Magneto-electric excitations in multiferroic TbMnO3 by Raman scattering

TL;DR

This study uses Raman spectroscopy to investigate low energy excitations in multiferroic TbMnO3, revealing magnetoelectric excitations called electromagnons with distinct selection rules, enhancing understanding of multiferroic excitations.

Contribution

It reports the observation of electromagnons in TbMnO3 via Raman scattering, highlighting their magnetoelectric nature and differing selection rules from previous infrared measurements.

Findings

Two peaks at 30 cm-1 and 60 cm-1 observed in the cycloidal phase.

Peaks show different selection rules compared to previous infrared data.

Electromagnons are confirmed as magnetoelectric excitations.

Abstract

Low energy excitations in the multiferroic material TbMnO3 have been investigated by Raman spectroscopy. Our observations reveal the existence of two peaks at 30 cm-1 and 60 cm-1. They are observed in the cycloidal phase below the Curie temperature but not in the sinusoidal phase, suggesting their magnetoelectric origin. While the peak energies coincide with the frequencies of electromagnons measured previously by transmission spectroscopy, they show surprisingly different selection rules, with the 30 cm-1 excitation enhanced by the electric field of light along the spontaneous polarization. The origins of the modes are discussed under Raman and infrared selection rules considerations.