57Fe Mössbauer absorption study in berthierite (FeSb2S4)

The57Fe isomer shift observed in FeSb2S4 indicates a rather ionic behaviour typical for high-spin Fe2+ ions. The Neel transition occurs at 50±1 K. The analysis of the complex Mossbauer 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.