Correlation Effects on the Double Exchange Model in a Ferromagnetic Metallic Phase

The effect of the Hubbard interaction among conduction electrons on the double exchange model is investigated in a ferromagnetic metallic phase. Applying iterative perturbation theory to the Hubbard interaction within dynamical mean field theory, we calculate the one-particle spectral function and the optical conductivity, in which coherent-potential approximation is further used to treat the ferromagnetic Hund coupling between conduction electrons and localized spins. Identifying the decrease of the magnetization for the localized spin with the increase of the temperature, we discuss the temperature dependence of the one-particle spectrum and the optical conductivity. It is found that the interplay between the Hund coupling and the Hubbard interaction dramatically changes the spectral function, while it is somehow obscured in the optical conductivity.