Effect of surface induced nucleation of ferroelastic domains on polarization switching in constrained ferroelectrics

The role of the surface during polarization switching in constrained ferroelectrics is investigated using the time-dependent Ginzburg-Landau theory. The model incorporates the elastic and electrostrictive effects in the form of a long-range interaction that is obtained by eliminating the strain fields subject to the elastic compatibility constraint. A square-shaped finite sized constrained ferroelectric system with vanishing surface polarization is considered. Computer simulations of the hysteresis reveal that the corners of the constrained square act as nucleation sources for 90degrees domain structures. It is also found that no nucleation of the 90degrees domain structure takes place in a system with semi-infinite (corner free) geometry. For the corner free case, the polarization switches by 180degrees reorientations and a front of the reverse domains emerges from the surface, eventually sweeping over the entire system. Size dependence of the hysteresis loops is also studied. (C) 2003 American Institute of Physics.