title: Direct observation of ferroelectric field effect and vacancy-controlled screening at the BiFeO3/LaxSr1-xMnO3 interface.
abstract: The development of interface-based magnetoelectric devices necessitates an understanding of polarization-mediated electronic phenomena and atomistic polarization screening mechanisms. In this work, the LSMO/BFO interface is studied on a single unit-cell level through a combination of direct order parameter mapping by scanning transmission electron microscopy and electron energy-loss spectroscopy. We demonstrate an unexpected ~5% lattice expansion for regions with negative polarization charge, with a concurrent anomalous decrease of the Mn valence and change in oxygen K-edge intensity. We interpret this behaviour as direct evidence for screening by oxygen vacancies. The vacancies are predominantly accumulated at the second atomic layer of BFO, reflecting the difference of ionic conductivity between the components. This vacancy exclusion from the interface leads to the formation of a tail-to-tail domain wall. At the same time, purely electronic screening is realized for positive polarization charge, with insignificant changes in lattice and electronic properties. These results underline the non-trivial role of electrochemical phenomena in determining the functional properties of oxide interfaces. Furthermore, these behaviours suggest that vacancy dynamics and exclusion play major roles in determining interface functionality in oxide multilayers, providing clear implications for novel functionalities in potential electronic devices.
authors.affiliation: 1] Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-333, Korea.
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kim
authors.affiliation: Institute of Physics, National Academy of Sciences of Ukraine, 46, pr. Nauki, 03028 Kiev Ukraine.
authors.forename: Anna
authors.initials: A
authors.lastname: Morozovska
authors.affiliation: Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3, Krjijanovskogo, 03142 Kiev, Ukraine.
authors.forename: Eugene
authors.initials: E
authors.lastname: Eliseev
authors.affiliation: 1] Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Oxley
authors.affiliation: 1] Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Rohan
authors.initials: R
authors.lastname: Mishra
authors.affiliation: Department of Materials Science and Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Sverre M
authors.initials: SM
authors.lastname: Selbach
authors.affiliation: Department of Materials Science and Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Tor
authors.initials: T
authors.lastname: Grande
authors.affiliation: 1] Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Pantelides
authors.affiliation: The Center for Nanophase Materials Sciences. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Kalinin
authors.affiliation: Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Albina Y
authors.initials: AY
authors.lastname: Borisevich