Ferroelectricity and multiferroicity in anti-Ruddlesden-Popper structures

TL;DR

This paper identifies a new family of anti-Ruddlesden-Popper phases exhibiting ferroelectricity and anti-ferroelectricity, including hyperferroelectric behavior and coupled magnetic and electric order, through high-throughput phonon analysis.

Contribution

It introduces a novel structural family of ferroelectric materials with unique properties, discovered via high-throughput phonon structure analysis.

Findings

Discovery of anti-Ruddlesden-Popper phases with ferroelectric and anti-ferroelectric behaviors

Identification of hyperferroelectric properties in the new family

Eu4Sb2O exhibits coupled ferromagnetic and ferroelectric order

Abstract

Combining ferroelectricity with other properties such as visible light absorption or long-range magnetic order requires the discovery of new families of ferroelectric materials. Here, through the analysis of a high-throughput database of phonon band structures, we identify a new structural family of anti-Ruddlesden-Popper phases A$_4$X$_2$O (A=Ca, Sr, Ba, Eu, X=Sb, P, As, Bi) showing ferroelectric and anti-ferroelectric behaviors. The discovered ferroelectrics belong to the new class of hyperferroelectrics which polarize even under open-circuit boundary conditions. The polar distortion involves the movement of O anions against apical A cations and is driven by geometric effects resulting from internal chemical strains. Within this new structural family, we show that Eu$_4$Sb$_2$O combines coupled ferromagnetic and ferroelectric order at the same atomic site, a very rare occurrence in materials physics.