Specific heat and magnetization in dilute magnetic alloys

Abstract

We have studied dilute alloys where interactions of the Ruderman-Kittel-Yosida type are assumed to exist between well-defined magnetic moments that are localized on impurities distributed at random in the matrix. Using a molecular field model, such as has been proposed by Blandin and Friedel, ¹² we show that, because of the geometrical characteristics of the interaction, simple correspondences are expected between the magnetic properties (specific heat and magnetization) of a given alloy for different values of the solute concentrationc. These quantities are expressed through concentration-independent functions of the “reduced temperature,”T/c, and the “reduced field,”h/c. The idea of “reduced diagrams,” where we plot both new and available data in terms ofT/c andh/c, follows from these functions. Generally good agreement is observed for the specific heat, the magnetization, the initial susceptibility, and the residual magnetization of a number of alloys. (The data used here are for theAu-Fe,Cu-Mn andAg-Mn systems.) Furthermore, discrepancies, due to other mechanisms, such as the Kondo effect, or the effect of a mean free path limitation may better appear in such diagrams.