Eugene A. Eliseev, Peter V. Yudin, Sergei V. Kalinin, Nava Setter, Alexander K. Tagantsev, Anna N. Morozovska
Using Landau-Ginzburg-Devonshire theory we self-consistently calculate the influence of the flexoelectric coupling and orientation on the 180-degree domain wall structure, intrinsic energy and static conductivity in rhombohedral phase of n-type BaTiO3. Two types of domain wall structures (phases of the wall) exist depending on the wall orientation. The stable "odd" phase occurs in the vicinity of the {110} wall orientation and has polarization profile invariant with respect to inversion about the wall center. The second "bistable" phase occurs around {211} wall orientations and corresponds to mixed parity chiral domain walls that may be switched from the left-handed state to the right-handed one. The transformation between the phases is abrupt and close to the first order. The flexoelectric effect reduces the symmetry of the wall energy angular anisotropy and strongly influences the value and rotation symmetry of the polarization component normal to the wall plane. The component, inherent to the both wall types, causes the depolarization field and electric potential variation across the wall. Electric potential variation leads to free carriers accumulation by the wall. Depending on the temperature and flexoelectric coupling strength the wall static conductivity becomes at least one order higher than in the single-domain region, creating the conductivity enhancement pronounced and easily detectable by current-AFM.
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http://arxiv.org/abs/1208.3243
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