Nonlinear And Nonlocal Continuum Theory On Domain Walls In Ferroelectrics

The domain structures in ferroelectrics can be described by a Landau-Ginzburg type theory with the twin and twin band (domain) structures being nonlinear and nonlocal excitations of the ferroelectric phase. The polarization gradients in the theory reflect the degree of nonlocal coupling along different crystallographic orientations. These gradient parameters can be obtained either from the dispersion surface of the soft mode or through fitting the polarization profile measured by the holographic electron microscopy.