Fullerton Hitachi, San Jose

Olav Hellwig (BESSY, Germany)

Larry Sorensen University of WashingtonMichael Pierce

Shouheng SUN IBM, New York

Kannan KRISHNAN University of Washington

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OutlineOutline

IntroductionIntroduction

The coherent scattering endstation at ALSThe coherent scattering endstation at ALS

First investigations on nanoparticlesFirst investigations on nanoparticles

Different way to use magnetic Speckle Different way to use magnetic Speckle

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How obtaining magnetic speckles?

Magnetic Structure

(nanoscale)

Coherentillumination

Pinhole

Spatial filtering:

Transversecoherence

Light(Soft X)

TemporalCoherence

Detector

ResonantScattering

Magnetic Speckle pattern

Short range magnetic orderLocal disorder

J. Kortright K.Chesnel

Coherent Soft X-Ray Beamline (BL12.0.2)

Optimization of the beam

= 2.48 nm (500 eV)d = 2.5 µm

Rosfjord et al. (2004)

Energy range 200-1000eV

Coherent flux at 500eV:~ 5 1010 ph/sec/0.1%BW

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Scatteringin

Transmission

X rays

Samplelocation

Coherent Soft X-ray Magnetic Scattering endstation

Flangosaurus

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Scatteringin

Transmission

ScatteringIn Reflection

X rays

Samplelocation

Flangosaurus

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Flangosaurus

Octopolar magnetUnit pole

H

x

y

z

Produce Magnetic field in any directionMaximal amplitude 0.6 T

WaterCoolingsystem

CurrentInput

(100A)

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Flangosaurus

Scatteringchamber

Light

Opticaltable

CryogenicSample-holder

Magnetic manipulator

Load-lockchamber

Bellow

Samplelocation

Rotationbrackets

Pressure10-8 mBar

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Flangosaurus:Cryogenic Sample holder + pinhole mechanism

feedback

InchwormBender

Sampleholder

3 pinholesholder

HorinzontalMotion

(13 mm)

VerticalMotion

(1.5 mm)

5 mm

Pinhole size: few mGood oversampling

Near field

Mechanicalisolation

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• Control of pinhole positioning

• High oversampling condition

• In-situ 3D magnetic field

• Sample cooling (cryostat)

• Investigation of the full main scattering

plane

• 2D detection with high resolution

• Fast detection

Experimental possibilitiesExperimental possibilities

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Different geometries specificitiesDifferent geometries specificities

• Any kind of substrate

• Possibility to vary the incidence angle (f’,f’’)

• Depth sensitivity

• Discrimination of themagnetic components

ReflectionReflection• Use of membrane

• Simple measure of transmitted light (f’’)

• Direct image in the reciprocal space

• Transmitted beam easy to block

TransmissionTransmission

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Probing the magnetism in nanoparticlesProbing the magnetism in nanoparticles

-6 10-7

-4 10-7

-2 10-7

0

2 10-7

4 10-7

6 10-7

8 10-7

0 50 100 150 200 250 300 350

P11A10 ZFC/FC

Temperature

Super-paramagnetic

Blocked

Blocking temperature

Resonant soft X-ray scattering

- Probe the magnetic order/disorder- effect of field and temperature- slow and fast dynamic

Co nanoparticles Self-assembly

Mesoscopic Scale

~10nm particles

Magnetic configuration

of the nanoparticles ?

?

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Probing the magnetism in nanoparticlesProbing the magnetism in nanoparticles

Different systems under study:

Co particles 8-9nm (variable packing)Co particles 8-9nm (variable packing)

FeFe33OO44 particles variable size 4-16nm particles variable size 4-16nm

Sources S. Sun, K Krishnan…

Kortright et al. (2004)

I0

Magnetic fieldScattered light

(SAXS)

Transmitted light (XMCD)

Transmission geometryIncoherent light XMCD, SAXS

(average information)

Coherent light speckle pattern (average information)

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Characterization with polarized light (BL4)Characterization with polarized light (BL4)

750 760 770 780 790 800

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03750 760 770 780 790 800

200

400

600

800

1000

1200

1400

1600

XMCD

Energy (eV)

Co nanocrystals: Sample 2

Transmitted intensity plus minus L3 L2

XMCD

0.1 0.2 0.3 0.4 0.5 0.6

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

F

Normalized intensity

q (nm-1)

Co Nanoparticles

AF

Incoherent scattering

Co L3 edgeInterparticle

distance~12nm

Correlation length~60nm

-10 -5 0 5 100.095

0.100

0.105

0.110

0.115

0.120

0.125

0.130

0.135

Intensity

Field (kG)

P+ P-

AF peak

beam current normalization

25% XMCD

-10 -5 0 5 1024

26

28

30

32

34

36

38

Intensity

Field (kG)

P+ P-

FERRO peak

beam current normalization

35% XMCD

I0

Magnetic fieldScattered light

(SAXS)

Transmitted light (XMCD)

Co nanocrystals

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Coherent 2D scattering on nanoparticles

Co Nanoparticles assemblyprecipitated on TEM grid

X –ray beamtuned to resonant edge

Diffuse scattering

Pinhole(coherence)

CCDCamera2048x2048

Energy optimized at Co L3 edge: =1.58 nm

750 760 770 780 790 800 810 820 8300

2

4

6

8

10

12

14

16

18

20

Intensity (normalized)

energy (eV)

integration of diffuse peak normalized by M5

L3

L2

Co nanoparticles (A9)

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TEM image (K.Krishnan)

VERY HERTEROGENEOUS!!

Localized peaks => Ordered

area

IsotropicPattern

Another Ordered area

General 2D scattering Patterns (no pinhole)

ALL patterns distributed along a RING

• ordered area d~ 12nm• disordered d~ 13nm

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Effect of magnetic field in linear polarization

X rays

Hperp

Hpar

Scattering peak (charge +magnetic)

Fullscattering

DifferenceRemanence-Saturation

With PERPENDICULAR field: I (saturation) > I (remanence)

(Effect ~0.5%)

With IN PLANE field: I (saturation) < I (remanence)

At saturation all particle moment are pointing the same direction and contribute to the peak

With linear polarisationX rays are not sensitive to the in plane component

- Ordered area

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Effect of magnetic field – isotropic area

X rays

Hperp

Hpar

With PERPENDICULAR field: I (saturation) > I (remanence)

Effect ~4%

DifferenceRemanence - Saturation

Full scattering

Scattering signal(charge +magnetic)

It seems isotropic areas show a strongertendency to AF order at remanence, while ordered area are more F…

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Obtaining a Speckle pattern:Obtaining a Speckle pattern: degree of coherence/ pinhole size (Co edge) degree of coherence/ pinhole size (Co edge)

200 400 600 800 1000 1200 1400 1600 1800 2000

200

400

600

800

1000

1200

1400

1600

1800

2000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

x 104

200 400 600 800 1000 1200 1400 1600 1800 2000

200

400

600

800

1000

1200

1400

1600

1800

20000

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

No pinhole 10sec

5 m pinhole 100s 3 m pinhole 300s

C=1%

200 400 600 800 1000 1200 1400 1600 1800 2000

200

400

600

800

1000

1200

1400

1600

1800

2000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

x 104

25 m pinhole 100s

C=3%

C=12%

200 400 600 800 1000 1200 1400 1600 1800 2000

200

400

600

800

1000

1200

1400

1600

1800

20000

200

400

600

800

1000

1200

1400

1600

1800

2000

C=25%

NC

1∝

…Dainty law

Transverse coherence

lengthc~1m

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Static spatial cross correlation (metrology)Static spatial cross correlation (metrology)Slow dynamic on spatial correlationSlow dynamic on spatial correlationFast dynamic time correlationFast dynamic time correlation

What the Speckle pattern tell us?What the Speckle pattern tell us?

Speckle pattern Autocorrelation pattern

Specklesize

Background(incoherentScattering)

Three Ways to use the speckle

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1. Static Speckle metrology1. Static Speckle metrology

Cross-correlationbetween two

speckles patternsA and B

A

B

( ) [ ][ ] [ ]∑ ∑∑

⊗⊗

⊗>=<

BBAA

BABA,ρ

Correlation coefficient

Magnetic Memory

Pierce et al. PRL 90, 175502 (2003)

= 0 no memory= 1 total memory(exact same pattern)

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Major Loop Return and Conjugate Point Memory

major loopA

B

C

A Starting pointB Conjugate PointC Return Point

A x B = CPMA x C = RPM

1 2 3 4 50.75

0.80

0.85

0.90

0.95

1.00

RPM

CPM

RPM

Rho

image number

perpendicular field in-plane field

perpendicular field in-plane field

CPM

Cross correlation

Ordered area

Disordered area

VERY HIGH MEMORY ! K.Chesnel

2. Slow dynamic2. Slow dynamic

Diffuse ring(disordered area)

Each frame: 10 sec

Diffuse ring(disordered area)Each frame: 3 sec

Evolution of the slow dynamic versus temperature

• Speckle correlationdecreases with time• Decay slope depends on temperature

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Price, Sorensen, Kevan et al. PRL 82, 755 (1999)

Time autocorrelation

∫ −= dttItIg )().()( ττ

MCP

HV

PositionAnalyzer

DigitalCorrelator

Pre-amp

X

Y

Z

Oscilloscope in XY mode

Detector

Scattering signal

Time scale:sec1sec1 <<τ

ScatteringSignal

I (t)

Principle

3. Fast dynamic3. Fast dynamic

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Fast dynamic measurements: First results on Fe3O4 nanoparticles

1E-3 0.01 0.1 1 10 100 10000

1

2

3

4

5

6

7

8

9

10

Accessible range forsample fluctuations

Synchrotron

noise

Time Autocorrelations on Nanoparticles

Autocorrelation

Lag time (ms)

Afterpulsingeffect

0.1 1 10

1.00

1.01

1.02

1.03

1.04 Measurment Exp decay fit

Autocorrelation

Lag time (ms)

τ=1.7ms

Fe L3 edge25 m pinhole/sample300 m hole/detector

Intensity 15 000 cps/sec

• Evolution with T (through blocking transition)• Effect of magnetic field

Map the dynamic (H,T)K.Chesnel

ConclusionConclusion

New endstation for coherent magnetic scattering New endstation for coherent magnetic scattering now functional at ALS BL12now functional at ALS BL12

First investigations on Co and Fe3O4 nanoparticles First investigations on Co and Fe3O4 nanoparticles with coupled measurements in with coupled measurements in incoherentincoherent light (XMCD, light (XMCD, SAXS) and SAXS) and coherentcoherent light (speckle) light (speckle)

Static speckle study: magnetic memoryStatic speckle study: magnetic memory

Slow dynamic: time scale > 1sec Slow dynamic: time scale > 1sec

Fast dynamic: time scale 10 Fast dynamic: time scale 10 sec – 1secsec – 1sec

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“Speckle” techniques

• Speckle Metrology (spatial)

• Slow and fast dynamic

• Lensless magnetic imaging

Candidates

•Metallic thin filmsCo/Pt, FePd, FePt…

• Patterned media

• Nanoparticles

• Exchange bias

• Manganites CMR

• Cuprates superconductivity

Physics

• Local magnetic configuration

• Magnetic memory

• Spatiotemporal fluctuations

• (Temperature, field) transitionsK.Chesnel