Non-$d^0$ Mn-driven ferroelectricity in antiferromagnetic BaMnO$_3$

By James M. Rondinelli, Aaron S. Eidelson, N. Spaldin. 2009

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Using first-principles density-functional theory we predict a ferroelectric ground state\char22{}driven by the off-centering of the magnetic ${\text{Mn}}^{4+}$ ion\char22{}in perovskite-structure ${\text{BaMnO}}_{3}$. 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 $B$ site for nonmagnetic ${d}^{0}$ 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 $12.8\text{ }\ensuremath{\mu}\text{C}/{\text{cm}}^{2}$. 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.

Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/ff08cdbc6957649e9c1700467d17a679fe8a2172