Chiral phase transition at 180° domain walls in ferroelectric PbTiO_3 driven by epitaxial compressive strains

摘要

Chiral ferroelectric domain walls are theoretically predicted to be promising in novel electronic memory devices. In order to develop a chirality-based device, understanding the chiral phase transition is of great importance for chirality manipulation. In this work, we systematically studied the chiral phase transition at 180° domain walls in ferroelectric PbTiO_3 (PTO) under epitaxial compressive strains by first principles calculations. It is found that with the increase of the compressive strain, the Bloch components decrease due to the coupling of polarization and strain, while the components normal to domain walls increase because of the large stress gradients. The domain wall changes from a mixed Ising-Bloch type to the Ising type. It is also found that the domain wall energy increases with the increment of compressive strain, indicating that the spacings of 180° domain walls would be large for the highly compressed PTO films. These findings may provide useful information for the development of novel ferroelectric devices.