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.