Strain-induced isosymmetric phase transition in BiFeO3

TL;DR

This study uses first-principles calculations to show that applying significant compressive strain to BiFeO3 induces an isosymmetric phase transition with notable structural and magnetic changes, including polarization rotation and increased magnitude.

Contribution

It predicts a strain-induced isosymmetric phase transition in BiFeO3 with detailed structural, polarization, and magnetic property changes, expanding understanding of strain effects in multiferroics.

Findings

Compressive strain >4% causes a phase transition in BiFeO3.

Polarization rotates from [111] to nearly [001] with increased magnitude.

Magnetic ordering temperature is suppressed at high strain.

Abstract

We calculate the effect of epitaxial strain on the structure and properties of multiferroic bismuth ferrite, BiFeO3, using first-principles density functional theory. We find that, while small strains cause only quantitative changes in behavior from the bulk material, compressive strains of greater than 4% induce an isosymmetric phase transition accompanied by a dramatic change in structure. In striking contrast to the bulk rhombohedral perovskite, the highly strained structure has a c/a ratio of ~1.3 and five-coordinated Fe atoms. We predict a rotation of polarization from [111] (bulk) to nearly [001], accompanied by an increase in magnitude of ~50%, and a suppression of the magnetic ordering temperature. Intriguingly, our calculations indicate critical strain values at which the two phases might be expected to coexist.