Abnormal dynamic behavior in a ferroelectric bilayer film

• Abnormal switching properties of a bilayer film are studied.
• Serious lag phenomenon of the hysteresis loop of the bilayer film occurs.
• There is a critical point for switching time and remanent polarization.
• The system exists a competed mechanism.

Based on the Landau–Khalatnikov equation of motion, the switching dynamic behavior (including switching time, hysteresis loop and remanent polarization) of a ferroelectric bilayer film with surface transition layer within each constituent thin film and an interfacial coupling between two thin films has been first studied. The results show that the serious lag phenomenon of the hysteresis loop of the bilayer film occurs due to the strong strength of the interfacial coupling. It is interesting to note that there is a critical point, which is an equilibrium point of two contrary actions of the surface transition layer and interfacial coupling. The abnormal behavior of the switching time and remanent polarization in the bilayer film is attributed to the competition of the surface transition layer and interfacial coupling.