Model for twin electromagnons and magnetically induced oscillatory polarization in multiferroic RMnO${}_3$

Abstract

We propose a model for the pair of electromagnon excitations observed in the class of multiferroic materials {\it R}MnO${}_3$ ({\it R} is a rare-earth ion). The model is based on a harmonic cycloid ground state interacting with a zone-edge magnon and its twin excitation separated in momentum space by two times the cycloid wave vector. The pair of electromagnons is activated by cross coupling between magnetostriction and spin-orbit interactions. Remarkably, the spectral weight of the twin electromagnon is directly related to the presence of a magnetically induced oscillatory polarization in the ground state. This leads to the surprising prediction that TbMnO${}_3$ has an oscillatory polarization with amplitude 50 times larger than its uniform polarization.

4 pages, 3 figures

References in corpus (5)

• Spin current and magneto-electric effect in non-collinear magnets
• Role of the Dzyaloshinskii-Moriya interaction in multiferroic perovskites
• Origin of electromagnon excitations in \textit{R}MnO${}_3$
• Optical coupling to spin waves in the cycloidal multiferroic BiFeO3
• Magnetic and magnetoelectric excitations in TbMnO${}_3$