title: Long-range magnetic coupling across a polar insulating layer.
abstract: Magnetic interactions in solids are normally mediated by short-range exchange or weak dipole fields. Here we report a magnetic interaction that can propagate over long distances (∼10 nm) across a polar insulating oxide spacer. Evidence includes oscillations of magnetization, coercivity and field-cooled loop shift with the thickness of LaAlO3 in La0.67Sr0.33MnO3/LaAlO3/SrTiO3 heterostructures. Similar modifications of the hysteresis loop appear when two coupled films of La0.67Sr0.33MnO3 are separated by LaAlO3, or another polar insulator, but they are absent when the oxide spacer layer is nonpolar. The loop shift is attributed to strong spin-orbit coupling and Dzyaloshinskii-Moriya interaction at the interfaces. There is evidence from inelastic light scattering that the polar spacer mediates long-range transmission of orbital magnetization. This coupling mechanism is expected to apply for any conducting ferromagnetic oxide with mixed valence; in view of electron hopping frequency involved, it raises the prospect of terahertz tunability of magnetic coupling.
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.
authors.forename: W M
authors.initials: WM
authors.lastname: Lü
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Surajit
authors.initials: S
authors.lastname: Saha
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: X Renshaw
authors.initials: XR
authors.lastname: Wang
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Liu
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.
authors.forename: K
authors.initials: K
authors.lastname: Gopinadhan
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: A
authors.initials: A
authors.lastname: Annadi
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.forename: S W
authors.initials: SW
authors.lastname: Zeng
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.
authors.forename: Z
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore.
authors.forename: B C
authors.initials: BC
authors.lastname: Bao
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore.
authors.forename: C X
authors.initials: CX
authors.lastname: Cong
authors.affiliation: Department of Pure and Applied Physics, Trinity College, Dublin 2, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Venkatesan
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Science, Nanyang Technological University, Singapore 637371, Singapore.
authors.forename: T
authors.identifier: http://orcid.org/0000-0002-0113-2895
authors.initials: T
authors.lastname: Yu
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Pure and Applied Physics, Trinity College, Dublin 2, Ireland.
authors.forename: J M D
authors.initials: JMD
authors.lastname: Coey
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.
authors.identifier: http://orcid.org/0000-0002-0598-426X
authors.lastname: Ariando
authors.affiliation: NUSNNI-Nanocore, National University of Singapore, Singapore 117411, Singapore.|Department of Physics, National University of Singapore, Singapore 117542, Singapore.|Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore.
authors.forename: T
authors.initials: T
authors.lastname: Venkatesan