Effect of epitaxial strain on ferroelectric polarization in multiferroic BiFeO3 films

TL;DR

This study investigates how epitaxial strain affects the structural evolution and ferroelectric polarization in BiFeO3 films, revealing that polarization remains stable despite significant structural changes due to strain relaxation.

Contribution

It demonstrates that ferroelectric polarization in BiFeO3 films is resilient to structural evolution caused by epitaxial strain relaxation.

Findings

Structural transition from tetragonal to rhombohedral with increasing thickness

Ferroelectric polarization remains nearly unchanged despite structural evolution

Strain relaxation does not significantly affect polarization in BiFeO3 films

Abstract

Multiferroic BiFeO3 epitaxial films with thickness ranging from 40 nm to 960 nm were grown by pulsed laser deposition on SrTiO3 (001) substrates with SrRuO3 bottom electrodes. X-ray characterization shows that the structure evolves from angularly-distorted tetragonal with c/a ~ 1.04 to more bulk-like distorted rhombohedral (c/a ~ 1.01) as the strain relaxes with increasing thickness. Despite this significant structural evolution, the ferroelectric polarization along the body diagonal of the distorted pseudo-cubic unit cells, as calculated from measurements along the normal direction, barely changes.