Ab initio prediction of coexistence of ferrimagnetism and ferroelectricity in rhombohedral Bi2FeNiO6

First-principles calculations within local spin density approximation (LSDA)+U show that Bi2FeNiO6, as a potential multiferroic, possess ferrimagnetization as large as 1.86μB1.86μB per formula unit with a relatively higher magnetic ordering temperature and a spontaneous polarization of 23.05μC/cm2 caused mainly by the ferroelectric distortions of stereochemically active lone pair of Bi-6s2. In view of the orbital-resolved density of states (ODOS) of the Fe-3d and Ni-3d states, Fe and Ni experience charge disproportionation, as 2M3+>Fe3−δ+Ni3+δ2M3+>Fe3−δ+Ni3+δ, in Bi2FeNiO6 in the rhombohedral phase.