The antiferromagnetic and ferrimagnetic properties of iron selenides with NiAs-type structure

摘要

The magnetic properties of the NiAs-type iron selenides have been investigated by susceptibility measurements between 100 and 450 K. Hexagonal γ-Fe1-xSe exhibits both antiferromagnetism and ferrimagnetism depending on composition. For antiferromagnetic alloys with 0.02≤x≤0.10 (50.5 to 52.5 at Se) the transition to the paramagnetic state is assumed to occur in the unstable range between room temperatur and about 573K. Ferrimagnetism is observed at compositions near Fe7Se8(0.10≤x≤0.16; 52.5 to 54.3 at Se) withCurietemperatures varying only slightly with composition. In Fe7Se8the ferriparamagnetic transition is observable at 453 K. The characteristic discontinuities in the magnetization curves of Fe7Se8in both superstructures (3c, 4c) are related to the rotation of the magnetic moments from a direction close to 001 in