Moessbauer and magnetization studies of the cubic NpPdsub(3-x)Rhsub(x) intermetallic compounds

Susceptibility and Moessbauer absorption studies of 237Np in the cubic Nsub(p)Pdsub(3-x)Rhsub(x) (0 <= x <= 3) intermetallic compounds were performed. The results show a decrease of the ordering temperature as a function of x (for x = 0.0, 0.1, 0.25, Tsub(N) = 50, 27, 15 K respectively), a decrease of the paramagnetic effective moment and a large increase of the magnetic hyperfine field acting on the Np nucleus (μsub(eff) = 2.7μsub(B), Hsub(eff) = 3.3 mOe for NpPd3, and μsub(eff) = 1.9μsub(B), Hsub(eff) = 4.8 mOe for NpPdsub(2.75)Rhsub(0.25). This unusual magnetic behaviour indicates that in the NpM3 systems there is no simple relation between the hyperfine field and the magnetic moment. The magnetic properties are mainly determined by the M component and the corresponding band structure. (author)