The Study On The Physical Properties Of The Ferroelectric Thin Film

Within the framework of the TIM (transverse field model), using the EFT (effective field theory) and the MFT (mean field theory), considering the long-range effects and the interfacial effect, we studied the transition properties of the ferroelectric thin film, pyroelectric coefficient and dielectric susceptibility and triple hysteresis loop of the ferroelectric bilayer structure theoretically.The Curie temperature of ferroelectric films is studied using spin- 1/2 transverse Ising model with long-range interactions within the framework of an effective-field theory. The dependence of the Curie temperature on the thickness of the film, the surface interaction and the transverse field are investigated. The dependence of the Curie temperature and the critical transverse field on the long-range exponent is obtained.Long-range effects on the pyroelectric coefficient and susceptibility of a ferroelectric bilayer with a ferroelectric interfacial coupling are investigated by use of the transverse Ising model within the framework of mean field theory. The effects of the interfacial coupling and the transverse field on the pyroelectric coefficient and susceptibility of the bilayer are investigated by taking into account the long-range interaction. It is found that the pyroelectric coefficient and susceptibility increase with the decrease of the magnitude of the long-range interaction and the interfacial coupling when the temperature is lower than the phase transition temperature.We also find that the strong long-range interaction, the large transverse field and weak interfacial coupling can lead to the disappearance of some of the peaks of the pyroelectric coefficient and susceptibility of the ferroelectric bilayer. We believe that it is the reason why these phenomena always take place in the experimental studies.The intrinsic hysteresis of a ferroelectric bilayer with an antiferroelectric interfacial coupling is studied within the framework of TIM. We find it is possible to exist triplehysteresis loops once the parameters of the two slabs are selected appropriately. The effects of the thickness, the interfacial coupling constant and the temperature on the hysteresis of the bilayer are investigated. The quantum effect on the hysteresis is also examined; it is found that the quantum effect can result in the disappearance of the multi-state hysteresis.