Ferroelectric phase transitions and dynamical behavior in KNbO3/KTaO3 superlattices by molecular-dynamics simulation

The phase transitions and dynamical behavior of superlattices consisting of equal-thickness layers of a perovskite ferroelectric (KNbO3) and a perovskite paraelectric (KTaO3) are explored using molecular-dynamics simulation. We find that the response in the plane and in the modulation direction are essentially decoupled. The Curie temperature for the transition from a polarized to unpolarized state in the modulation direction decreases approximately linearly with modulation length, Λ, for Λ>12; for smaller modulation lengths, it is essentially constant. The Curie temperature in the plane appears to be only weakly modulation-length dependent. We relate our results to experimental findings on the same system.