Probing Magnetoelastic Coupling and Structural Changes in Magnetoelectric Gallium Ferrite

TL;DR

This study investigates the magnetoelastic coupling and structural stability of gallium ferrite across a wide temperature range, revealing no phase transition but identifying a significant change in spin-phonon interactions around 180 K.

Contribution

It provides detailed experimental evidence of spin-phonon coupling and its temperature-dependent behavior in gallium ferrite, highlighting a transition in spin dynamics without structural phase change.

Findings

No structural phase transition from 18 K to 700 K.

Discontinuity in Raman peak indicating spin-phonon coupling.

Change in spin-phonon coupling strength around 180 K.

Abstract

Temperature dependent X-ray diffraction and Raman spectroscopic studies were carried out on the flux grown single crystals of gallium ferrite with Ga:Fe ratio of 0.9:1.1. Site occupancy calculations from the Rietveld refinement of the X-ray data led to the estimated magnetic moment of ~0.60 \muB /f.u. which was in good agreement with the experimental data. Combination of these two measurements indicates that there is no structural phase transition in the material between 18 K to 700 K. A detailed line shape analysis of the Raman mode at ~375 cm^-1 revealed a discontinuity in the peak position data indicating the presence of spin-phonon coupling in gallium ferrite. A correlation of the peak frequency with the magnetization data led to two distinct regions across a temperature ~180 K with appreciable change in the spin-phonon coupling strength from ~ 0.9 cm^-1 (T < 180 K) to 0.12 cm-1 (180 K < T < Tc). This abrupt change in the coupling strength at ~180 K strongly suggests an altered spin dynamics across this temperature.