Improper flexoelectricity in hexagonal rare-earth ferrites
Abstract
Flexoelectricity is a universal effect that generates electric polarization due to broken inversion symmetry caused by local strain gradient. The large strain gradient at nanoscale makes flexo-electric effects, especially in nanoscopic ferroelectric materials, promising in sensors, actuator, energy harvesting, and memory applications. In this work, we studied flexoelectricity in hexagonal ferrites h-YbFeO3, an improper ferroelectric expected to have weak piezoelectricity and low sensitivity to depolarization field, which are advantageous for studying flexoelectric effects. We show that in h-YbFeO3 epitaxial thin films, strain gradient on the order of 10^6 m-1 occurs near grain boundaries and edge dislocation, which has a significant impact on the non-polar K3 structural distortion that induces spontaneous polarization. The phenomenological model based on the Landau theory of improper ferroelectricity suggests an indirect flexoelectric effect on the order of 10 nC/m in h-YbFeO3, which is substantially larger than the expectation from Kogan mechanism. These results reveal a novel microscopic mechanism of coupling between strain gradient and polarization mediated by structural distortion, which we call improper flexoelectricity.
Cite
@article{arxiv.2409.17022,
title = {Improper flexoelectricity in hexagonal rare-earth ferrites},
author = {Xin Li and Guodong Ren and Yu Yun and Arashdeep Singh Thind and Amit Kumar Shah and Abbey Bowers and Rohan Mishra and Xiaoshan Xu},
journal= {arXiv preprint arXiv:2409.17022},
year = {2025}
}