Neutron and magnetization studies of the UP-US system

Solid solutions exist for 0≤x≤1 in the system UP₁₋ₓSₓ. All compositions are cubic at room temperature with the NaCl crystal structure. The results of neutron-diffraction and bulk-magnetization measurements on a number of compositions are reported, with particular emphasis on the region 0.10≤x≤0.20. For x=0.1 the initial magnetic structure (T_N=98°K) is type IA; at 85°K this transforms to the type-I structure, but at 50°K the structure reverts to the IA. Bulk-magnetization experiments show that the material is meta-magnetic during the high-temperature IA-I transition. The induced ferromagnetic moment has been examined by measuring the depolarization of polarized neutrons transmitted through the sample. For x=0.15 the magnetic structure is type IA at all temperatures below T_N. For x=0.20 an additional phase, with a 3 + 3,---configuration, coexists with the type-IA phase between 40 and 80°K. Large peaks in the magnetization are also observed just below T_N for the x=0.15 and 0.20 compositions.