Neutron powder diffraction study of the crystal and magnetic structures of Fe2SiS4

The orthorhombic Fe2SiS4 (space group no. 62, Pnma) showing olivine-type structure has been studied. Measurements using neutron powder diffraction experiments were performed at 295, 140, 120, 40, 20 and 10 K in order to determine 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 at 30 K the appearance of a ferrimagnetic (Fi) state is observed. Different magnetic models are presented. Relations are found between indirect magnetic interactions, on the one hand, and the Fe(4a), Fe(4c) and sulfur positions, on the other hand, and relations between the crystal structure and the magnetic models are given. The neutron powder diffraction results are compared with results, already reported, of Mossbauer and magnetization measurements. (C) 1999 Elsevier Science B.V. All rights reserved.