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
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