Electronic Ferroelectricity and Frustration

TL;DR

This paper reviews electronic ferroelectricity, emphasizing how electronic interactions and frustration, especially in spin and charge systems, lead to novel ferroelectric phenomena in multiferroic materials.

Contribution

It provides a comprehensive overview of electronic ferroelectricity driven by frustration, highlighting recent experimental and theoretical advances in spin and charge systems.

Findings

Spin frustration is crucial for spin-driven ferroelectricity.

Charge order and fluctuations induce electric polarization.

Layered iron oxides exhibit exotic dielectric properties.

Abstract

Beyond a conventional classification of ferroelectricity, there is a class of materials where electronic degrees of freedom and electronic interactions are directly responsible for electric polarization and ferroelectric transition. This is termed electronic ferroelectricity. In this article, we review electronic ferroelectricity from a view point of frustration. Experimental and theoretical examinations in spin driven ferroelectric materials, recently termed multiferroics, are introduced. Spin frustration caused by competing magnetic interactions is of prime importance for this type of ferroelectricity. Charge driven ferroelectricity where electronic charge order induces electric polarization is reviewed. In particular, exotic dielectric and magneto-dielectric properties in layered iron oxides are focused on. Through a number of recent experimental and theoretical researches, charge fluctuation due to frustrated geometry plays essential roles on electronic ferroelectricity in this compound.