Long-range coupling interactions in ferroelectric sandwich structures

We study the ferroelectric system consisting of the sandwich structure (PbT iO3/BaTiO3/PbTiO3) by using the Ginzburg-Landau phenomenological theory, an d emphasize the importance of the long-range coupling interaction to the fe rroelectric behavior of the system. We find that after introducing the long -range coupling interaction to the ferroelectric behavior of the sandwich s ystem, the average spontaneous polarization of the interlayer (BaTiO3) incr eases and a size-driven phase transition disappears. The larger the range o f the long-range coupling, the larger the average spontaneous polarization. When the range of the long-range coupling is large enough, the average spo ntaneous polarization increases gradually with decreasing interlayer thickn ess, reaches one maximum at a certain finite thickness, and then decreases. The spatial distribution profile of the spontaneous polarization on the ra nge of the coupling interaction for different values of the interlayer thic kness is obtained, and the dependence of the averaged polarization on tempe rature is also examined. (C) 2001 American Institute of Physics.