Electromagnons in multiferroic manganites

Abstract

We review terahertz experiments on magnetoelectric excitations in rare earth multiferroic manganites RMnO 3 with R = Gd, Tb, Dy, (Eu:Y).In all these compounds characteristic excitations of the novel type, called electromagnons, have been observed for frequencies 10 cm -1 < ν < 30 cm -1 .From the spectroscopic point of view electromagnons are responsible for the magnetoelectric effects in RMnO 3 and, contrary to magnons, are excited only by electric components of the electromagnetic wave.In all compositions the electromagnons appear as a broad Debye-like contribution in the sinusoidally modulated antiferromagnetic phase and transform to well-defined excitations as the magnetic structure becomes spiral.At the lowest temperatures the fine structure of electromagnons is observed, reflecting the increasing complexity of the magnetic structure.