57Fe Mössbauer absorption study in berthierite (FeSb2S4)

Abstract: The⁵⁷Fe isomer shift observed in FeSb₂S₄ indicates a rather ionic behaviour typical for high-spin Fe²⁺ ions. The N�el transition occurs at 50�1 K. The analysis of the complex M�ssbauer spectrum at 4.2 K supports the helicoidal magnetic structure with the magnetic moments in the (a, b) plane and with a non-commensurate propagation vector along thec axis. A sizeable anisotropy of the hyperfine field distribution is observed. The quadrupolar and magnetic hyperfine data are accounted for in the frame of a tetragonal crystal field approximation, which gives useful information on the single ion Fe²⁺ properties.