Spin-Phonon Coupling, High Pressure Phase Transitions and Thermal Expansion of Multiferroic GaFeO3: A Combined First Principles and Inelastic Neutron Scattering Study

TL;DR

This study combines first principles calculations and inelastic neutron scattering to explore the phonon behavior, phase stability, and thermal expansion of multiferroic GaFeO3 under various conditions, revealing the critical role of magnetism.

Contribution

It provides a comprehensive analysis of spin-phonon coupling, high pressure phase transitions, and thermal expansion in GaFeO3 using combined experimental and theoretical approaches.

Findings

Magnetism significantly influences phonon spectra and structural stability.

High pressure phases of GaFeO3 are characterized by enthalpy calculations.

Thermal expansion behavior is linked to phonon volume dependence.

Abstract

We have carried out an extensive phonon study on multiferroic GaFeO3 to elucidate its dynamical behavior. Inelastic neutron scattering measurements are performed over a wide temperature range, 150 to 1198 K. First principles lattice dynamical calculations are done for the sake of the analysis and interpretation of the observations. The comparison of the phonon spectra from magnetic and non-magnetic calculations highlights pronounced differences. The energy range of the vibrational atomistic contributions of the Fe and O ions are found to differ significantly in the two calculation types. Therefore, magnetism induced by the active spin degrees of freedom of Fe cations plays a key role in stabilizing the structure and dynamics of GaFeO3. Moreover, the computed enthalpy in various phases of GaFeO3 is used to gain deeper insights into the high pressure phase stability of this material. Further, the volume dependence of the phonon spectra is used to determine its thermal expansion behavior.