Size Effects of the Properties in a Ferroelectric Bilayer Film with Surface Transition Layers

Using the transverse Ising model theory, a ferroelectric bilayer film, considering the surface transition layer within each constituent slab and an interfacial coupling between two slabs, is investigated in the framework of the mean-field approximation. We discuss in detail the thickness effects of the spontaneous polarization and dielectric susceptibility of a ferroelectric bilayer film under two conditions of interfacial coupling: ferroelectric and antiferroelectric coupling. The results show some unexpected phenomena for a small thickness of a ferroelectric bilayer film.