Magnetization and susceptibility of disordered alloy with competitive interactions

A model calculation of magnetization and susceptibility of disordered alloy (A _pB_{1 −p} ) where bothA andB represent the magnetic atoms is presented. It is based on the cluster-variational method where interactions within the clusters of all possible configurations are treated exactly and the rest of the interaction is replaced by an effective variational field. The frustration effect is introduced taking the exchange interactionsJ _AB orJ _BB or both to be antiferromagnetic whereas the exchangeJ _AA is ferromagnetic. The results are qualitatively similar to the observed behaviour of moment and susceptibility in some metallic glasses. The critical concentration for ferromagnetic state is determined in the presence of competitive interactions.