Magnetization of Localized States in Metals

Abstract

A study has been made of the magnetic properties of dilute solutions of iron in various nonmagnetic 4d series elements and alloys. In some cases the iron atoms possess a localized magnetic moment which manifests itself as an inverse temperature dependence in the susceptibility of the solution. The occurrence of the moment is determined by the valence electron concentration in the solute element (or alloy). As a function of this quantity one finds portions of the 4d series in which localized moments are strictly absent, interspersed by regions—one centered near Mo, the other in the vicinity of Rh and Pd—in which magnetization occurs and at whose edges the moments appear almost discontinuously. This behavior may be understood in terms of a theoretical model in which the magnetization is ascribed to a virtual level, of the type proposed by Friedel, of the iron atom. Polarization occurs when the virtual level lies near the Fermi level and is sufficiently sharp in energy. A self-consistent Hartree-Fock calculation indicates that under these circumstances the impurity atom develops an exchange potential which splits the level—causing it to have different energies for spin-up and spin-down electrons and thus giving rise to magnetization. The model gives a qualitative description of the experiments and, in particular, is able to account for the fact that the impurity atoms sometimes carry a moment that is a fraction of a Bohr magneton.