Antiferromagnetic order in NpRhGa5

NpRhGa5 develops anti ferromagnetic order below T-N = 37 K. Contrary to its NpCoGa3 counterpart. NpRhGa5 does not show any phase transition in applied magnetic fields up to 9 T, but undergoes a second magnetic transition-attributed to a reorientation of the magnetic moments from the c-axis to the basal plane-at T* = 32 K as evidenced by magnetization. resistivity. specific heat and Np-237 Mossbauer data. The latter also indicates the occurrence of a Np3+ charge state and an ordered Np moment of 0.96 mu(B). The comparison of the magnetic properties of NpRhGa5 and AnTGa(5) (An = U, Np, Pu; T = Co, Rh) compounds confirms that AnRhGa(5) and AnCoGa(5) are driven by common underlying physics and shows that magnetic interactions are enhanced in AnCoGa(5) compounds. suggesting a possible link with the enhanced superconductivity in PuCoGa5 compared to PuRhGa5. (C) 2004 Elsevier B.V. All rights reserved.