Ferromagnetism of Transition-Metal Alloys

Abstract

By extending Anderson's model for a single impurity in a metal to the case of a finite concentration of impurities, the electronic structure and the electron interaction in transition-metal alloys are studied. The local-environment effect in the impurity magnetization first discussed by Jaccarino and Walker can be reasonably explained by accounting for the local modification of the electronic structure of the host metal due to the other surrounding impurities. In alloys such as Ni in Pd, where in the low-concentration limit the Ni impurity does not have a localized moment and the alloy system is not ferromagnetic, we examine how, as we increase the impurity concentration, the total ferromagnetism of the alloy is produced. If the interactions among the impurities, between the impurities and the host metal, and among the host-metal electrons are properly taken into account, the Friedel-Anderson-Wolff condition for the occurrence of the localized magnetic moment on an impurity exactly coincides with the condition for the onset of ferromagnetism of the entire system. Various magnetic properties of transition-metal alloys are discussed, taking into account the simultaneous modifications of electronic structure and electron interaction due to the presence of impurities.