First-principles study of spontaneous polarization in multiferroic BiFeO$_3$

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, and ferroelectric properties of BiFeO$_3$, predicting a large polarization consistent with recent experiments and providing insights into discrepancies with earlier measurements.

Contribution

It provides a detailed first-principles analysis of BiFeO$_3$, predicting a large ferroelectric polarization and explaining experimental discrepancies through modern polarization theory.

Findings

Predicted ferroelectric polarization of 90-100 μC/cm$^2$

Crystal structure is rhombohedral $R3c$

Electronic structure is insulating and antiferromagnetic

Abstract

The ground-state structural and electronic properties of ferroelectric BiFeO$_3$ are calculated using density functional theory within the local spin-density approximation and the LSDA+U method. The crystal structure is computed to be rhombohedral with space group $R3c$, and the electronic structure is found to be insulating and antiferromagnetic, both in excellent agreement with available experiments. A large ferroelectric polarization of 90-100 $\mu$C/cm$^2$ is predicted, consistent with the large atomic displacements in the ferroelectric phase and with recent experimental reports, but differing by an order of magnitude from early experiments. One possible explanation is that the latter may have suffered from large leakage currents. However both past and contemporary measurements are shown to be consistent with the modern theory of polarization, suggesting that the range of reported polarizations may instead correspond to distinct switching paths in structural space. Modern measurements on well-characterized bulk samples are required to confirm this interpretation.