Surface Effect on Domain Wall Width in Ferroelectrics

TL;DR

This paper investigates how surface effects, including depolarization fields, strain, and surface energy, influence the width and profile of domain walls in ferroelectric films, revealing complex dependencies and long-range behaviors.

Contribution

It provides a detailed analysis of surface and elastic effects on domain wall profiles using Landau-Ginzburg-Devonshire theory, highlighting new insights into surface-induced broadening and power-law decay.

Findings

Surface energy and elastic stress both cause domain wall broadening at the surface.

Domain wall profile exhibits a long-range power law decay near the surface.

Elastic stress effects dominate in high piezoelectric coupling materials with minimal surface energy.

Abstract

We study the effect of depolarization field related with inhomogeneous polarization distribution, strain and surface energy parameters on a domain wall profile near the surface of a ferroelectric film within the framework of Landau-Ginzburg-Devonshire phenomenology. Both inhomogeneous elastic stress and positive surface energy lead to the wall broadening at electrically screened surface. For ferroelectrics with weak piezoelectric coupling, the extrapolation length that defines surface energy parameter, affects the wall broadening more strongly than inhomogeneous elastic stress. Unexpectedly, the domain wall profile follows a long-range power law when approaching the surface, while it saturates exponentially in the bulk. In materials with high piezoelectric coupling and negligibly small surface energy (i.e. high extrapolation length) inhomogeneous elastic stress effect dominates.