####################################################
# Seunghun Lee <shl@nist.gov>
# requesting 3 days, at minimum=2 days
# beamline 33BM, Structural studies on a geometrically frustrated magnet ZnV2O4
# instrument 33BM-C fourc
####################################################
# top:/home/www/beamtime-requests/req00550.txt
# UNICAT Member Beam Time Request  #550
# created Thu Jan 22 09:39:42 CST 2004
####################################################

beamline:
	33BM

collaboration:
	No

collaborator_Paul:
	ON

contact:
	shl@nist.gov

days:
	3

description:
	ZnV2O4 is an excellent system to study the intricate interplay between spin, orbital and lattice degrees of freedom in geometrically frustrated magnets because the magnetic V3+ (3d^2) ions have orbital degeneracy. Upon cooling, this system undergoes a cubic-to-tetragonal phase transition at 50K and a magnetic long-range order at 40K. Recently we have reported by inelastic neutron scattering that magnetic correlations become one-dimensional in the tetragonal phase while they are three-dimensional in the cubic phase[1]. We proposed a model of antiferro-orbital ordering of the t_2g orbitals of the vanadium ions to explain the cubic-to-tetragonal distortion and the dimensional transition of the magnetic interactions. The antiferro-orbital ordered state has I41/a symmetry. There are other possible orbital ordering patterns, such as a ferro-orbital ordered state which has I41/amd symmetry. Finding out which orbitally ordered state is correct is crucial in understanding the nature of the phase transition and it requires single crystal X-ray measurements. We would like to search for several possible reflections that are allowed for one symmetry but not for the other.

These measurements would require 3 days of the 33BM beamline.

[1] S.-H. Lee et al., cond-mat/0312558.

equipment_required:
	Displex

experiment:
	Structural studies on a geometrically frustrated magnet ZnV2O4

foreign_nationals:
	Hiraoki Ueda, University of Tokyo, JAPAN

hazards:
	NONE

instrument:
	33BM-C fourc

instrument_other:
	

minimumdays:
	2

name:
	Seunghun Lee

new_request:
	ON

nonmembers:
	

unacceptable_dates:
	NONE

z34ID_change_undulator:
	no

z34ID_details:
	

z34ID_parasitic:
	yes


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