Magnetic-Field and External-Pressure Control of Ferroelectricity in Multiferroic Manganites

TL;DR

This study explores how magnetic fields and pressure influence ferroelectricity in GdMnO₃ crystals, revealing pressure reduces transition temperature and magnetic fields can suppress or enhance polarization.

Contribution

It demonstrates control of ferroelectricity in multiferroic manganites through magnetic fields and pressure, highlighting the first-order displacement nature of the transition.

Findings

Ferroelectric phase appears below 13K in GdMnO₃.

Small spontaneous polarization along the a axis can be reversed by electric field.

Pressure decreases the ferroelectric transition temperature.

Abstract

We have investigated dielectric properties in a series of crystals of $R$MnO$_{3}$ ($R$ is a rare earth ion) under magnetic fields and quasihydrostatic pressure. We have found that ferroelectric phase appeared in GdMnO$_3$ crystal below 13K. We have confirmed that a small spontaneous polarization exists along a axis ($P_a$) in the orthorhombic $Pbnm$ setting and that $P_a$ can be reversed by the dc electric field. The dielectric anomaly due to the ferroelectric transition accompanied thermal hysteresis and lattice striction. The ferroelectric transition temperature decreased with quasihydrostatic pressure. These results indicate that the ferroelectric transition is improper and is of the first-order displacement-type one. $P_a$ was easily collapsed by application of magnetic field of 0.4T parallel to the spin-canting direction ($H \| c$) while it was enhanced parallel to the easy axis ($H \| b$).