Multiferroic Bi2 NiMnO6 thin films: A computational prediction

We report first-principles calculations for one of the few materials that is believed to be a ferroelectric ferromagnet, Bi2NiMnO6. Our calculations show that, contrary to what has been reported so far, bulk Bi2NiMnO6 does not have a polarization. Instead, like BiMnO3, it crystallizes into a centrosymmetric structure with space group C2/c. We also predict that Bi2NiMnO6 will indeed be a ferroelectric ferromagnet if it is grown as an epitaxial film on a substrate with in-plane square symmetry and a lattice constant around 4 Å, such as BaTiO3 or PbZr1-xTixO3.