Magnetoelectric resonance with electromagnons in a perovskite helimagnet

Abstract

Maxwell's equations describe the interrelation between temporally changing electric (E) and magnetic (H) fields in a given medium. In materials that exhibit relativistic spin-orbit interactions, we also expect their polarization (P) and magnetization (M) to be dynamically coupled. This in turn could enable greater control over the cross-coupling between the electric and magnetic fields of light in the development of photonic devices. Such magnetoelectric phenomena are expected to be enhanced within materials that support electromagnons- fundamental excitations that exhibit both electric and magnetic dipole moments. Here we report the discovery of electromagnons in the perovskite (Eu,Y)MnO 3, which arise from fluctuations in the spontaneous polarization generated by cycloidal spin order. The resulting dynamical M-P cross-coupling causes the material to exhibit colossal directional dichroism-a difference in the absorption of light propagating in opposite directions-at the resonance frequency (sub-THz) associated with these excitations. © 2012 Macmillan Publishers Limited. All rights reserved.