spin polarized inelastic neutron scattering nist summer school on neutron spectroscopy seung-hun lee...

Spin Polarized Inelastic Neutron Scattering

NIST Summer School on Neutron Spectroscopy

Seung-Hun LeePeter GehringSungil Park

Alina VisinoiuGokhan CaliskanErick LawsonMartin SulicTessema Guebre XabiherKapil GuptaJose RodriguezMike Lewis

O

AB

Edge-sharing octahedra

CW = -390 KTN = 12.5 KCorner-sharing tetrahedra (B sites)

Magnetic Phase Transition in ZnCr2O4

AFM

AFM

AFM

H = -J Si . Sj

All exchange interactions can not be satisfied.

Magnetic frustration

or

ZnCr2O4-Space Group-Fm3d

SPINS

Monochromator

Sample

Analyzer

Single DetectorNeutron Source

Sample

Flat Analyzer

Position-SensitiveDetector

2i

aa

i

Increased data acquisitionRate over conventional TASBy an order of magnitude.

Exploring Statics

Q(Å-1)

Inte

nsit

y

•Q resolution~0.02 Å-1

•Doubling of the unit cell

(H,K,L)=(1,1,1)

(1/2

,1/2

,1)

(1/2,1/2,3/2)

Order Parameter

Exploring DynamicsEnergy scans at fixed Q at 2K and 15K

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

-1 0 1 2 3 4 5 6 7

Energy [meV]

I [c

ts]

2K

15KQuasielastic

Inelastic

Inelastic Resonance Peak

-Correlation LengthT=15K>TN

0.6meV<E<1.4meVHWHM=~0.45Å~2.2Å

T=1.5K<TN

4.2meV<E<1.4meVHWHM=~0.36Å~2.8Å

Summary• SPINS probes both the static crystal and

magnetic state of the system.• SPINS probes the dynamic behavior of the

system.• SPINS is a relatively fast spectroscopy

technique. • SPINS is ideal for studying specific regions

in Q- space.

Acknowledgements:•NIST•NSF•NCNR