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 BiFeO3. 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 octahedra rotation. Comparison with recent neutron scatterings reveals that first polarization reaches 3.0 μC/cm2, 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.
@article{arxiv.1504.07106,
title = {Huge Spin-Driven Polarizations at Room-Temperature in bulk BiFeO3},
author = {Jun Hee Lee and Randy S. Fishman},
journal= {arXiv preprint arXiv:1504.07106},
year = {2015}
}