Tunable ferroelectricity in artificial tri-layer superlattices comprised of non-ferroic components

TL;DR

This study reveals that artificial tri-layer superlattices made of non-ferroelectric materials can exhibit tunable ferroelectricity and magnetoelectric coupling, driven by interface effects and structural asymmetry.

Contribution

It demonstrates the emergence of ferroelectricity in heterostructures composed solely of non-ferroelectric layers, a novel finding in material engineering.

Findings

Ferroelectricity observed below 40 K in non-ferroelectric layers.

Strong tunability of ferroelectricity by superlattice periodicity.

Magnetoelectric coupling results in 150% magnetic modulation of polarization.

Abstract

Heterostructured material systems devoid of ferroic components are presumed not to display ordering associated with ferroelectricity. In heterostructures composed of transition metal oxides, however, the disruption introduced by an interface can affect the balance of the competing interactions among electronic spins, charges and orbitals. This has led to the emergence of properties absent in the original building blocks of a heterostructure, including metallicity, magnetism and superconductivity. Here we report the discovery of ferroelectricity in artificial tri-layer superlattices consisting solely of non-ferroelectric NdMnO3/SrMnO3/LaMnO3 layers. Ferroelectricity was observed below 40 K exhibiting strong tunability by superlattice periodicity. Furthermore, magnetoelectric coupling resulted in 150% magnetic modulation of the polarization. Density functional calculations indicate that broken space inversion symmetry and mixed valency, because of cationic asymmetry and interfacial polar discontinuity, respectively, give rise to the observed behavior. Our results demonstrate the engineering of asymmetric layered structures with emergent ferroelectric and magnetic field tunable functions distinct from that of normal devices, for which the components are typically ferroelectrics.