Polarization Pinning at Antiphase Boundaries in Multiferroic YbFeO$_3$

TL;DR

This study investigates how antiphase boundaries in YbFeO$_3$ thin films act as pinning sites for polarization, affecting ferroelectric switching, through atomic-scale imaging and theoretical calculations.

Contribution

It provides the first atomic-resolution characterization of antiphase boundaries in YbFeO$_3$ and links their structure to polarization pinning effects.

Findings

Antiphase boundaries contain a bridging FeO$_6$ octahedral layer.

Polarization reverses across the boundary due to structural changes.

APBs serve as domain-wall pinning sites, hindering switching.

Abstract

The switching characteristics of ferroelectrics and multiferroics are influenced by the interaction of topological defects with domain-walls. We report on the pinning of polarization due to antiphase boundaries in thin films of the multiferroic hexagonal YbFeO$_3$. We have directly resolved the atomic structure of a sharp antiphase boundary (APB) in YbFeO$_3$ thin films using a combination of aberration-corrected scanning transmission electron microscopy (STEM) and total energy calculations based on density-functional theory (DFT). We find the presence of a layer of FeO$_6$ octahedra at the APB that bridge the adjacent domains. STEM imaging shows a reversal in the direction of polarization on moving across the APB, which DFT calculations confirm is structural in nature as the polarization reversal reduces the distortion of the FeO$_6$ octahedral layer at the APB. Such APBs in hexagonal perovskites are expected to serve as domain-wall pinning sites and hinder ferroelectric switching of the domains.