Abstract
In perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in with an structure [1] but suppress ferroelectricity in with a symmetry [2]. For many -like perovskites, the structure is a metastable phase. Here, we report the stabilization of the highly polar -like phase of in a superlattice grown on a substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk to a different pattern that is characteristic of a phase. The reconstruction is interpreted through a combination of amplitude-contrast sub-0.1-nm high-resolution transmission electron microscopy and first-principles theories of the structure, energetics, and polarization of the superlattice and its constituents. We further predict a number of new artificial ferroelectric materials demonstrating that nonpolar perovskites can be turned into ferroelectrics via this interface mechanism. Therefore, a large number of perovskites with the structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].
- Received 13 July 2015
- Corrected 25 March 2016
DOI:https://doi.org/10.1103/PhysRevX.6.011027
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Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
25 March 2016
Viewpoint
When One Plus One is More than Two
Published 14 March 2016
Simulations show that the interface between two perovskite oxides can be a much stronger ferroelectric than either oxide on its own.
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Popular Summary
Ferroelectricity, a property of materials with a spontaneous electric polarization that can be switched in an applied electric field, is a desired functionality in oxide materials. In the ground state, each bulk perovskite adopts a particular pattern of oxygen octahedron rotation in accordance with its chemical elements. In -type perovskites, the pattern of oxygen octahedron rotation encourages the development of large ferroelectricity. However, in -type perovskites, this same pattern suppresses ferroelectricity. Unfortunately, -type perovskites are much more common in nature than -type perovskites. Using modern thin-film technology, the layer-by-layer growth of perovskite superlattices provides an opportunity not only to modify but also to fundamentally change the pattern of oxygen octahedron rotation to overcome this limitation set by nature. Here, we show that oxygen octahedron rotation of -type perovskites can be stabilized in at the interface in superlattices.
We use a superlattice grown on a substrate, and we conduct our experiments at room temperature (300 K). Our analysis relies on a combination of first-principles-based theories and amplitude-contrast, high-resolution transmission electron microscopy with a resolution better than 0.1 nm. By considering the oxygen octahedron rotation to be a controllable parameter, our discovery establishes a novel interface approach to induce ferroelectricity in perovskites. Our first-principles calculations show that nonpolar perovskites can be stabilized to have a -type oxygen octahedron rotation pattern with a large ferroelectric polarization when the -type structure is favored.
We expect that our findings will pave the way for studies of room-temperature multiferroic materials important in the electronics industry.