The Study Of The Physical Properties Of Ferroelectric Multilayer Structure

In the framework of the transverse Ising Model (TIM), Landau phase transition theory and the electrostatic field theory, we study the physical properties of the ferroelectric thin film, bilayer, sandwich structure, multilayer with a non-polarization slab and a two-dimension polar lattice model with polar defects. The main work and results are as follows:First, the long-range interaction in ferroelectric material is sometimes neglected in the previous studies. We introduce the long-range interaction in the framework of the TIM and the Landau theory. A method beyond mean-field theory is applied to investigate the effects of the long-range interaction on the physical properties of the ferroelectric thin film. It is found that the enhancement of the long-range interaction will result in the increment of the phase transition temperature, the increase of the critical transverse field and the decrease of the critical size.Second, during the fabrication of the ferroelectric mutilayer, there must exist an interface between the different slab of the ferroelectric multilayer. In the framework of the long-range interaction, we study the interfacial effects on the pyroelectric and dielectric susceptibility of a ferroelectric bilayer for the first time. We find that the quantum effect can lead to the disappearance of some of the peaks of the pyroelectric and susceptibility of the bilayer. If the interfacial coupling of the ferroelectricbilayer is antiferroelectric, we find it is possible to exist triple hystersisloops once the parameters of the two slabs are selected appropriately. We give a detailed analysis on the occurrence and the disappearance of the triple hystersis. The quantum effect has an important role on the hysteresis, and can result in the disappearance of the triple hysteresis.Third, the ferroelectric bilayer with a thick interface may be taken as a ferroelectric sandwich structure, and the interface will play a nontrivial role on the pyroelectric properties of the ferroelectric multilayer. By extending the pyroelectric theory of a ferroelectric bilayer, we have presented the effective pyroelectric coefficient of a ferroelectric sandwich structure by use of the electrostatic theory. When the pyroelectric coefficient of the interface has a large deviation from that of the two-sided slabs and the dielectric constant of the interface is low, the effective pyroelectric coefficient of the sandwich structure may be one or two order higher than the largest pyroelectric coefficient of the components. This study can shed light on how to produce good pyroelectric devices.Fourth, impurity is often built in the ferroelectric material during the fabrication process. For the first time, we investigate the effects of the non-polarization layer on the polarization and the dielectric susceptibility of a ferroelectric multilayer. The increase of the thickness of the non-polarization slab will decrease the average polarization and the susceptibility of the multilayer. If the position of the non-polarization slabshifts from the center to the surface, the number of the peaks of the susceptibility will change, and a step-like polarization curve is found.Finally, two types of the dipolar defects are introduced into the lattice-based ferroelectric system. One type of the dipolar defects is that the position of the dipole displaces away from the lattice site, the other is the irreversible dipole. Applying the Monte-Carlo simulation on the system, we obtain the introducing of the dipolar defects will decrease the coercive field. The first type of the dipolar defects will cause two successive 90?rotations of the direction of the dipoles during the process of switching, while the switching behavior of the ferroelectric system with the second type of the dipolar defects shows almost a single 1800 flipping.