Electromagnon and phonon excitations in multiferroic TbMnO3

TL;DR

This study investigates electromagnon and phonon excitations in TbMnO3 using Raman spectroscopy, revealing how magnetic field-induced spin spiral flips and specific interactions influence multiferroic properties and phonon behavior.

Contribution

The paper reports the first observation of electromagnons created by Dzyaloshinskii-Moriya interaction in TbMnO3 and identifies phonon modes linked to ferroelectric transition.

Findings

Electromagnons are induced by spin spiral plane flips.

Dzyaloshinskii-Moriya interaction creates electromagnons along the c axis.

One phonon mode is sensitive to the ferroelectric transition.

Abstract

We have performed Raman measurements on TbMnO3 single crystal under magnetic field along the three crystallographic directions. The flip of the spin spiral plane creates an electromagnon excitation. In addition to the electromagnons induced by the Heisenberg coupling, we have detected the electromagnon created by the Dzyaloshinskii-Moriya interaction along the c axis. We have identified all the vibrational modes of TbMnO3. Their temperature dependences show that only one phonon observed along the polarization axis is sensitive to the ferroelectric transition. This mode is tied to the Tb3+ ion displacements that contribute to the ferroelectric polarization.