Actinide pnictides and chalcogenides. IV. X-ray search for tetragonal distortion in UN and UAs in the antiferromagnetic state

Abstract

For pt. III, see abstr. A79114 of 1974. A single crystal of UN was studied at low temperatures by X-ray diffraction. Below the Neel temperature ( approximately 55K) a very small tetragonal distortion (c/a=0.99935 at 4.2K) of the NaCl-type lattice was observed, which is consistent with the tetragonal (type I) antiferromagnetic structure inferred from neutron diffraction. A small discontinuity in the lattice spacing of UAs was observed at the transition (around 60K) from type I to type IA antiferromagnetic ordering (at low temperatures).