Effect of surface induced nucleation of ferroelastic domains on   polarization switching behavior 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 $90^{o}$ domain structures.   It is also found that no nucleation of $90^{o}$ domain structure takes place in a system with semi-infinite (corner free) geometry. For the corner free case, the polarization switches by $180^{o}$ 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. 
Rajeev Ahluwalia and Wenwu Cao