Observation of Magnetic and Structural Phase Transition in CsFeS2

Abstract

Both neutron diffraction and Mössbauer investigation reveal that CsFeS 2 remains paramagnetic down to 70 K, at which a sudden first order magnetic and structural phase transition takes place. Antiferromagnetic coupling of spins both along the c -axis and along the diagonal direction in the a - b plane of the orthorhombic crystal structure of the high temperature phase accounts best for the observed low temperature neutron diffraction data. Mössbauer parameters determined over the temperature range from 4.2 K to room temperature indicate that the iron in CsFeS 2 is in a ferric state having large covalent bonding to sulfur ligands. The measured hyperfine field of 193.0±0.1 kOe at 4.2 K is a quite reduced value compared with those of other high spin ferric compounds.