Abstract
A Landau-Devonshire theory with Landau-Khalatnikov dynamic equation is used to investigate the polarization reversal of first-order ferroelectric thin films. Spatial variation of the order parameter P is considered near the surfaces of ferroelectric film, where the surfaces are characterized by an extrapolation length delta. The two surfaces of ferroelectric film have been assumed to be identical, and symmetric boundary conditions are introduced. To simulate switching properties by an applied step field, Euler-Lagrange equation is solved numerically. The hysteresis loops, time evolution of average polarization and switching current are plotted for a few temperature intervals. The appearance of double hysteresis loops for temperature above the superheating temperature t(SH) suggests that the first-order ferroelectrics can behave like antiferroelectrics. It is discovered that in two temperature intervals (t(SC) < t < t(C) and t(C) < t < t(SH)) double-peaked switching curve appears, which implies that switching take place in two stages; and it may be due to the coexistence of paraelectric and ferroelectric phase within these temperature intervals.