College Park, Maryland      June 6 - 10 , 2004

W2-D3 (2:15 PM): Spin, orbital, and lattice couplings in a geometrically frustrated magnet CdV2O4

Z. Zhang, A. Visinoiu, D. Louca (Department of Physics, University of Virginia), Y. Qiu, S. Park (NIST Center for Neutron Research), T. Proffen, J. Thompson (Los Alamos National Laboratory), S.-H. Lee (NIST Center for Neutron Research)

The microscopic properties of the vanadate spinels are distinctly different from those of the chromates due to the intrinsic orbital degeneracy of the vanadium ion. We studied a vanadate compound, CdV2O4, to investigate how the orbital degree of freedom couples to the lattice and spin. CdV2O4 undergoes a cubic-to-tetragonal transition at 87 K and a magnetic long range order at 35 K. This contrasts with the chromates where a tetragonal distortion and a magnetic long range order occurs simultaneously due to a spin-lattice coupling. We have performed neutron diffraction and inelastic neutron scattering measurements on a powder sample of CdV2O4. Upon cooling, the Q-lineshape of the inelastic scattering intensity changes from symmetric in the cubic phase to asymmetric in the tetragonal phase. This indicates that the vanadate becomes a system of weakly coupled straight chains in the tetragonal phase. We will discuss implication of the results to the interplay between the orbital, spin and lattice degrees of freedom in the vanadates.

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