Ideal barriers to polarization reversal and domain-wall motion in strained ferroelectric thin films

TL;DR

This study uses first-principles calculations to explore how epitaxial strain affects domain-wall motion and polarization in strained ferroelectric thin films like PTO, PZO, and PZT, revealing material-specific responses and structural sensitivities.

Contribution

It provides a detailed computational analysis of intrinsic barriers and strain effects on domain switching in ferroelectric thin films, highlighting differences among PTO, PZO, and PZT.

Findings

PTO has larger polarization but lower energy barrier to domain reversal than PZO.

Epitaxial strain significantly affects polarization and domain-wall energy, especially in PTO.

Ferroelectric properties in PZT phases deviate from Vegard's law and can be approximated by averaging over unit cells.

Abstract

The ideal intrinsic barriers to domain switching in c-phase PbTiO_3 (PTO), PbZrO_3 (PZO), and PbZr_{1-x}Ti_xO_3 (PZT) are investigated via first-principles computational methods. The effects of epitaxial strain on the atomic structure, ferroelectric response, barrier to coherent domain reversal, domain-wall energy, and barrier to domain-wall translation are studied. It is found that PTO has a larger polarization, but smaller energy barrier to domain reversal, than PZO. Consequentially the idealized coercive field is over two times smaller in PTO than PZO. The Ti--O bond length is more sensitive to strain than the other bonds in the crystals. This results in the polarization and domain-wall energy in PTO having greater sensitivity to strain than in PZO. Two ordered phases of PZT are considered, the rock-salt structure and a (100) PTO/PZO superlattice. In these simple structures we find that the ferroelectric properties do not obey Vergard's law, but instead can be approximated as an average over individual 5-atom unit cells.