MAGNETIC-PROPERTIES OF NEPTUNIUM AND PLUTONIUM HYDRIDES

The magnetic susceptibility and magnetization of NpHx and PuHx (2.0≤x≤3.0) compounds have been measured between 4 and 700 K. The susceptibility of the NpHx compounds is weakly temperature dependent and a crystal-field calculation based on the 5f4(Np3+) ground-state configuration was in reasonable agreement with the experimental results for the dihydride (cubic CaF2-type structure). The cubic plutonium dihydride has a susceptibility maximum, indicative of antiferromagnetic ordering, at 30 K. Cubic plutonium compounds with higher hydrogen concentrations order ferromagnetically with transition temperatures that increase with an increase in x and reach a maximum of 66 K at x=2.7. The hexagonal plutonium trihydride becomes ferromagnetic at 101 K. Although the details of the ordering scheme and a complete crystal-field calculation await a neutron-scattering study, it appears that the most likely ground-state configuration is 5f5(Pu3+). © 1979 The American Physical Society.