The Study On The Pyroelectric Properties Of The Ferroelectric Superlattice

In this paper the pyroelectric properties of the ferroelectric superlartice consisting of two different ferroelectric materials are investigated based on the transverse Ising model (TIM). We consider the long-range interaction, the phonon-pseudospin interaction, the interfacial effects and the size effect respectively.Firstly, within the framework of spin- 1/2 transverse Ising model (TIM), the long-range effects on the pyroelectric properties of a ferroelectric superlartice are studied by use of the beyond mean-field theory. The effects of the interfacial coupling and the thickness of one period on the pyroelectric properties of the superlartice are investigated by taking into account the long-range interaction.We find that I ) with the increase of the long-range interaction, the interfacial coupling and the thickness of one period, the phase transition temperature of the ferroelectric superlartice increases. II) with the increase of the long-range interaction and the interfacial coupling, the pyroelectric coefficient before the phase transition temperature decreases. III) the increase of the long-range interaction results in the decrease of the number of the pyroelectric peaks in the temperature curve of pyroelectric coefficient. IV) for the strong interfacial coupling, there exist three pyroelectric peaks in the temperature curve of pyroelectric coefficient, and with the decrease of the interfacial coupling, the number of the pyroelectric peaks will decrease gradually. V) with the decrease of the thickness of one period, the two pyroelectric peaks become one gradually.Secondly, within the framework of the transverse Ising model, we investigate the effects of the phonon-pseudospin interaction on the pyroelectric properties of a ferroelectric superlattice by use of the Green Function (GF). The effects of the size effect on pyroelectric properties of the superlattice are investigated by taking into account the phonon-pseudospin interaction.We obtain that I ) with the increase of the phonon-pseudospin interaction and the thickness of the superlattice, the phase transition temperature of the superlattice will increase. II ) the increase of the phonon-pseudospin interaction leads to the change of the number of the pyroelectric peaks in the temperature curve of pyroelectric coefficient and to the change of the pyroelectric coefficient. III) with the increase of the thickness of the superlattice, the pyroelectric peaks will change. These results indicate that the phonon-pseudospin interaction should be taken into account for the physics properties in ferroelectric materials.