High-field magnetization in transuranium compound

Abstract We measured the high-field magnetization up to 55 T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa 5 with the tetragonal structure. The magnetization at 4.2 K for H ∥ [ 1 0 0 ] indicates a sharp metamagnetic transition with a step at H c = 26 T and saturates above H s = 38 T , reaching 0.43 μ B / Np . An ordered moment of 0.96 μ B / Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43 μ B / Np at H s , together with an orientation of the magnetic moment from the (0 0 1) plane to the (1 0 0) plane.