Abstract
We propose a model for the pair of electromagnon excitations observed in the class of multiferroic materials ( 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 has an oscillatory polarization with amplitude 50 times larger than its uniform polarization.
- Received 16 June 2009
DOI:https://doi.org/10.1103/PhysRevB.80.094419
©2009 American Physical Society