Evidence for an electromagnon in GdMn 2 O 5 : A multiferroic with a large electric polarization

We report in this paper the dynamical properties of ${\mathrm{GdMn}}_{2}{\mathrm{O}}_{5}$ studied by inelastic neutron scattering and infrared spectroscopy assisted by ab initio calculations. Our work sheds light on the electromagnon, a magnetic mode that can be excited by an electric field. Combining spin-wave measurements, simulations, and ab initio calculations of the single-ion anisotropies and the superexchange interactions, we describe in detail the magnetic contribution to this mode. An exhaustive study of the temperature and polarization dependence of its electroactivity completes this comprehensive study of the complex ${\mathrm{GdMn}}_{2}{\mathrm{O}}_{5}$ system.