Structural phase transitions and electronic phenomena at 180-degree domain walls in rhombohedral BaTiO₃

Анотація

The structure and electronic phenomena at the 180-degree domain wall in the rhombohedral phase of BaTiO₃ are described using Landau-Ginzburg-Devonshire theory. Dependent on the wall orientation, two types of domain wall behaviors are identified. The low-energy “achiral” phase occurs in the vicinity of the {110} orientation and has odd polarization profile invariant with respect to inversion about the wall center. The “chiral” phase occurs around {211} wall orientations and corresponds to mixed parity domain walls. The temperature-induced transformation between the phases is abrupt and is accompanied with 20%–30% change of the domain wall thickness. This process gives rise to the significant changes of the electronic structure of the wall. 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. The possible strategies for exploring these transitions based on direct measurements of domain wall width and conductive atomic force microscopy are discussed.