Influence of strain and oxygen vacancies on the magnetoelectric properties of multiferroic bismuth ferrite

TL;DR

This study uses first principles calculations to explore how strain and oxygen vacancies influence the ferroelectric and magnetic properties of multiferroic bismuth ferrite, revealing their relative insensitivity to strain and oxygen vacancies.

Contribution

It provides novel insights into the effects of strain and oxygen vacancies on BiFeO_3's properties, contrasting with conventional ferroelectrics and aligning with recent experimental findings.

Findings

Electric polarization is largely unaffected by strain or oxygen vacancies.

Oxygen vacancies can slightly alter magnetization and create Fe^{2+}.

Magnetization remains unaffected by strain.

Abstract

The dependencies on strain and oxygen vacancies of the ferroelectric polarization and the weak ferromagnetic magnetization in the multiferroic material bismuth ferrite, BiFeO_3, are investigated using first principles density functional theory calculations. The electric polarization is found to be rather independent of strain, in striking contrast to most conventional perovskite ferroelectrics. It is also not significantly affected by oxygen vacancies, or by the combined presence of strain and oxygen vacancies. The magnetization is also unaffected by strain, however the incorporation of oxygen vacancies can alter the magnetization slightly, and also leads to the formation of Fe^{2+}. These results are discussed in light of recent experiments on epitaxial films of BiFeO_3 which reported a strong thickness dependence of both magnetization and polarization.