Geometric frustration in CuV2S4

A cubic spinel conductor CuV₂S₄, containing the corner-sharing tetrahedral lattice of V, was investigated. Above a structural transition at 90 K, the ⁵¹V nuclear spin-relaxation rate 1/T₁ is comparatively large in magnitude and tends to saturate at higher temperatures, indicating that the V lattice behaves as a nearly antiferromagnetic metal. By substituting nonmagnetic Sn for V, the susceptibility turns to be of Curie-Weiss type and temperature-independent, suggesting recovery of hidden spins as a result of a partial release of the frustration. These results lead to the conclusion that CuV₂S₄ is an itinerant-electron frustrated system as YMn₂. The CDW transition of CuV₂S₄ accompanied by a tetragonal distortion which may be understood as a result of lowering of interaction dimensionality inherent to the corner-sharing tetrahedral lattice.