First-principles investigation of ferromagnetism and ferroelectricity in bismuth manganite

We present results of local spin density approximation (LSDA) pseudopotential calculations for the perovskite structure oxide, bismuth manganite (BiMnO₃). The origin of the differences between bismuth manganite and other perovskite manganites is determined by first calculating total energies and band structures of the high symmetry cubic phase, then sequentially lowering the magnetic and structural symmetry. Our results indicate that covalent bonding between bismuth cations and oxygen anions stabilizes different magnetic and structural phases compared with the rare earth manganites. This is consistent with recent experimental results showing enhancement of charge ordering in doped bismuth manganite.