Superlattice-induced ferroelectricity in charge-ordered La1/3Sr2/3FeO3

Se Young Park; Karin M. Rabe; Jeffrey B. Neaton

doi:10.1073/pnas.1906513116

New Research In

Contributed by Karin M. Rabe, October 14, 2019 (sent for review May 17, 2019; reviewed by Steven May and Silvia Picozzi)

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Significance

Charge-order–driven ferroelectrics are an emerging class of materials with promise for high-frequency electron-dominated polarization switching, distinct from conventional ferroelectrics. However, only a few systems exhibiting this behavior have been experimentally realized thus far. With continued development of layer-by-layer growth techniques with a high level of composition control, the exploration of charge-ordered ferroelectrics can be extended to artificially structured superlattices. Here, we use density-functional theory to explore an experimentally realized bulk perovskite iron-oxide solid solution with robust charge ordering and find that in superlattices formed by layered cation ordering, bulk charge ordering is maintained and can lead to charge-order–driven ferroelectricity. Our results suggest that other broad classes of mixed valence materials may be promising candidates for discovery of electronic ferroelectrics.

Abstract

Charge-order–driven ferroelectrics are an emerging class of functional materials, distinct from conventional ferroelectrics, where electron-dominated switching can occur at high frequency. Despite their promise, only a few systems exhibiting this behavior have been experimentally realized thus far, motivating the need for new materials. Here, we use density-functional theory to study the effect of artificial structuring on mixed-valence solid-solution La_1/3Sr_2/3FeO₃ (LSFO), a system well studied experimentally. Our calculations show that A-site cation (111)-layered LSFO exhibits a ferroelectric charge-ordered phase in which inversion symmetry is broken by changing the registry of the charge order with respect to the superlattice layering. The phase is energetically degenerate with a ground-state centrosymmetric phase, and the computed switching polarization is 39 μC/cm2, a significant value arising from electron transfer between FeO6 octahedra. Our calculations reveal that artificial structuring of LSFO and other mixed valence oxides with robust charge ordering in the solid solution phase can lead to charge-order–induced ferroelectricity.

Footnotes

↵¹To whom correspondence may be addressed. Email: kmrabe{at}physics.rutgers.edu.

Author contributions: S.Y.P., K.M.R., and J.B.N. designed research; S.Y.P. performed research; and S.Y.P., K.M.R., and J.B.N. wrote the paper.
Reviewers: S.M., Drexel University; and S.P., Consiglio Nazionale delle Ricerche - SuPerconducting and other INnovative materials and devices institute (CNR-SPIN).
The authors declare no competing interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1906513116/-/DCSupplemental.

Published under the PNAS license.

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