We show that electronic correlations decimate the intrinsic ferroelectric polarization of the recently discovered class of multiferroic manganites RMn2O5, where R is a rare earth element. Such is manifest from {\it ab initio} bandstructure computations that account for the strong local Coulomb interactions between the manganese 3d electrons --the root of magnetism in these materials. When including these the computed electronic, magnetic and lattice structure of multiferroic HoMn2O5 results in an amplitude and direction of polarization that is in accordance with experiment. The microscopic mechanism behind the decimation is a near cancellation of the ionic polarization induced by ferroelectric lattice displacements and the electronic one caused by valence charge redistributions.
@article{arxiv.0802.0653,
title = {Electronic correlations decimate the ferroelectric polarization of multiferroic HoMn2O5},
author = {Gianluca Giovannetti and Jeroen van den Brink},
journal= {arXiv preprint arXiv:0802.0653},
year = {2009}
}