Analysis of Magnetic Interactions in Alloys of Platinum with Iron Group Transition Elements

Abstract

The magnetic properties of alloys of platinum with iron group transition elements are analyzed and interpreted on the basis of an Ising model of ferromagnetism. It is found that in the wide ranges of compositions of the face-centered-cubic alloys of Ni, Co, Fe, Mn, and Cr with Pt there is systematic change with atomic number in the dependence of Curie temperature and saturation magnetization on concentration of magnetic atoms or on the formation of superlattices. Values of magnetic interactions in alloys, which also depend on the concentration, are estimated mainly from the Curie point by using the Cluster-Variation method. The magnetic moment of Pt atoms can be induced in alloys and this tendency becomes stronger as the d-shell radii of magnetic atoms increase. The analysis also indicates that the magnetic interactions of γ-Fe, γ-Mn and f.c.c. Cr change their signs from negative to positive by merely increasing the interatomic distance. This is most clearly shown in the case of γ-Fe. Further, it is suggested that the alloys Mn-Pt and Cr-Pt would show ferrimagnetic behavior as found in disordered Ni-Mn alloys. Based upon such analyses, a qualitative conclusion concerning the dependence of magnetic interactions upon distance is drawn. The general behavior of the interaction is consistent with the generally accepted picture of the location of these elements with respect to the “Bethe-Slater curve” of exchange interactions if the distances are short, but not if the distances are longer.