Landau-Ginzburg-Devonshire theory of the chiral phase transition in ${180}^{\ensuremath{\circ}}$ domain walls of ${\mathrm{PbTiO}}_{3}$

Landau-Ginzburg-Devonshire theory of the chiral phase transition in $180^{\circ}$ domain walls of ${PbTiO}_{3}$

I. Rychetsky, W. Schranz, and A. Tröster

Phys. Rev. B 108, 104107 – Published 21 September 2023

Abstract

A new mechanism leading to a switchable Bloch-type polarization in a domain wall separating two ferroelectric domain states is proposed. A biquadratic coupling of the primary order parameter and its gradient originating from inhomogeneous electrostriction triggers the chiral phase transition (Ising-to-Bloch) in the domain walls (DW) with softening of the local polar mode and anomalous increase of the dielectric susceptibility at the phase transition temperature $T_{D W} < T_{c}$ . This mechanism describes the origin and properties of the polar Bloch component, which appears below $T_{D W}$ additionally to the antipolar Néel component in the $180^{\circ}$ DW of ${PbTiO}_{3}$ . The tensile strain of the DW plane promotes the development of the Bloch polarization.