IR Phonon signatures of multiferroicity in TbMn$_{2}$O$_{5}$

TL;DR

This study investigates how infrared-active phonons in multiferroic TbMn2O5 change with temperature, revealing phonon behavior linked to magnetic and ferroelectric phase transitions and providing insights into lattice distortions.

Contribution

It demonstrates the correlation between IR phonon modes and phase transitions in TbMn2O5, highlighting a phonon mode as a sensitive probe of ferroelectric symmetry breaking.

Findings

IR phonons are observed along a and b axes.

A high-frequency b-polarized phonon becomes IR active at ferroelectric transition.

The IR strength of this mode correlates with the ferroelectric order parameter.

Abstract

The infrared (IR) active phonons in multiferroic TbMn$_2$O$_5$ are studied as a function of temperature. Most of the symmetry allowed IR modes polarized along the \textit{a} and \textit{b} crystal axes are observed and the behavior of several \textit{b} polarized phonons is correlated with the magnetic and ferroelectric transitions. A high frequency \textit{b} polarized phonon only Raman allowed in the paraelectric phase becomes IR active at the ferroelectric transition. The IR strength of this mode is proportional to the square of the ferroelectric order parameter and gives a sensitive measure of the symmetry lowering lattice distortions in the ferroelectric phase.