Bloch-type domain walls in rhombohedral BaTiO3

Abstract

Ferroelectric domain walls (FDWs) are usually considered to be of Ising type, but there have been suggestions in recent years that Bloch-type FDWs are also possible in some cases, e.g., in the rhombohedral phase of BaTiO3. The mechanically compatible and electrically neutral FDWs in rhombohedral BaTiO3 are of 71 • , 109 • , and 180 • type. We have investigated these FDWs based both on first-principles calculations and on a Ginzburg-Landau-Devonshire (GLD) model [P. Marton, I. Rychetsky, and J. Hlinka, Phys. Rev. B 81, 144125 (2010)]. The results from both approaches confirm the Ising nature of the 71 • FDW and the Bloch nature of the 180 • FDW, and predict both Ising-type and Bloch-type FDWs are possible for the 109 • case. Considering the relatively small rhombohedral strain in BaTiO3, the competition between the energies of Bloch and Ising FDWs can be discussed in terms of a picture in which a Bloch wall is regarded as being composed of a pair of smaller-angle Ising ones. A reduction by 40% in the parameters describing the gradient term in the GLD model brings it into better agreement with the first-principles results for detailed properties such as the energies and widths of the FDWs.

Polar nature of stress-induced twin walls in ferroelastic CaTiO3

“…In particular, recent theoretical works claim the possibility of Bloch-or Néel-type domain boundaries in addition to the traditional Ising type in the prototype ferroelectrics PbTiO 3 , LiNbO 3 , BaTiO 3 and PbZr 1-x Ti x O 3 . [35][36][37][38][39][40][41][42] Since the spatial resolution of our SHGM is much greater than the unit cell scale, it is difficult to quantitatively determine the boundary type only from the present experimental data. Nevertheless, from the viewpoint of the electrostatic energy, the Ising-type TWs are most preferable in ferroelastics because the adjacent domains are nonpolar.…”

Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles

“…First-principles theory has predicted the occurence of Bloch-like DW configurations in materials like LiNbO 3 [18] and BaTiO 3 in its rhombohedral phase [21].…”

“…In fact, we still lack a detailed structural and dynamical picture of the DWs, and in many cases we can only speculate about the structure-property relationships at work within them. Hence, there is a pressing need for predictive theoretical studies tackling the DWs at an atomistic level and at the relevant conditions of temperature, etc.The DW structure, and even the possible occurrence of DW-confined ferroic orders, have been discussed theoretically for decades, usually in the framework of continuum Ginzburg-Landau or phenomenological model theories [12][13][14][15][16][17][18][19][20][21][22]. Materials with competing structural instabilities have been a focus of attention, a good example being perovskite SrTiO 3 (STO).…”

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.…”

“…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.…”