Magnetoelastic distortion of multiferroic BiFeO3 in the canted antiferromagnetic state

Abstract

Using THz spectroscopy, we show that the spin-wave spectrum of multiferroic BiFeO3 in its high-field canted antiferromagnetic state is well described by a spin model that violates rhombohedral symmetry. We demonstrate that the monoclinic distortion of the canted antiferromagnetic state is induced by the single-ion magnetoelastic coupling between the lattice and the two nearly antiparallel spins. The revised spin model for BiFeO3 contains two new single-ion anisotropy terms that violate rhombohedral symmetry and depend on the direction of the magnetic field.