Ferroelectricity in multiferroic magnetite Fe3O4 driven by noncentrosymmetric Fe2+/Fe3+ charge-ordering: First-principles study

TL;DR

This study uses first-principles simulations to demonstrate that improper ferroelectricity in magnetite Fe3O4 is caused by charge-ordering, with polarization resulting from electronic charge shifts between Fe sites, exemplifying electronic ferroelectricity.

Contribution

First-principles calculations reveal charge-ordering as the driver of ferroelectricity in magnetite, providing detailed insights into electronic ferroelectricity mechanisms.

Findings

Polarization values agree with experimental data.

Ferroelectricity is driven by charge shifts between Fe sites.

Electronic ferroelectricity is demonstrated in magnetite.

Abstract

By means of first-principles simulations, we unambiguously show that improper ferroelectricity in magnetite in the low-temperature insulating phase is driven by charge-ordering. An accurate comparison between monoclinic ferroelectric Cc and paraelectric P2/c structures shows that the polarization arises because of "shifts" of electronic charge between octahedral Fe sites, leading to a non-centrosymmetric Fe2+/Fe3+ charge-ordered pattern. Our predicted values for polarization, in good agreement with available experimental values, are discussed in terms of point-charge dipoles located on selected Fe tetrahedra, pointing to a manifest example of electronic ferroelectricity driven by charge rearrangement.