ITINERANT FERROMAGNETISM OF THE MULTIBAND HUBBARD-MODEL

We present some exact studies on the ferromagnetic ground state of the multiband Hubbard models including the periodic Anderson model (two-b and) and CuO2 plane in the oxide superconductors (three band). First w e show rigorous arguments that the ground state of the periodic Anders on model contains a ferromagnetic phase with spin angular momentum S = (N-1)/2 for Ne = N+1 where N is the number of lattice sites and Ne is that of electrons. Secondly the exact diagonalization technique is ap plied to small clusters. The models have the phase with high-spin stat e, indicating that a conduction electron is moving in the ferromagneti c background of localized spins.