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

Drawing upon a model of Sato and Arrott, it is proposed that the spin-glass behavior observed in iron-rich Fe_1-xAlₓ alloys arises by virtue of competition between a nearest-neighbor Fe---Fe ferromagnetic exchange J and a further-neighbor Fe---Al---Fe antiferromagnetic superexchange -αJ. 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 Fe_1-xAlₓ magnetic phase diagram. For an appropriately chosen ratio α (antiferro/ferro), an acceptable fit to the experimental phase diagram is obtained.