The size and strain effects on the electric-field-induced domain evolution and hysteresis loop in ferroelectric BaTiO₃ nanofilms

The electric-field-induced evolution of stripe domains in BaTiO₃ nano-thin films is studied using molecular dynamics simulation method based on a shell model. The evolution of the 180° period stripe domains under a changing electric-field perpendicular to the film surface is investigated. It is found that both the thickness and the in-plane strain can influence the polarization distribution pattern and the domain switching process, and therefore affect the shape of hysteresis loop, which may be used to explain the discrepancy among existing experimental studies on the correlation between the thickness and the coercive field. Moreover, this simulation on the atomic-level domain evolution provides the microscopic insight of the domain switching, which can help us better understand the behaviors and properties of the ferroelectric thin films.