Neutron powder diffraction study of the crystal and magnetic structures ofFe2SiS4

The orthorhombic Fe2SiS4 (space group no. 62, Pnma) showing olivine-type st ructure has been studied. Measurements using neutron powder diffraction exp eriments were performed at 295, 140, 120, 40, 20 and 10 K in order to deter mine the crystal and magnetic structures of Fe2SiS4 at low temperatures. No crystallographic phase transition was observed between 295 and 10 K while two magnetic transitions were found. One transition around 127 K denotes a change from the paramagnetic (P) to an antiferromagnetic (AF) state while a t 30 K the appearance of a ferrimagnetic (Fi) state is observed. Different magnetic models are presented. Relations are found between indirect magneti c interactions, on the one hand, and the Fe(4a), Fe(4c) and sulfur position s, on the other hand, and relations between the crystal structure and the m agnetic models are given. The neutron powder diffraction results are compar ed with results, already reported, of Mossbauer and magnetization measureme nts. (C) 1999 Elsevier Science B.V. All rights reserved.