title: Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic.
abstract: Materials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3-the geometric ferroelectric with the greatest known planar rumpling-we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 (refs 17, 18) within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature substantially-from 240 kelvin for LuFe2O4 (ref. 18) to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Mundy
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Brooks
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Holtz
authors.affiliation: Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Jarrett A
authors.initials: JA
authors.lastname: Moyer
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Hena
authors.initials: H
authors.lastname: Das
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Alejandro F
authors.initials: AF
authors.lastname: Rébola
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.|Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48103, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Heron
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Clarkson
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Disseler
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Zhiqi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Farhan
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Rainer
authors.initials: R
authors.lastname: Held
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Hovden
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Elliot
authors.initials: E
authors.lastname: Padgett
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Mao
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Hanjong
authors.initials: H
authors.lastname: Paik
authors.affiliation: Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Misra
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
authors.forename: Lena F
authors.initials: LF
authors.lastname: Kourkoutis
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Elke
authors.initials: E
authors.lastname: Arenholz
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Scholl
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Borchers
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Ratcliff
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.|Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, California 94720, USA.
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Ramesh
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Fennie
authors.affiliation: Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Schiffer
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Muller
authors.affiliation: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.|Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA.
authors.forename: Darrell G
authors.initials: DG
authors.lastname: Schlom