Structure and energy of charged domain walls in ferroelectrics

The problem of the structure and energy of a charged 180-degree head-to-head domain wall is considered, using Landau theory. It was found that the scales controlling the wall structure can be very different from the Debye radius. Depending on the spontaneous polarization and the concentration of free carriers, these scales can be about the Thomas-Fermi screening length or about those typical for screening in nonlinear (Thomas-Fermi or Debye) regimes. In the typical case of perovskites, like BaTiO3, at room temperature, domain wall width is about the spatial scale of the nonlinear Thomas-Fermi screening.