Origin of the multiferroicity in BiMn2O5 from first-principles calculations

Electronic structure, Born effective charges, and spontaneous polarization of multiferroic single crystal BiMn2O5 have been investigated in the framework of density functional theory. The relative stability of the ground state and the origin of multiferroicity for magnetism and ferroelectricity are addressed. The results reveal that the stability of antiferromagnetic (AFM) state is better than the ferromagnetic (FM) and ferrimagnetic configurations. The Born effective charge tensors (Z⁎) have been calculated for this compound using a Berry-phase approach, compared to their nominal ionic values, the Z* of Mn atoms show anomalous difference. By investigating the electric structure of BiMn2O5, there exists obviously hybridization between Bi 6s and O 2p states, our calculations indicate that the 6s2 lone pair on the formally trivalent Bi ion plays an important role in inducing the ferroelectric distortion.

Research highlights
► Single crystal BiMn2O5 had been first reported in Physical Review B (65, (2002) 144423), the dielectric and magnetoelectric properties seem to indicate the possibility of ferroelectricity.
► First, based on density functional theory, we investigate the electronic structure and magnetic properties of this compound, our theoretical results are in good agreement with the experimental data.
► Second, the calculated Born effective charges and spontaneous polarization of BiMn2O5 reveal that this compound shows ferroelectric behavior.
► In addition, by investigating the electric structure of BiMn2O5, there exists obviously hybridization between Bi 6s and O 2p states, our calculations indicate that the 6s2 lone pair on the formally trivalent Bi ion plays an important role in inducing the ferroelectric distortion.