Magnetic polarization in the Ramírez-Falicov model of valency change transitions: Application to cerium

The Ramírez-Falicov model of the $\alpha -\gamma$ phase transition of cerium is extended, allowing for a field-induced or spontaneous splitting of the bands and of the sixfold degenerate $4f$ level. The effect of presently available magnetic fields on the $\alpha -\gamma$ transition temperature in cerium is found to be negligible. With higher values (not appropriate to cerium) for the conduction-electron-$f$-electron exchange parameter, the model shows first- and second-order transitions to a ferromagnetic $\gamma$ phase. The resulting phase diagrams are discussed in terms of the magnetization behavior expected from a system described by the model.