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 interracial 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 ofa ferroelectric bilayer film under two conditions of interracial coupling:ferroelectric and antiferroelectric coupling.The results show some unexpected phenomena for a small thickness of a ferroelectric bilayer film.