Occurrence of Local Moments and Ferromagnetism in Dilute Alloys

Abstract

In this paper we discuss some basic theoretical aspects of the magnetism of random dilute alloys, starting with the Anderson model. First, we determine how an impurity state is modified by the presence of the other impurities in its neighborhood. Even if we consider only one species of im-purity atoms, the electronic state at each impurity site is different depending upon the distribution of other impur-ities in its local environment. Second, we discuss a general relation between the occurrence of a local moment on an individual impurity and the ferromagnetic ordering of the total impurity spins. Finally, we discuss the magnetic interaction between the impurities. Especially in the case of direct transfer interaction, we show that the interaction between impurities can be either ferromagnetic or antiferro-magnetic depending upon the fractional occupation of the impurity states.

Supported by the National Science Foundation.