Origin of magnetoelectric behavior in BiFeO$_3$

TL;DR

This study uses density functional calculations to elucidate the origin of magnetoelectric behavior in BiFeO$_3$, accurately predicting its properties, phase transitions, and ferroelectric polarization, aligning well with experimental data.

Contribution

The paper provides a detailed theoretical analysis of BiFeO$_3$'s properties, including structural, electronic, and magnetic aspects, without requiring strong correlation effects, and explains the origin of its ferroelectricity.

Findings

BiFeO$_3$ is an insulator in A- and G-type antiferromagnetic phases.

A pressure-induced structural transition is predicted.

Large ferroelectric polarization mainly originates from Bi atoms.

Abstract

The magnetoelectric behavior of BiFeO$_3$ has been explored on the basis of accurate density functional calculations. The structural, electronic, magnetic, and ferroelectric properties of BiFeO$_3$ are predicted correctly without including strong correlation effect in the calculation. Moreover, the experimentally-observed elongation of cubic perovskite-like lattice along the [111] direction is correctly reproduced. At high pressure we predicted a pressure-induced structural transition and the total energy calculations at expanded lattice show two lower energy ferroelectric phases, closer in energy to the ground state phase. Band-structure calculations show that BiFeO$_3$ will be an insulator in A- and G-type antiferromagnetic phases and a metal in other magnetic configurations. Chemical bonding in BiFeO$_3$ has been analyzed using various tools and electron localization function analysis shows that stereochemically active lone-pair electrons at the Bi sites are responsible for displacements of the Bi atoms from the centro-symmetric to the noncentrosymmetric structure and hence the ferroelectricity. A large ferroelectric polarization (88.7 $\mu$C/cm$^{2}$) is predicted in accordance with recent experimental findings. The net polarization is found to mainly ($>$ 98%) originate from Bi atoms. Moreover the large scatter in experimentally reported polarization values is due to the large anisotropy in the spontaneous polarization.