On the Disappearance of Ferromagnetism in Disordered Fe-Al Alloys

The magnetic properties of disordered Fe rich Fe-Al are investigated theoretically by using the coherent potential approximation (CPA) on the basis of the two different models. The self-consistent CPA calculation combined with the Korringa-Kohn-Rostoker method and the local spin density approximation is shown to reproduce the experimental result of the conceptration dependence of the bulk magnetization only for low Al concentration region. The ferromagnetism-to-spin glass second order transition at the critical Al concentration is obtained by the calculation on the basis of the tight binding model in which Fe atoms with magnetic moment antiparallel to the bulk magnetization are distinguished from Fe atoms with parallel moments. The calculated spin susceptibility well reproduces the experimental result.