Magnetic structure and successive phase transition in NpRhGa5

Abstract The magnetic structure of NpRhGa 5 has been investigated by neutron scattering. NpRhGa 5 exhibits two antiferromagnetic phases with transition temperatures at T N 1 = 36 K and T N 2 = 33 K . Neutron diffraction experiments revealed an antiferromagnetic structure with a propagation vector q = ( 0 0 1 2 ) for both of the phases, where the Np magnetic moments are oriented along the tetragonal c -axis for T N 2 T T N 1 (AF1), and parallel to the [1 1 0] direction on the basal plane for T T N 2 (AF2). At T N 2 , the reorientation of magnetic moments is accompanied by a sudden increase of magnetic moments, indicative of the first order transition. The magnetic moment of Np is 0.96 ( 11 ) μ B at T = 3 K and 0.44 ( 16 ) μ B at T = 34 K . The magnetic form factor with | μ L / μ S | = 1.44 shows a dominant contribution of the orbital moment.