Domains In Ferroelectric Films Research Articles

Boundary conditions control of topological polar nanodomains in epitaxial BiFeO3 (110) multilayered films

Topological structures in ferroelectric materials play a crucial role in the potential applications of high-density memories and are currently the subject of intensive interest. Interfaces with local symmetry breaking have garnered wide attention in designing the topological domains in ferroelectric films by regulating the different boundary conditions. Here, we present multiple topological polar nanodomains near the heterointerfaces in the trilayered systems of BiFeO3/GdScO3/BiFeO3 grown on [110]-oriented TbScO3 substrates. The formation and stabilization of these topological polar states depend on the electrical and mechanical boundary conditions of the BiFeO3 layers. Aberration-corrected transmission electron microscopy observation reveals that the topological polar nanodomains, including nano-scale vortices and flux-closures at the termination of 109° domain walls and the semi-vortices at the end of 180° domain walls, are stabilized in the BiFeO3 layers confined by two orthorhombic structures. Furthermore, the formation of flux-closures near the BiFeO3/GdScO3 interface is influenced by the domain structures in the adjacent BiFeO3 layers, which is preferred by the 180° domain patterns rather than the 109° domain patterns. This work provides further understanding into the influences of boundary conditions on topological polar configurations and would offer guidance for designing novel topological states that enable the development of high-density memory devices.

Diffuse X-ray scattering from 180° ferroelectric stripe domains: polarization-induced strain, period disorder and wall roughness

A key element in ferroic materials is the presence of walls separating domains with different orientations of the order parameter. It is demonstrated that 180° stripe domains in ferroelectric films give rise to very distinct features in their diffuse X-ray scattering (DXS) intensity distributions. A model is developed that allows the determination of not only the domain period but also the period disorder, the thickness and roughness of the domain walls, and the strain induced by the rotation of the polarization. As an example, the model is applied to ferroelectric/paraelectric superlattices. Temperature-dependent DXS measurements reveal that the polarization-induced strain decreases dramatically with increasing temperature and vanishes at the Curie temperature. The motion of ferroelectric domain walls appears to be a collective process that does not create any disorder in the domain period, whereas pinning by structural defects increases the wall roughness. This work will facilitatein situquantitative studies of ferroic domains and domain wall dynamics under the application of external stimuli, including electric fields and temperature.

Fractal Dimension and Size Scaling of Domains in Thin Films of MultiferroicBiFeO3

Domains in ferroelectric films are usually smooth, stripelike, very thin compared with magnetic ones, and satisfy the Landau-Lifshitz-Kittel scaling law (width proportional to square root of film thickness). However, the ferroelectric domains in very thin films of multiferroic BiFeO3 have irregular domain walls characterized by a roughness exponent 0.5-0.6 and in-plane fractal Hausdorff dimension H||=1.4+/-0.1, and the domain size scales with an exponent 0.59+/-0.08 rather than 1/2. The domains are significantly larger than those of other ferroelectrics of the same thickness, and closer in size to those of magnetic materials, which is consistent with a strong magnetoelectric coupling at the walls. A general model is proposed for ferroelectrics, ferroelastics or ferromagnetic domains which relates the fractal dimension of the walls to domain size scaling.