Magentically-Induced Lattice Distortions and Ferroelectricity in Magnetoelectric GdMnO3

TL;DR

This study explores how magnetic fields induce lattice distortions and ferroelectricity in GdMnO3, revealing the ionic displacive nature of the phase transition and quantifying spontaneous polarization.

Contribution

It provides new insights into the magnetically induced ferroelectric phase transition mechanisms in GdMnO3 through Raman spectroscopy analysis.

Findings

Frequency change of Ag tilt mode aligns with Mn-Gd spin stabilization.

Estimated spontaneous polarization of 480 μC/m2 matches previous reports.

Large magnetic hysteresis indicates magnetrostiction at low temperatures.

Abstract

In this work we investigate the magnetic field dependence of Ag octahedra rotation (tilt) and B2g symmetric stretching modes frequency at different temperatures. Our field-dependent Raman investigation at 10K is interpreted by an ionic displacive nature of the magnetically induced ferroelectric phase transition. The frequency change of the Ag tilt is in agreement with the stabilization of the Mn-Gd spin arrangement, yielding the necessary conditions for the onset of ferroelectricity on the basis of the inverse Dzyaloshinskii-Moriya interaction. The role of the Jahn-Teller cooperative interaction is also evidenced by the change of the B2g mode frequency at the ferroelectric phase transition. This frequency change allows estimating the shift of the oxygen position at the ferroelectric phase transition and the corresponding spontaneous polarization of 480 {\mu}C/m2, which agrees with earlier reported values in single crystals. Our study also confirms the existence of a large magnetic hysteresis at the lowest temperatures, which is a manifestation of magnetrostiction.