Monte Carlo study of the transition from a ferromagnet to a spin glass in Fe-Al alloys

The transition from a ferromagnet to a spin glass in Fe-Al alloys as a function of Al concentration is studied by Monte Carlo methods. Following a model, initially proposed by Sato and Arrott, the spins on the Fe atom are assumed to interact via a direct ferromagnetic exchange between nearest neighbors and an antiferromagnetic superexchange between two Fe spins which are separated by an Al atom. These two interactions are sufficient to account qualitatively for the observed crossover from a ferrromagnet to a spin glass. This spin glass differs from the usual models, since the exchange constants are not random. Here the frustration arises only from the positional disorder of the Fe and Al atoms. © 1980 The American Physical Society.