Depolarizing field and “real” hysteresis loops in nanometer-scale ferroelectric films

Abstract

The authors give detailed analysis of the effect of depolarizing field in nanometer-size ferroelectric capacitors studied by Kim et al. [Phys. Rev. Lett.95, 237602 (Year: 2005)]. They calculate a critical thickness of the homogeneous state and its stability with respect to domain formation for strained thin films of Ba Ti O 3 on Sr Ru O 3 ∕ Sr Ti O 3 substrate within the Landau theory. While the former ( 2.5 nm ) is the same as given by ab initio calculations, the actual critical thickness is set by the domains at 0.8 nm . There is a large Merz’s activation field for polarization relaxation. Remarkably, the results show a negative slope of the “actual” hysteresis loops, a hallmark of the domain structures in ideal thin films with imperfect screening.