Abstract
Ab initio calculations of the electric polarization of correlation-driven insulating materials, namely, Mott insulators, are lacking. Using a combination of density-functional theory and dynamical mean-field theory we study the electric polarization of the Mott insulator . We predict a ferroelectric polarization of in the high-temperature paramagnetic phase and recover a measured value of in the low-temperature antiferromagnetic phase. Our calculations reveal that the driving force for the ferroelectricity, the hybridization between Mn and O p orbitals, is suppressed by correlations, in particular, by the Hund's coupling and by the onset of magnetic order. They also confirm that the half-filled Mn orbitals give rise to the antiferromagnetic Mott phase. This magnetic ordering leads to changes in the ionic polar displacement and, in turn, to the electronic polarization. In addition, for a fixed ionic displacement, we find that there is a reduction in the electronic contribution due to partial magnetic polarization of the Mn orbitals. The reduction of the polarization due to ionic displacement dominates over the additional electronic part, hence the net magnetoelectric coupling is negative.
- Received 13 September 2014
- Revised 25 November 2014
DOI:https://doi.org/10.1103/PhysRevB.90.220405
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