Evidence of electro-active excitation of the spin cycloid in TbMnO3

TL;DR

This study investigates terahertz excitations in TbMnO3, revealing an electro-active mode associated with the spin cycloid, supporting the inverse Dzyaloshinskii-Moriya mechanism of magnetoelectric coupling.

Contribution

It provides experimental evidence of an electro-active excitation of the spin cycloid in TbMnO3, confirming theoretical predictions.

Findings

Identification of an electro-active excitation along the c-axis

Support for the inverse Dzyaloshinskii-Moriya mechanism

Observation of field-induced magnetic transition effects

Abstract

Terahertz electromagnetic excitations in the multiferroic TbMnO3 at the field-induced magnetic transition are investigated for different orientations of the magnetic cycloid. In addition to the electromagnon along the a-axis, the detailed polarization analysis of the experimental spectra suggests the existence of an electro-active excitation for ac electric fields along the crystallographic c-axis. This excitation is possibly the electro-active eigenmode of the spin cycloid in TbMnO3, which has been predicted within the inverse Dzyaloshinskii-Moriya mechanism of magnetoelectric coupling.