Local magnetic behavior of Rh in Ni-Rh alloys: An experimental and theoretical study

• Published in: Physical review. B, Condensed matter Condensed matter, 1994-03, Vol.49 (10), p.6726-6735
• Main Authors: Krishnamurthy, VV, Mishra, SN, Press, MR, Paulose, PL, Devare, SH, Devare, HG
• Format: Article
• Language: English
• ISSN: 0163-1829; 1095-3795
• DOI: 10.1103/PhysRevB.49.6726

Magnetic behavior of Rh in paramagnetic Ni sub x Rh sub 1-x for x < =0.63 was studied by measuring the exp 100 Rh local susceptibility using the time-differential perturbed-angular-correlations method, the bulk magnetization, and local-spin-density calculations. For xapprox0.6 the measured Curie-Weiss local susceptibility yielded a high Rh magnetic moment with a small spin fluctuation temperature < =100K, while for x < =0.40 the observed results were consistent with an unstable moment on Rh characterized by large spin-fluctuation temperatures approx10 exp 3 K. The magnetism of Rh in the Ni-Rh system was found to depend on the number of Ni atoms in its immediate surrounding. The calculations show that both Ni and Rh atoms acquire moments in the presence of at least two Ni atoms in the nearest-neighbor (NN) coordination shell. Further, Ni and Rh moments were 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. The experimental results, as well as theoretical calculations, show that Rh magnetic behavior is strongly influenced by the sign of the interatomic exchange interaction. In particular, the observed enhanced Rh magnetic response near xapprox0.6 is attributed to the ferromagnetic d-d interaction between Rh and Ni atoms.