Ab-initio study of competing magnetic configurations in cubic BiFeO3 alloys

Using ab-initio calculations, we study the properties of the multiferroic BiFeO3 compounds in the perfect cubic perovskite lattice structure. We show that the appearance of magnetism is energetically favorable. Except the ferromagnetic structure, there are three possible antiferromagnetic arrangements, which are close in energy, and for large values of the lattice constant a G-type antiferromagnetism is the most stable magnetic order. Fe atoms are responsible for the spin magnetic moments while the values of the induced spin moments at the other sites depend strongly on the local environment of the atoms. There is a significant charge transfer from the Fe and Bi atoms towards the p-states of O atoms.

► Ab-initio calculations are employed to study BiFeO3 in its cubic phase.
► Fe atoms carry mainly the spin magnetic moments.
► Fe spin moments depend only on the lattice constant and not their relative orientation.
► For small lattice constants the ferromagnetic ordering of Fe moments is favoured.
► For larger lattice constants a G-type antiferromagnetism is the ground-state.