Characteristic High-Field Magnetization in a Transuranium Antiferromagnet NpRhGa₅

Abstract

We have measured the high-field magnetization for a transuranium antiferromagnet NpRhGa₅ with two successive antiferromagnetic transition temperatures of T_N1=36 and T_N2=32 K and an ordered moment of 0.96 μ_B/Np. For the magnetic field along the easy-axis of the [100] direction of the tetragonal structure, the magnetization indicates a metamagnetic transition at H_c=26 T with a sharp step and saturates above H_s=38 T, with 0.43 μ_B/Np. On the other hand, the hard-axis magnetization for H||[001] increases linearly and saturates above H_s=28 T, with 0.44 μ_B/Np. These magnetization curves were discussed on the basis of reorientation and reduction of the magnetic moment.