Strain-induced ferroelectricity in simple rocksalt binary oxides

TL;DR

This study demonstrates that applying epitaxial strain can induce ferroelectricity in simple rocksalt binary oxides like BaO, revealing potential for their use in microelectronics and multiferroic applications.

Contribution

First-principles calculations show strain-induced ferroelectricity in simple binary oxides, expanding the class of materials with functional ferroelectric properties beyond complex perovskites.

Findings

Ferroelectricity can be induced in BaO using epitaxial strain.

Strained binary oxides exhibit polarization and piezoelectric responses comparable to perovskites.

Magnetic binary oxides like EuO also show similar behavior, suggesting multiferroic potential.

Abstract

The alkaline earth binary oxides adopt a simple rocksalt structure and form an important family of compounds because of their large presence in the earth's mantle and their potential use in microelectronic devices. In comparison to the class of multifunctional ferroelectric perovskite oxides, however, their practical applications remain limited and the emergence of ferroelectricity and related functional properties in simple binary oxides seems so unlikely that it was never previously considered. Here, we show using first-principles density functional calculations that ferroelectricity can be easily induced in simple alkaline earth binary oxides such as barium oxide (BaO) using appropriate epitaxial strains. Going beyond the fundamental discovery, we show that the functional properties (polarization, dielectric constant and piezoelectric response) of such strained binary oxides are comparable in magnitude to those of typical ferroelectric perovskite oxides, so making them of direct interest for applications. Finally, we show that magnetic binary oxides such as EuO, with the same rocksalt structure, behave similarly to the alkaline earth oxides, suggesting a route to new multiferroics combining ferroelectric and magnetic properties.