Fe, Mn, and Cr doped BiCoO₃ for magnetoelectric application: A first-principles study

The tetragonal compound BiCoO₃ may play a significant role in magnetoelectric devices if its magnetism can be tuned and its strong ferroelectricity maintained. Here we have studied Fe, Mn, and Cr doped BiCoO₃ with a concentration of 12.5% by density functional theory (DFT) and DFT + U calculations. It is found that all the doped magnetic ions favor ferromagnetic coupling in the C-type antiferromagnetic BiCoO₃ lattice, leading to net magnetic moments of 1, 1, 0 μ_B for Bi ₈Co₇XO₂₄, where X = Fe, Cr, and Mn, respectively. Meanwhile, the Berry phase calculations indicate that the strong ferroelectricity is almost preserved for Fe, Cr, and Mn doped BiCoO₃, with values of 172.7, 152.1, and 169.8νCcm^{- 2}, respectively, close to the original polarization value of 174.9 νCcm^{- 2}. As a result, Cr or Fe doping may be useful to make the BiCoO₃ system ferrimagnetic while maintaining its excellent ferroelectric performance.