Study of the spin-glass transition in FeCr2xIn2-2xS4 thiospinel

The spin-glass (SG) transition in Fe(In2-2xCr2x)S4 thiospinel with x=0.1 and 0.3 has been studied by susceptibility and Moessbauer measurements. It is found that iron in the system is partially inverted, with ∼80% high-spin Fe2+ iron at octahedral sites. AC susceptibility data show a spin-glass-like transition at TSG=10 K that depends on the driving frequency f, following a Vogel-Fulcher law. Below TSG, the splitting of Zeeman levels yields a complex Moessbauer spectrum, which was fitted using a full 57Fe-nuclear Hamiltonian with quadrupolar and magnetic interactions. The reduced magnetic hyperfine field b(T)=B(T)/BS is well described by a Langevin function L(x), with TC=12.8(3) K and BS=16.8(3) T