LOCAL MAGNETIC-BEHAVIOR OF RH IN NI-RH ALLOYS - AN EXPERIMENTAL AND THEORETICAL-STUDY

Magnetic behavior of Rh in paramagnetic NixRh1-x for x less-than-or-eq ual-to 0.63 is studied by measuring the Rh-100 local susceptibility us ing the time-differential perturbed-angular-correlations method, the b ulk magnetization, and through local-spin-density calculations. For x approximately 0.6 the measured Curie-Weiss local susceptibility yields a high Rh magnetic moment with a small spin-fluctuation temperature l ess-than-or-equal-to 100 K, while for x less than or similar to 0.40 t he observed results are consistent with an unstable moment on Rh chara cterized by large spin-fluctuation temperatures approximately 10(3) K. The magnetism of Rh in the Ni-Rh system is found to depend on the num ber of Ni atoms in its immediate surrounding. The calculations show th at both Ni and Rh atoms acquire moments in the presence of at least tw o Ni atoms in the nearest-neighbor (NN) coordination shell. Further, N i and Rh moments are found to depend on the geometrical arrangement of the NN Ni atoms. The increase in the moment value on individual atoms and the enhanced susceptibility comes from the growing proportion of three-dimensional or isotropic NN Ni configurations over the linear or planar configurations, which occur for 5-6 or more Ni atoms. Our expe rimental results, as well as theoretical calculations, show that Rh ma gnetic behavior is strongly influenced by the sip of the interatomic e xchange interaction. In particular, the observed enhanced Rh magnetic response near x approximately 0.6 is attributed to the ferromagnetic d -d interaction between Rh and Ni atoms.