Enhanced Effective Exchange Interaction due to Localized Spins in Dilute Alloys and Rare Earth Metals

Abstract

An effective interaction between conduction electrons is obtained by eliminating the exchange interaction between conduction electrons and localized spins in metals both in the paramagnetic and spin-ordered state. In the paramagnetic state the effective electron interaction is mediated by the flipping motion of the localized spin under the action of the local field and the electron interaction derived is of an exchange type and repulsive in the vicinity of the Fermi surface. On this basis we show that the observed ferromagnetism in dilute alloys like Fe in Pd may be understood from the large enhancement of conduction-electron susceptibility. In the spin-ordered state, such as rare-earth metals below the Curie temperature, the effective electron interaction arises from the exchange of spin waves between electrons. The electron interaction obtained is of a form of repulsion between electrons of opposite spins at the same atomic site in the vicinity of the Fermi surface. The electron self-energy due to this effective electron interaction is calculated for a simplified model and we discuss the possibility of an appreciable enhancement of the electronic specific heat in rare earth metals.