Doping an antiferromagnetic insulator: A route to an antiferromagnetic metallic phase

Abstract

We have explored doping electrons into an antiferromagnetic (AFM) insulator as a route to realizing an AFM metal within a multiband Hubbard model. Considering parameters relevant for a 5d transition metal oxide with a half-filled t2g band we find that an AFM metallic phase is stabilized for occupancies up to 3.375 electrons per transition metal site for values of U up to 1.75 eV. At higher values of U, one has a charge-ordered insulating state. In contrast, the large Hund coupling associated with the 3d transition metal oxides does not allow for an AFM metallic phase for the concentrations examined. One has a ferromagnetic metallic phase for the 3d oxide for small values of U at 25% doping, however, at large values, one again finds charge ordering. Orbital degeneracy is found to play an important role, introducing the charge-ordered insulating phase into the phase diagram.