Field and temperature dependence of electromagnon scattering in TbMnO_3 studied by inelastic neutron scattering

摘要

Inelastic neutron scattering techniques have been used to study the field-induced multiferroic transition and the temperature dependence of magnetic excitations in TbMnO_3. The significant changes in the spin-wave spectra across the field-induced transition perfectly agree with a rotation of the cycloidal spiral plane and with efficient pinning in the commensurate high-field phase. Further analysis of the Q dependence allows the identification of an electromagnon in the multiferroic high-field phase whose energy and polarization precisely matches previous infrared data. This and the zero-field temperature dependence of a zone-center magnon, which exactly agrees with that of an optically detected excitation, document that the inverse Dzyaloshinskii-Moriya interaction induces an electromagnon hybrid excitation in TbMnO_3.