Origin of Stationary Domain Wall Enhanced Ferroelectric Susceptibility

TL;DR

This study reveals that stationary domain walls in ferroelectrics like PbTiO3 significantly enhance low-field dielectric susceptibility due to frustrated dipoles within the walls, independent of domain wall motion.

Contribution

It provides a theoretical and computational analysis of how stationary domain walls contribute to dielectric enhancement, highlighting the role of frustrated dipoles within the walls.

Findings

Dielectric permittivity increases with domain wall density.

Stationary domain walls contribute to dielectric susceptibility without lateral motion.

Frustrated dipoles within domain walls are key to permittivity enhancement.

Abstract

Ferroelectrics usually adopt a multi-domain state with domain walls separating domains with polarization axes oriented differently. It has long been recognized that domain walls can dramatically impact the properties of ferroelectric materials. The enhancement of low-field susceptibility/permittivity under subswitching conditions is usually attributed to the reversible domain wall vibration. Recent experiments highlight the stationary domain wall contribution to the dielectric susceptibility irrespective of any lateral displacements or deformations of the wall. We study the effects of domain walls on low-field permittivity of PbTiO$_3$ with density functional theory and molecular dynamics simulations. The static dielectric constant is calculated as a function of increasing domain wall density and temperature. We find an increase of dielectric permittivity with increasing domain wall density, which is expected to occur at low driving field where the lateral motion of domain walls is forbidden. Real-space decomposition of dielectric response reveals that frustrated dipoles within the finite width of the domain walls are responsible for the enhanced low-field permittivity.