Correlation Between Structure And C-Afm Contrast Of 180-Degree Domain Walls In Rhombohedral Bati03

TL;DR

This study uses Landau-Ginzburg-Devonshire theory to analyze 180-degree domain walls in rhombohedral BaTiO3, revealing phase-dependent structures, abrupt phase transitions, and their correlation with conductivity and c-AFM contrast.

Contribution

It identifies two distinct domain wall phases, describes their abrupt transition, and links structural changes to conductivity variations detectable by c-AFM.

Findings

Two domain wall phases with different structures exist depending on orientation.

Phase transition involves 20-30% change in domain wall thickness.

Conductivity at domain walls can be an order of magnitude higher, enhancing c-AFM contrast.

Abstract

Using Landau-Ginzburg-Devonshire theory we describe 180-degree domain wall structure, intrinsic energy and carrier accumulation in rhombohedral phase of BaTiO3 as a function of the wall orientation and flexoelectric coupling strength. Two types of domain wall structures (phases of the wall) exist depending on the wall orientation. The low-energy 'achiral' phase occurs in the vicinity of the {110} wall orientation and has odd polarization profile invariant with respect to inversion about the wall center. The second 'chiral' phase occurs around {211} wall orientations and corresponds to mixed parity domain walls that may be of left-handed or right-handed chirality. The transformation between the phases is abrupt, accompanied with 20-30% change of the domain wall thickness and can happen at fixed wall orientation with temperature change. We suggest that the phase transition may be detected through domain wall thickness change or by c-AFM. The structure of the domain wall is correlated to its conductivity through polarization component normal to the domain wall, which causes free carriers accumulation. Depending on the temperature and flexoelectric coupling strength relative conductivity of the wall becomes at least one order of magnitude higher than in the single-domain region, creating c-AFM contrast enhancement pronounced and detectable.