Abstract
Using first-principles density-functional theory we predict a ferroelectric ground state—driven by the off-centering of the magnetic ion—in perovskite-structure . Our finding is surprising since the competition between energy-lowering covalent bond formation and energy-raising Coulombic repulsions usually only favors off-centering on the perovskite site for nonmagnetic ions. We explain this tendency for ferroelectric off-centering by analyzing the changes in electronic structure between the centrosymmetric and polar states and by calculating the Born effective charges; we find anomalously large values for Mn and O consistent with our calculated polarization of . Finally, we suggest possible routes by which the perovskite phase may be stabilized over the usual hexagonal phase to enable a practical realization of a single-phase multiferroic.
- Received 21 January 2009
DOI:https://doi.org/10.1103/PhysRevB.79.205119
©2009 American Physical Society