Range of validity of the simple alloy model for magnetism in transition metals

The range of validity of the simple alloy model for magnetism in transition metals is studied. By assuming that the local magnetic moments point up or down along a given direction, we analyzed the stability of configurations with various degrees of magnetic order, i.e., from the perfect ferromagnet to the paramagnetic disordered moment state. The electronic structure is solved within the coherent-potential approximation and for two different model density of states. In particular, results are presented for the behavior of the magnetic moments, the magnetic phase diagram, and the Curie temperature. The shortcomings of the alloy model are discussed by comparison with Hubbard's recent theory of magnetism. It is shown how to extend the simple-alloy-model theory to include the important magnetic moment fluctuations taken into account by Hubbard.