Observation of magnetic vortex pairs at room temperature in a planar α-Fe<sub>2</sub>O<sub>3</sub>/Co heterostructure

 · Invited

Abstract

Vortices, occurring whenever a flow field ‘whirls’ around a one-dimensional core, are among the simplest topological structures, ubiquitous to many branches of physics. In the crystalline state, vortex formation is rare, since it is generally hampered by long-range interactions: in ferroic materials (ferromagnetic and ferroelectric), vortices are observed only when the effects of the dipole–dipole interaction are modified by confinement at the nanoscale, or when the parameter associated with the vorticity does not couple directly with strain. We observed an unprecedented form of vortices in antiferromagnetic haematite (α-Fe2O3) epitaxial films, in which the primary whirling parameter is the staggered magnetization [1]. Remarkably, ferromagnetic topological objects with the same vorticity and winding number as the α-Fe2O3 vortices are imprinted onto an ultra-thin Co ferromagnetic over-layer by interfacial exchange. Our data, supported by mirco-magnetic modelling, suggest that the ferromagnetic vortices may be merons (half-skyrmions, carrying an out-of plane core magnetization), and indicate that the vortex/meron pairs can be manipulated by the application of an in-plane magnetic field, giving rise to large-scale vortex–antivortex annihilation.

[1] F.P. Chmiel et al., Nature Materials 17, 581–585 (2018)

*We acknowledge EPSRC grants No. EP/M020517/1, and Army Research Office grant W911NF-13-1-0486 for work at Oxford and Madison, respectively, and the Diamond Light Source beamtime on I06.

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Presenters

  • Paolo G. Radaelli

    • Physics, University of Oxford
    • Clarendon Laboratory, University of Oxford
    • University of Oxford

Authors

  • Paolo G. Radaelli

    • Physics, University of Oxford
    • Clarendon Laboratory, University of Oxford
    • University of Oxford

  • Francis Chmiel

    • Clarendon Laboratory, University of Oxford

  • Noah Waterfield Price

    • Clarendon Laboratory, University of Oxford

  • Roger Johnson

    • University of Oxford
    • ISIS Pulsed Neutron Source, Rutherford Appleton Laboratory
    • Clarendon Laboratory, University of Oxford
    • Department of Physics, University of Oxford
    • Physics, University of Oxford

  • Anne D Lamirand

    • Diamond Light Source, Didcot, UK

  • Jonathon L Schad

    • Department of Materials Science and Engineering, University of Wisconsin-Madison

  • Gerrit Van der Laan

    • Diamond Light Source, Didcot, UK

  • David T Harris

    • Department of Materials Science and Engineering, University of Wisconsin-Madison

  • Julian J Irwin

    • Department of Physics, University of Wisconsin-Madison

  • Mark S Rzchowski

    • Department of Physics, University of Wisconsin-Madison

  • Chang-Beom Eom

    • Department of Materials Science and Engineering, University of Wisconsin–Madison
    • Department of Materials Science and Engineering, University of Wisconsin-Madison
    • University of Wisconsin-Madison
    • Department of Material Science and Engineering, University of Wisconsin-Madison
    • Materials Science and Engineering, University of Wisconsin-Madison
    • Materials Science and Engineering, Univ of Wisconsin-Madison
    • University of Wisconsin–Madison