Spin-glass behavior in iron-aluminum alloys: A microscopic model

Abstract

Drawing upon a model of Sato and Arrott, it is proposed that the spin-glass behavior observed in iron-rich ${\mathrm{Fe}}_{1-x}{\mathrm{Al}}_x$ alloys arises by virtue of competition between a nearest-neighbor Fe—Fe ferromagnetic exchange $J$ and a further-neighbor Fe—Al—Fe antiferromagnetic superexchange $-\alpha J$. The special crystal structure of these alloys makes possible a mapping (decimation) of this model onto a simple-cubic magnet with random exchange. Previous approximate solutions of the simple-cubic model may then be used to construct the ${\mathrm{Fe}}_{1-x}{\mathrm{Al}}_x$ magnetic phase diagram. For an appropriately chosen ratio $\alpha$ (antiferro/ferro), an acceptable fit to the experimental phase diagram is obtained.