Strain effects on the electric polarization of BiMnO3

BiMnO3 has long been at the forefront of multiferroics research. Controversy exists, however, over whether it is actually ferroelectric and thus multiferroic, or whether the stereochemically active lone pairs order in an anti-polar centrosymmetric arrangement. Here we investigate the effect of epitaxial strain on the electronic ordering and symmetry of BiMnO3 to determine whether strain effects might explain the apparently contradictory experimental results regarding ferroelectricity. Using ab-initio methods, we calculate the polarization of BiMnO3 under bi-axial strain in the pseudo-cubic (001) plane, examining both tensile and compressive values of strain. We find no significant polarization or re-ordering of Bi lone-pairs under experimentally achievable strain values, and conclude that BiMnO3 remains centrosymmetric and non-polar.