Landau-Ginzburg-Devonshire theory of the chiral phase transition in 180° domain walls of PbTiO3

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-DW < T-c. This mechanism describes the origin and properties of the polar Bloch component, which appears below T-DW additionally to the antipolar Neel component in the 180(degrees) DW of PbTiO3. The tensile strain of the DW plane promotes the development of the Bloch polarization.

Automated summary

This study proposes a new mechanism that leads to a switchable Bloch-type polarization in a domain wall separating two ferroelectric domain states. The mechanism is triggered by the biquadratic coupling of the primary order parameter and its gradient originating from inhomogeneous electrostriction. The study also describes the origin and properties of the polar Bloch component.