Cation partitioning in ternary vanadium sulfides2S4 (A=Ti, Cr, Fe, Ni)

Abstract

A combination of time-of-flight powder neutron diffraction and powder X-ray diffraction has been used to investigate changes in the cation distribution in a series of isostructural (space group I2/m a≈5.9, b≈3.3 c≈11.3Å, β≈92°) ternary vanadium sulfides, AV ₂ S ₄ (A=Ti, Cr, Fe, Ni). A progressive change from an inverse Cr ₃ S ₄ structure, when A is drawn from the left of the transition series, to a normal Cr ₃ S ₄ structure, when A is drawn from the right of the series, occurs. The magnetic susceptibility of all materials has a significant temperature-independent component and both spin-glass behaviour [A=Cr, T _g =15(3) K] and long-range magnetic order [A=Fe, T _N =135(3) K] are observed.