Neutron and magnetization studies of the UP-US system

Solid solutions exist for $0\le x\le 1$ in the system ${\mathrm{UP}}_{1-x}{\mathrm{S}}_x$. 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 $0.10\le x\le 0.20$. For $x=0.1\mathrm{}$ the initial magnetic structure ($T_N=98\mathrm{}$°K) is type $\mathrm{IA}$; at ∼ 85°K this transforms to the type-I structure, but at ∼ 50°K the structure reverts to the $\mathrm{IA}$. Bulk-magnetization experiments show that the material is meta-magnetic during the high-temperature $\mathrm{IA}$-I transition. The induced ferromagnetic moment has been examined by measuring the depolarization of polarized neutrons transmitted through the sample. For $x=0.15\mathrm{}$ the magnetic structure is type $\mathrm{IA}$ at all temperatures below $T_N$. For $x=0.20\mathrm{}$ an additional phase, with a 3 + 3,—configuration, coexists with the type-$\mathrm{IA}$ phase between 40 and 80°K. Large peaks in the magnetization are also observed just below $T_N$ for the $x=0.15\mathrm{} \mathrm{and} 0.20$ compositions.