Electron correlation in the narrow-band model for disordered ferromagnetic alloys

Publisher Website
Google Scholar
Abstract
The ferromagnetism of a random disordered substitutional binary alloy described by the narrow-energy-band model of Hubbard is discussed within the framework of the coherent-potential approximation with strong correlation effects included. The treatment of Coulomb correlations used is an improved version of the first Hubbard approximation which seems to adequately describe those correlation effects that have a major influence on the stability of the ferromagnetic phase for large intra-atomic Coulomb repulsion. Disorder is considered in the site-diagonal terms of the Hubbard model. Numerical illustrations are presented which describe the ferromagnetic solutions in terms of the component magnetizations and component densities of states as functions of electron concentration in the band for several cases of disorder and alloy compositions. In these examples the intra-atomic Coulomb repulsion is assumed to be infinite. Comparisons are made with results obtained using a Coulomb repulsion of the order of the bandwidth treated by the Hartree-Fock approximation. One finds that results are qualitatively similar for small electron concentrations and the examples detail the differences at larger concentrations. Finally a brief discussion with respect to experiment is made.