First-principles prediction of coexistence of magnetism and ferroelectricity in rhombohedral Bi2FeTiO6

First principles calculations based on the density functional theory within the local spin density approximation plus U(LSDA + U) scheme, show rhombohedral Bi2FeTiO6 is a potential multiferroic in which the magnetism and ferroelectricity coexist. A ferromagnetic configuration with magnetic moment of 4μB4μB per formula unit has been reported with respect to the minimum total energy. Spontaneous polarization of 27.3 μC/cm227.3 μC/cm2, caused mainly by the ferroelectric distortions of Ti, was evaluated using the berry phase approach in the modern theory of polarization. The Bi-6s stereochemical activity of long-pair and the ‘d0-ness’ criterion in off-centring of Ti were coexisting in the predicted new system. In view of the oxidation state of Bi3+, Fe2+, Ti4+, and O2− from the orbital-resolved density of states of the Bi-6p, Fe-3d, Ti-3d, and O-2p states, the valence state of Bi2FeTiO6 in the rhombohedral phase was found to be Bi3+2Fe2+Ti4+O6.