THEORY OF OPTICAL AND MAGNETOOPTICAL PROPERTIES OF INVAR COMPOUNDS

Abstract

The frequency-dependent optical conductivity tensor for ferromagnetic transition metal compounds is determined in a theoretical framework, in which spin-orbit interaction and ferromagnetic exchange interaction are included on an equal footing. The interplay of the latter two mechanisms manifests itself in substantial modifications of the diagonal tensor components and the appearance of offdiagonal components, and thereby in optical and magnetooptical properties. Numerical calculations for Fe₃Pt using a “high-spin” model yield a polar Kerr rotation angle in good agreement with experimental data, Results for the diagonal tensor components reveal very pronounced differences between assumed ”high-spin” and ”low-spin” models of Fe₃Pt. We conclude that specific experimental studies should be able to provide more information on the still not completely resolved issue of the nature of the INVAR mechanism in Fe₃Pt.