Theory of the coupling between conduction electrons and moments of 3d and 4f ions in metals

Abstract

The theory of the effective coupling between conduction electrons and the magnetic (or electric) moments of 3d and 4f ions in metals is reviewed, with emphasis on a systematic treatment of the generalized coupling forms which usually apply for real ions with orbital degrees of freedom. With the help of the irreducible-tensor method, the coupling is expanded in forms consistent with general symmetry requirements, and the effects of intra-ionic level structure of LS or LSJ type are taken into account. Coupling contributions from the direct and exchange parts of the Coulomb interaction between ionic and conduction electrons, and from the Anderson-Clogston-Schrieffer-Wolff virtual-mixing mechanism, are evaluated. The symmetry analysis is performed according to the full rotation group, meaning that the conduction band is represented as a free-electron band and effects of crystal-field splitting are not explicitly considered.