Ferroelectric polarization switching with a remarkably high activation-energy in orthorhombic GaFeO3 thin films

TL;DR

This study demonstrates large ferroelectric polarization in orthorhombic GaFeO3 thin films with a remarkably high activation energy for switching, indicating exceptional stability and potential for high-temperature applications.

Contribution

The paper reports the first demonstration of large ferroelectric polarization in o-GFO thin films with an exceptionally high activation energy for polarization switching.

Findings

Net polarization of ~35 μC/cm2 on STO substrate

High coercive field of ±1400 kV/cm at room temperature

Activation energy for switching is 1.05 eV per formula unit

Abstract

Orthorhombic GaFeO3 (o-GFO) with the polar Pna21 space group is a prominent ferrite by virtue of its piezoelectricity and ferrimagnetism, coupled with magneto-electric effects. Herein, we unequivocally demonstrate a large ferroelectric remanent polarization in undoped o-GFO thin films by adopting either a hexagonal strontium titanate (STO) or a cubic yttrium-stabilized zirconia (YSZ) substrate. The polarization-electric-field hysteresis curves of the polar c-axis-grown o-GFO film on a SrTiO3/STO substrate show the net switching polarization of ~35 {\mu}C/cm2 with an unusually high coercive field of +-1400 kV/cm at room temperature. The PUND measurement also demonstrates the switching polarization of ~26 {\mu}C/cm2. The activation energy for the polarization switching, as obtained by density-functional theory calculations, is remarkably high, 1.05 eV per formula unit. This high value accounts for the observed stability of the polar Pna21 phase over a wide range of temperature up to 1368 K.