Statistical Mechanical Theory of a Random Ferromagnetic System

Abstract

The behavior of solid solutions of paramagnetic impurities which are exchange coupled in a nonmagnetic substrate turns out to yield a considerable body of information with regard to the nature of the exchange coupling as well as detailed temperature dependence of the spin system. In the present paper, a rigorous expansion of the mean free energy averaged over random sites is presented. It is shown that a ferromagnetic phase transition does occur. The Curie point is given as a function of concentration for the case of weak dilution in an implicit power series form.