Electron Correlation in Ferromagnetism. II. Hybridization ofsanddBands

The problem of electron correlation in the ferromagnetism of transition metals is investigated by taking an approximate model Hamiltonian which takes into account the hybridization of the $s$ and $d$ bands. The Green's-function technique is used to obtain the self-consistent ferromagnetic solutions within the Hartree-Fock approximation. An approximate solution of the correlation problem is obtained. The ferromagnetic solutions for which the correlation effects are taken into account are compared with those in the Hartree-Fock approximation. The model is used to investigate the role of the $s-d$ interaction in metal-nonmetal transitions. It is also possible to understand the difficulty of observing pressure-induced nonmetal-metal transition.