Phase field modeling of domain structures and P-E hysteresis in thin ferroelectric layers with deadlayers

The phase field method was used for the simulation of the domain structure evolution and polarization-applied field hysteresis in thin ferroelectric layers with deadlayers. The simulation demonstrated that the hysteresis loop shape depends on the thickness of the deadlayer and the strength of electrostatic interactions. The systems with a thin deadlayer and/or weaker electrostatic interactions produce a rectangular loop with a large remnant polarization value. The systems with a thicker deadlayer and/or stronger electrostatic interactions produce dumbbell-shaped double loops with an approximately zero remnant polarization. It is shown that the transformation from a poled single-domain state to a polydomain state can produce either the 180 degrees domain structure when elastic interactions in the layer are weak or the 90 degrees c/a structure when elastic interactions are strong. It is demonstrated that the type of the domain structure produced by the single-domain to polydomain transformation can affect the possibility of further changes in the domain structure in a varying applied field, and that 180 degrees domain structures produced by this transformation can have a columnar morphology instead of stripe domains.