Ising lines: Natural topological defects within ferroelectric Bloch walls

Abstract

Phase-field simulations demonstrate that the polarization order-parameter field in the Ginzburg-Landau-Devonshire model of rhombohedral ferroelectric ${\mathrm{BaTiO}}_{3}$ allows for an interesting linear defect, stable under simple periodic boundary conditions. This linear defect, here called the Ising line, can be described as an about 2-nm-thick intrinsic paraelectric nanorod acting as a highly mobile borderline between finite portions of Bloch-like domain walls of opposite helicity. These Ising lines play the role of domain boundaries associated with the Ising-to-Bloch domain-wall phase transition.