T. Rõõm, J. Viirok, L. Peedu, U. Nagel, D. G. Farkas, D. Szaller, V. Kocsis, S. Bordács, István Kézsmárki, Dmytro Kamenskyi, H. Engelkamp, M. Ozerov, D. Smirnov, J. Krzystek, K. Thirunavukkuarasu, Y. Ozaki, Y. Tomioka, T. Ito, T. Datta, R. S. Fishman
- 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.