Ferromagnetism in orbitally degenerate Hubbard model

The effect of orbital degeneracy on metallic ferromagnetism is considered in the strong coupling limit of the Hubbard model within a generalized Roth approximation. For concentrations of less than one electron per lattice site we find that orbital degeneracy favors magnetic polarization on different lattice structures. The effect is strong enough to induce a ferromagnetic ordering even on frustrated lattices, where polarization is excluded in absence of degeneracy. We comment on the physical origin of the results in terms of competition between delocalization and localization tendencies. (c) 2005 Elsevier B.V. All rights reserved.