seminor ansto-0730

My approach to magnetism

- with Pair Distribution Function (PDF) analysis,

magnetic structural analysis,

and inelastic neutron scattering techniques

NSRRC, instrument scientist SIKA@ANSTO

Dr. Shinichiro Yano

Prof. Jun Akimitsu

“But please remember: This is only a work of fiction.

The truth, as always, will be far stranger.”

Arthur C. Clarke

“You can’t be a physicist by choosing to be a theorist. But you are

good at calculations, so I give you the subject which requires neutron

scattering. You need to be strong in both theory and experiment.”

Jun Akimitsu

Sheldon: Penny, I am a physicist. I have a working knowledge

of the entire Universe and everything it contains!

Penny : Who is Radiohead?

Sheldon : I have a working knowledge of the important things

in the Universe. (Big bang theory, season 2 )

How I became a experimental physicist.

Year Job Place Neutron

source

Material Experiences

2005-

2006

Undergrad

uate

Aoyama

-Gakuin

(Tokyo),

JRR3M CuB2O4 Thermal TAS

(Diffraction)

2006-

2008

Master Aoyama

-Gakuin

(Tokyo),

JRR3M, (Sr,Y)CoO3

MnP

Hard X-ray,

Thermal TAS

2008-

2012

Ph.D Aoyama

-Gakuin

(Tokyo)

JRR3M, J-

PARC

MnP

Ba2Mg2Fe12O

22

Earth quake,

Thermal TAS, Cold

TAS, Four circle,

Chopper

2012-

2014

Postdoc Univ. of

Virginia

NIST-NCNR,

SNS- ORNL,

HFIR-ORNL

LuMnO3,

NiS2-xSex

(La,Y)VO3

Chopper (SNS),

PDF machines,

Cold Chopper

(NIST)

2014

Nov.

- present

Instrument

scientist

NSRRC,

ANSTO

Bragg

institute

NiS2, MnP,

CoO, LuMnO3

Cold neutron TAS

SIKA

Year Job Place Neutron

source

Boss

2005-

2006

Undergrad

uate

Aoyama

-Gakuin

(Tokyo),

JRR3M

2006-

2008

Master Aoyama

-Gakuin

(Tokyo),

JRR3M,

2008-

2012

Ph.D Aoyama

-Gakuin

(Tokyo)

JRR3M, J-

PARC

2012-

2014

Postdoc Univ. of

Virginia

NIST-NCNR,

SNS- ORNL,

HFIR-ORNL

2014

Nov.

-present

Instrument

scientist

NSRRC,

ANSTO

Bragg

institute

Prof. Shinichi Itoh(KEK)

Prof. Louca Despina

(Univ. of Virginia)

Dr. J.S. Gardner (NSRRC)

Prof. Jun Akimitsu (Aoyama-Gakuin)

What is the structures?

◦ Crystal structure, Local structure, Magnetic structure

How do they behave?

◦ Diffuse scattering, spin wave, phonon, dynamic local

structure, crystal field excitation

Why is the magnetism?

The Study of Magnetism

What?

How?

Why?



How do they behave?


structure, inelastic scattering


Magnetism – with PDF analysis

“He(Floyd) had already decided that X rays, sonic probes, neutron beams , and all other

nondestructive means of investigation would be brought into play before he called up the

heavy artillery of the laser. Clarke, Arthur C. 2001: A Space Odyssey

Bragg diffraction

(long range order)

Total scattering data

Reciprocal space

Fourier Transform

Pair density function (PDF) is obtained via Fourier transform of the normalized

elastic total scattering structural factor S(Q) (static PDF)

Rietveld refinement

Long-range periodic

structure (average structure)

Real-space refinement

Short-range structure

(local structure)

PDF

Rietveld vs PDF

Comprehensive understanding about structure

Ni-OO-O

Kinds of PDFs

Ready for 3 beams,

◦ Neutron = most common but very competitive

◦ X-ray = hottest now but resonances from Q = 30 Å-1

◦ Electron = most promising but needed to be commissioned

Ready for 3 methods with neutron scattering

◦ Static PDF

“Underneath the Bragg Peaks” by T.Egami and S.J.L.Billinge

◦ Dynamical PDF

Theory: T.Egami et al. (2012)

Experiment: Dmowski,(2008), Bing Li et al. (2014),

◦ Magnetic PDF

Experiment : Wu et al. (1987) B.A. Frandsen (2015)

Thoery and modeling : B.A. Frandsen (2014)(1st 2003, 2nd 2012)

Static PDF procedure

NOMAD@SNS

Bragg peaks are for Rietveld Analysis

PDFgetN: http://pdfgetn.sourceforge.net/

1 2 3 4

-2

0

2

4

6

G (

r)

r (A)

2K

30K

70K

100K

150K

200K

250K

300K

Average structure

(crystal structure)

Local structure

If Average structure explained

the pattern well, it means there

would be no local structure.

If Average structure did not explain

the pattern well, find out the local structure

x > 0.20, long range orbital order state disappear. Below TN,

G-SO phase in Y-rich region and C-SO phase in La-rich region

J.-Q Yan et al., Phys. Rev. B 84, 214405 (2011).

LaVO3

T = 143KG-type OO

C-type SO

YVO3

(T < TSO2)

C-type OO

G-type SO

LaVO3

G-type OO

C-type SO

The phase diagram of (Y,La)VO3

P21/a

P21/a

Pnma

Pnma

Pnma

Pnma

2.0 2.5 3.0 3.5 4.0 4.5 5.0-0.1

0.0

0.1

0.2

0.3

0.4

2.0 2.5 3.0 3.5 4.0 4.5 5.0

0.0

0.1

0.2

0.3

0.4

3.9 4.0 4.1 4.2 4.3 4.4 4.50.04

0.06

0.08

0.10

0.12

0.04

0.08

0.12

3.8 4.0 4.2 4.4

0.04

0.08

0.12

(e)

(d)(c)

r (Å)

r (Å)

PD

F (

Å-3

)

5 K 50 K

150 K 300 K

(a)

PD

F (

Å-3

)

Data at 150 K

P21/a model

Difference

(a)

Data at 250 K

Pnma model

Data at 250 K

P21/a model

Local structure YVO3The local G orbital pattern in P21/a

Y-O

V-O

0 50 100 150 200 250 300

3.99

4.02

4.05

4.08

4.11

2.0 2.5 3.0 3.5 4.0 4.5 5.0

0.0

0.1

0.2

0.3

0.4

0.5

5K Pnma model

300K Pnma model

(b)

(a)

O-O short

O-O long

Y0.7

La0.3

VO3

PD

F (

Å-3

)

-0.2

-0.1

0.0

0.1

0.2

0.3

O-O

pai

rs (

Å)

r(A)

Temperature (K)

TN

The new phase of local orbital ordering

The local C-OO was observed in

this system.

S.Yano et al., Phys. Rev. B 90, 214111 (2014).



How do they behave?

◦ Diffuse scattering, spin wave, phonon,

dynamic local structure inelastic scattering


Magnetism – with magnetic structure

“I think a good framework of thinking is physics. You know sort of the first principal of

reasoning. Boil things down to the fundamental truth, and reason up from there

When you wanna do something new, you have to apply physics approach. Physics is

the sort of figuring out how to find new things counterintuitive.”

Elon Musk.

Picture from TED

(2013)

Crystal structure symmetry (Space group)

Magnetic atoms

You have model??

2

2

, 2exp)()(69.2 3

i

ii

mag

Fehklhklmag rQQsQQfFI

Find the default values

Generate random values

for magnetic sites which

show low χ2

Magnetic point group theory Model Free

You need constraints?

i

calc

i

obs

i lkhFlkhF 22 )),,(),,((

The parameters are the number of magnetic atoms*3(x,y,z)

Neutron scattering intensities

Least square method

You got an answer!! Check your answers

1. Agree with physical picture

2. Add F=0 points as data, check χ2

3. Explain other experiment results?But, are you sure ??

S = Spins

q = The projection

of Spins

QsQ i

The phase diagram of NiS2-xSex

NiS2 cubic Pa-3 (No. 205)

Ni fcc structure at 4a (0, 0, 0)

P.G. Nikolowitz et al. Phys. Rev. B. 77 (2008) 115135

T. Miyadai et al. JMMM 31-34

(1983) 337-338

M2 disappear at around x = 0.3

M1 disappear between x = 0.6 and 0.8.

AFM M1 k = (0 0 0); 1st order

AFM M2 k = (1/2 1/2 1/2) 2nd order

NiS2-xSexAFM M1

1.0 1.5 2.0 2.5 3.0 3.5 4.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0.8 1.0 1.2 1.4 1.6 1.8

0.4

0.6

0.8

1.0

1.2

T = 2 K

Inte

nsi

ty (

arb.

un

its)

N(222)

N(311)

N(220)

N(211)

N(210)

N(200)

N(111)

M1+M2 phase

M2 phase

M1 phase

M2(1/2 1/2 3/2)

M1(110)M1(100)

M2(1/2 1/2 1/2)

Q (Å-1)

The powder neutron diffraction NiS2

The magnetic structure for M1 Ni fcc with k = (0 0 0), M1: Г1 𝟁1(Ni = 1.0 mB at NiS2

Ma Mb Mc

0.577 0.577 0.577

0.577 -0.577 -0.577

-0.577 0.577 -0.577

-0.577 -0.577 0.577

To be compatible with M1, mM1i mM2i= 0

Candidate for magnetic structure M2

Ni fcc with k = (0 0 0) k = (1/2 1/2 1/2)

Ma Mb Mc

0.577 0.577 0.577

0.577 -0.577 -0.577

-0.577 0.577 -0.577

-0.577 -0.577 0.577

M1: Г1 𝟁1(Ni = 1.0 mB at NiS2

M1 and M2 are normal to each other mM1i mM2j= 0

Candidate for magnetic structure M2

M1 M2

Г1 𝟁1 Г1 𝟁1

Г1 𝟁2

Г1 𝟁3

Г1 𝟁4

Г3 𝟁5

Г3 𝟁6

Г3 𝟁7

Г3 𝟁8

Ex.) Г1 𝟁1(M1) Г1 𝟁2(M2)

Ma Mb Mc

6 6 6

6 -6 -6

-6 6 -6

-6 -6 6

Ma Mb Mc

4.732 -4.732 0

2.732 -2.732 5.464

0.732 2.732 2

-2.732 0.732 -2

= 0

Г1 𝟁2, Г1 𝟁4, Г3 𝟁6, or Г3 𝟁8 are possible.

The magnetic structure in NiS2

Г1 𝟁2, Г1 𝟁4

Г3 𝟁6, Г3 𝟁8,

The four magnetic domains in NiS2

S.Yano et al. PRB submitted (2015)



How do they behave?

◦ Spin wave, Diffuse scattering, phonon,

dynamic local structure, inelastic scattering


Magnetism – with inelastic neutron

“On principal, it is quite wrong to try founding theory on observable magnitude alone

In reality the very opposite happens. It is the theory which decides what we can observe.”

Albert Einstein.

The anomalous dispersion in MnP

Eq=70q2+0.4(meV)

Eq=145q2+0.4(meV)

Eq=86q3+0.4(meV)

We need to determine the dispersion relation of MnP in the

whole Brillouin zone

Y.Todate et al,J.Phys.Soc.Jpn., 56, 36 (1987)

Ferromagnetism phase

∝ q3 indicate unusual

energy excitation.

Inelastic Neutron Scattering@JRR3M

Single Crystal: 9mmΦ× 50 [mm3]

1. LTAS（Low Energy)

With high resolution

Ef fix : 3.0meV, T = 53K, LT

Collimation 10’ -80’-80’- open

2.TOPAN（Middle Range Energy)

Ei fix : 13.5meV, T = 53K,LT

Collimation 60’-60’-60’-60’

3.TAS-1（High Energy）

Ef fix : 14.7meV, T = 60K

Collimation B-80’-80’-B

2. TOPAN

1. LTAS

3. TAS-1

0.0

15

30

45

60

0 0.2 0.4 0.6 0.8 1

LTAS

TOPAN

TAS-1

E (

meV

)

(h,0,0)

Magnetic Excitations in MnP@TAS’s

High energy and

High resolution

0.0

2.0

4.0

6.0

8.0

0 0.1 0.2 0.3 0.4

LTASTOPANTAS-1

E (

meV

)

(h,0,0)

1. 2 branches ?

2. Clear discrepancy from q3 model

Eq=86q3+0.4(meV)

The character of HRC：HRC delivers high-resolution and

relatively high-energy neutrons for

a wide range of studies on the dynamics of materials.

Vacuum Camber

High Resolution Chopper Spectrometer

The detectors cover -10 to 40°(The design was -31 to 124°)

PSD detector

DAQ-middleware system for HRC

DAQ electronics

33 of Neunet

Storage

Device

CPU+Labview program (by Satoh)DAQ-middleware

On-Off

PSD

Event data are stored in

/home/daq/hrc/

256 of Position

Sensitive Detector

Schematic configuration neutron path

qa = ki cosy − kf cos (fH − y) cosfV,

qb= ki siny + kf sin (fH − y) cosfV ,

qc = ki sinfV,

Scan trajectories on a chopper spectrometer in energy-momentum space.

Measurements of excitations in a one-dimensional system and a three-

dimensional system.

Neutron Inelastic Scattering

Analysis of 4 Dimensional E-Q Spacea*-b*（Qc=0：-~+） b*-E

a*-c*（Qb=2：2-~2+） c*-E

3

2

1

Qb

(rl

u)

-1 0 1Qa (rlu)

(a)

3

2

1

Qb

(rl

u)

3020100E (meV)

(b)

-1

0

1

Qc (

rlu

)3020100

E (meV)

(d)

-1

0

1

Qc (

rlu

)

-1 0 1Qa (rlu)

(c)

MnP

Figure: Dispersion relation of the spin waves in the ferromagnetic phase of MnP

along the a* and b*-axis. We assumed isotropic 6th exchange parameters and

calculated dispersion relation using the Heisenberg model for 2-sub lattices.

Spin waves in MnP

J1 = 0.377 ±0.14, J2 = 0.657 ±0.10, J4 = 0.067 ±0.13,

J5 = 0.267±0.10, and J6 =0.647 ±0.08 meV

Takeuchi and Motizuki discussed a mechanism of the transition

from the ferromagnetic phase to the proper screw spiral phase,

Helimagnetism and Exchange Interaction

J4 0

,

The obtained exchange constants in the ferromagnetic phase of MnP as listed in

Table 2 satisfy the conditions in eqs (1), (2), (3) and the condition in eq. (4) is

not satisfied.

J2/J

41

J6 cos

9

J

4

2 0

J1 2J

5 2cos

9

J4

…(1)

…(2)

…(3)

…(4)

S.Takeuchi and K.Motizuki J.Phys.Soc.Jpn 27 No.4 742 (1967)

J1 = 0.377 ±0.14, J2 = 0.657 ±0.10, J4 = 0.067 ±0.13,

J5 = 0.267±0.10, and J6 =0.647 ±0.08 meV

: Mn

: O

: R

ab

c

Hexagonal RMnO3

(Y, Lu, Ho, Yb)

Space group P63cm

High TC ~ 1000 K

TN ~100 K (LuMnO3 = 86 K)

Mn3+ forms triangular lattice

N.N. = 3.48Å

z=0

z=0.5G4 representation

Crystal structure of RMnO3

A. Munoz et al. PRB 62 9498(2000)

P. Tong et al. PRB 86 094419(2012)

S. Lee et al. Nature 451 805(2008)

DCS@NCNR(U.S.A)

=4.5 Å. dE = 0.142meV

Q range 0.12 - 2.6 Å-1

with 40g of powder sample

Q(Å-1)(a) At 4 K under TN, it is barely present.

(b) At 100 K just above TN,the scattering is intensified

(c) At 180 K above TN, it subsides, but still exists up to 250 K.

70 75 80 85 90 950

50

100

150

Inte

gra

ted

inte

nsity a

t (1

01)

Temperature (K)

2b0.403TN 87.9K

The magnetic scattering at (101)

The magnetic intensity at (101) follows a

power law dependence,

which is typical of 2D AFM systems

𝐼 ∝𝑇

𝑇𝑁− 1

2𝛽

𝑤𝑖𝑡ℎ 𝛽 = 0.20Q ~ 1.20, 2.40 Å-1 are correspond

to Mn-Mn N.N. and N.N.N.,

Lorentzian functionAsymmetric

Symmetric

T ~TN

T >>TN

Warren 2D

Connection between FE and 2D

TN, where all glide and mirror planes are eliminated

P. Tong et al. PRB 86 094419(2012)

Mn-O3-Mn ≠ 120 degree.

Release magnetic frustration

Local structure

P63cm -> P63



How do they behave?


structure


Magnetism@ ANSTO, NSRRC

“Tactics is knowing what to do when there is something to do; strategy is knowing what

to do when there is nothing to do. Why? Turns Tacticians into Strategists”

Garry Kasparov

Cold Triple axis in the world

LTAS, C11

(stopped, JRR3M)

CTAS

(under commission, HANARO)

SIKA

(will start user commission)

CHINA

(construction, CARR)

PANDA

(Germany FRM-II)IN14

(Frence ILL)

SIKA will be very important

1. Only one Cold TAS starts user program in Asia-Oceania area soon

2. Neutron flux at sample position is (will be) good

MACS, SPINS

(NIST,NCNR)CTAX

(HIFR,ORNL)

Why we need Cold TAS Interactive (with chopper at spallation source)

The magnetic scattering (magnetic form factor)

The environment (with H, P, T, and polarized neutrons)

0.1 1 10

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Momentum Space Q (Å-1

)

Mn

Man

get

ic F

orm

fac

tor

F(Q

)2

0.01

0.1

1

10

100

1000

En

ergy

(meV

)

Chopper

Thermal TAS

Cold TAS

To the future

“Intelligence should be viewed as a physical process that tries to maximize future freedom

action and avoids the constraints its own future.”

Alex Wissner Gross.

𝐹 = 𝑇 𝛻 𝑆𝜏

𝑃𝑡ℎ𝑖𝑠 𝑐𝑦𝑐𝑙𝑒 = 𝑅𝑚𝑒 + 𝑅𝑢𝑠𝑒𝑟𝑠(𝑆𝑢, 𝑆𝑠, ) 𝛻𝑅𝐴𝑂𝐶𝑛𝑒𝑥𝑡 𝑐𝑦𝑐𝑙𝑒

Intelligence is a force F that acts with

T = reservoir temperature (strength)

S = the entropy associate with microstate

(𝛻 𝑆 = Diversity of possible accessible futures)

𝜏 = up to future time horizon PRL 110 168702 (2013)

Picture from TED

The magnetic structure of NiS2 in single crystal

◦ Wombat, Koala (2015, Jan.)

◦ SIKA (2015, Jun.)

The superconductivity on MnP

◦ D20, D23 in ILL, France (2015, Dec.)

◦ SIKA (2015, Aug)

◦ J-PARC, Japan (2016?)

The multiferroic of (Lu,Y)MnO3

◦ Pelican (2015, Nov.)

◦ NOMAD ORNL, U.S.A (2015, Sep.)

Magnetism

“Science is made by men, a self-evident fact that is far too often forgotten”

Werner Heisenberg