  Ferroelectricity-the switchable intrinsic electric polarization-has not yet
been attained in a metal experimentally and is in fact generally deemed
irreconcilable with free carriers, although polar metal has been achieved
recently. Multiferroic metal has never even been proposed though multiferroics
have been widely investigated. Here we report a room-temperature coexistence of
multiferroicity and metallic behavior in PbNb0.12Ti0.88O3-delta films. The
oxygen-vacancy-induced electrons become delocalized and ameliorate the
ferromagnetic properties of these films, whereas they fail to vanish the polar
displacements nor the individual dipole in each unit cell. This concurrent
appearance of multiferroicity and metallicity is also confirmed by our
first-principles calculation performed on 12.5% Nb-doped PbTiO3 with oxygen
vacancies. These findings break a path to multiferroic metallic materials and
offer a potential application for multiferroic spintronic devices.
