Origin of electromagnon excitations in \textit{R}MnO$_3$
  The origin of electromagnon excitations in cycloidal \textit{R}MnO$_3$ is explained in terms of the Heisenberg coupling between spins despite the fact that the static polarization arises from the much weaker Dzyaloshinskii-Moriya (DM) exchange interaction. We present a model that incorporates structural characteristics of this family of manganites that is confirmed by far infrared transmission data as a function of temperature and magnetic field and inelastic neutron scattering results. A deep connection is found between the magnetoelectric dynamics of the spiral phase and the static magnetoelectric coupling in the collinear E-phase of this family of manganites. 
R. Vald\'es Aguilar, M. Mostovoy, A. B. Sushkov, C. L. Zhang, Y. J.   Choi, S-W. Cheong and H. D. Drew