We investigate the energetics of the intrinsic defects in bulk multiferroic BiFeO${}_3$ and explore their implication for magnetization using a first-principles approach based on density functional theory. We find that the dominant defects in oxidizing (oxygen-rich) conditions are Bi and Fe vacancies and in reducing (oxygen-poor) conditions are O and Bi vacancies. The calculated carrier concentration shows that the BiFeO${}_3$ grown in oxidizing conditions has p-type conductivity. The conductivity decreases with oxygen partial pressure, and the material becomes insulating with a tendency for n-type conductivity. We find that the Bi and Fe vacancies produce a magnetic moment of $\sim$1${\mu }_{\mathrm{B}}$ and 5${\mu }_{\mathrm{B}}$ per vacancy, respectively, for p-type BiFeO${}_3$ and none for insulating BiFeO${}_3$. O vacancies do not introduce any moment for both p-type and insulating BiFeO${}_3$. Calculated magnetic moments due to intrinsic defects are consistent with those reported experimentally for bulk BiFeO${}_3$.

• Received 30 November 2011

DOI:https://doi.org/10.1103/PhysRevB.85.104409