title: Giant Spin-Driven Ferroelectric Polarization in BiFeO₃ at Room Temperature.
abstract: The spin-driven polarizations of type-I multiferroics are veiled by the preexisting ferroelectric (FE) polarization. Using first-principles calculations combined with a spin model, we uncover two hidden but huge spin-driven polarizations in the room-temperature multiferroic BiFeO(3). One is associated with the global inversion symmetry broken by a FE distortion, and the other is associated with the local inversion symmetry broken by an antiferrodistortive octahedral rotation. Comparison with recent neutron scatterings reveals tha first polarization reaches ∼3.0  μC/cm(2), which is larger than in any other multiferroic material. Our exhaustive study paves a way to uncover the various magnetoelectric couplings that generate hidden spin-driven polarizations in other type-I multiferroics.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Randy S
authors.initials: RS
authors.lastname: Fishman