Investigation of phonon dynamics of perovskite multiferroic manganites: RMnO3 (R=Tb, Dy, Ho)

TL;DR

This study uses a shell model to analyze phonon dynamics in RMnO3 multiferroic manganites, revealing phase coexistence and metastability, with results aligning well with experimental data.

Contribution

It provides a comprehensive theoretical analysis of phonon properties and phase stability in RMnO3 manganites, including phonon dispersion, density of states, and phase coexistence insights.

Findings

Phonon properties agree with experimental data

Zone-center imaginary Au mode indicates metastability

Orthorhombic and hexagonal phases may coexist

Abstract

We have used a shell model to study the phonon dynamics of multiferroic manganites RMnO3 (R= Tb, Dy, Ho). The calculated phonon dynamical properties, crystal structure, Raman frequencies and specific heat are found to be in good agreement with the available experimental data. Besides, the phonon density of states, elastic constants and phonon dispersion curves along high symmetry directions (sigma, delta and lambda) have also been computed. A zone-center imaginary Au mode is revealed in these phonon dispersion curves, which indicates the occurrence of metastability of the perovskite phase. The Gibbs free energy values of orthorhombic phase, when compared with those of hexagonal phase, indicate the possibility of coexistence of these two phases of these multiferroic manganites under ambient conditions.