Oxygen-Vacancy-Induced Polar Behavior in (LaFeO3)2/(SrFeO3) Superlattices

Title
Oxygen-Vacancy-Induced Polar Behavior in (LaFeO3)2/(SrFeO3) Superlattices
Authors
Rohan MishraYoung-Min KimJuan Salafranca김성근Seo Hyoung ChangAnand BhattacharyaDillon D. FongStephen J. PennycookSokrates T. PantelidesAlbina Y. Borisevich
Keywords
Transition-metal oxides; multiferroics; polar oxides; DFT calculations; oxygen vacancies; scanning transmission electron microscopy
Issue Date
2014-05
Publisher
Nano letters
Citation
VOL 14, NO 5, 2694-2701
Abstract
Complex oxides displaying ferroelectric and/or multiferroic behavior are of high fundamental and applied interest. In this work, we show that it is possible to achieve polar order in a superlattice made up of two nonpolar oxides by means of oxygen vacancy ordering. Using scanning transmission electron microscopy imaging, we show the polar displacement of magnetic Fe ions in a superlattice of (LaFeO3)2/(SrFeO3) grown on a SrTiO3 substrate. Using density functional theory calculations, we systematically study the effect of epitaxial strain, octahedral rotations, and surface terminations in the superlattice and find them to have a negligible effect on the antipolar displacements of the Fe ions lying in between SrO and LaO layers of the superlattice (i.e., within La0.5Sr0.5FeO3 unit cells). The introduction of oxygen vacancies, on the other hand, triggers a polar displacement of the Fe ions. We confirm this important result using electron energy loss spectroscopy, which shows partial oxygen vacancy ordering in the region where polar displacements are observed and an absence of vacancy ordering outside of that area.
URI
http://pubs.kist.re.kr/handle/201004/47591
ISSN
15306984
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KIST Publication > Article
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