Domain walls of ferroelectricBaTiO3within the Ginzburg-Landau-Devonshire phenomenological model

Abstract

Mechanically compatible and electrically neutral domain walls in tetragonal, orthorhombic and rhombohedral ferroelectric phases of BaTiO3 are systematically investigated in the framework of the phenomenological Ginzburg-Landau-Devonshire (GLD) model with parameters of Ref. [Hlinka and Marton, Phys. Rev. 74, 104104 (2006)]. Polarization and strain profiles within domain walls are calculated numerically and within an approximation leading to the quasi-one-dimensional analytic solutions applied previously to the ferroelectric walls of the tetragonal phase [W. Cao and L.E. Cross, Phys. Rev. 44, 5 (1991)]. Domain wall thicknesses and energy densities are estimated for all mechanically compatible and electrically neutral domain wall species in the entire temperature range of ferroelectric phases. The model suggests that the lowest energy walls in the orthorhombic phase of BaTiO3 are the 90-degree and 60-degree walls. In the rhombohedral phase, the lowest energy walls are the 71-degree and 109-degree walls. All these ferroelastic walls have thickness below 1 nm except for the 90-degree wall in the tetragonal phase and the 60-degree S-wall in the orthorhombic phase, for which the larger thickness of the order of 5 nm was found. The antiparallel walls of the rhombohedral phase have the largest energy and thus they are unlikely to occur. The calculation indicates that the lowest energy structure of the 109-degree wall and few other domain walls in the orthorhombic and rhombohedral phases resemble Bloch-like walls known from magnetism.

Bistability of ferroelectric domain walls: Morphotropic boundary and strain effects

“…[5][6][7][8] The results from Ref. 8 suggest that the approximation neglecting flexoelectricity, which is used in the present paper, provides an acceptable accuracy for the description of the structure of the walls.…”

“…8 suggest that the approximation neglecting flexoelectricity, which is used in the present paper, provides an acceptable accuracy for the description of the structure of the walls. The publications [5][6][7][8] identify that in addition to the Ising and Bloch structures, the wall can exhibit a more complicated, so-called bichiral structure. Being mainly interested in the first two structures, below in Secs.…”

“…The stability of the Ising walls depends on the gradient term anisotropy parameter , which is unknown for PZT. For typical perovskites this parameter may be different: for pure PbTiO 3 the ≈ 1.7, 21 for BaTiO 3 ≈ 0.075, 5 and for KaTaO 3 ≈ 0.7. 22 To cover different possible situations we vary this parameter.…”

“…[2][3][4] The intention to create nanodevices on the basis of domain walls motivates further fundamental research of their internal structures. Of special interest are theoretical results predicting bistable domain walls 5,6 where information may be potentially stored. This type of wall may exist between two oppositely poled domains (180…”

“…This feature makes Bloch walls interesting objects from the point of view of dense memory applications. To the best of our knowledge the only material where Bloch walls are predicted is the rhombohedral phase of BaTiO 3 , [5][6][7][8] and this is done by numerical simulations, based on LandauGinsburg-Devonshire (LGD) theory and ab initio calculations. However, such domain walls may have limited applications because of difficulties, associated with cryogenic temperatures needed to obtain this phase in the material.…”