Biskyrmion bubble lattice in Fe/Gd alloy thin films

ORAL

Abstract

Magnetic bubbles with topologically non-trivial twists, called ``skyrmion bubbles,'' exhibit particle-like properties and novel magnetic interactions with each other. They are seen in non-centrosymmetric crystals, such as MnSi, and monolayers of Fe on Ir(111) substrates. Our study considers whether skyrmion bubbles can also form in soft ferrimagnetic alloys with perpendicular anisotropy. Using resonant x-ray scattering at the Fe L$_3$ and Gd M$_5$ transition edges, we show that triangular lattices of skyrmion bubbles form in Fe/Gd thin films in a limited temperature and magnetic field range. Uniaxial anisotropy in the resonant scattering pattern indicates the lattice unit cell contains two skyrmions. Lorentz TEM images reveal that the repeating unit is a bound pair of bubbles called \textit{biskyrmions}. Adjusting the composition of the films can shift the temperature range of the biskyrmion lattice by 100 K, allowing the lattice to form at room temperature. Fe/Gd thin films may prove a promising material for spintronics.

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Authors

  • James Lee

    • Lawrence Berkeley National Laboratory and University of Oregon, Eugene
    • Advanced Light Source, Lawrence Berkeley National Laboratory \& Deptartment of Physics, University of Oregon
    • Lawrence Berkeley National Laboratory

  • Xiaowen Shi

    • University of Oregon, Eugene

  • Jordan Chess

    • University of Oregon, Eugene

  • Sergio Montoya

    • Center for Magnetic Recording Research, University of California, San Diego

  • Shrawan Mishra

    • Lawrence Berkeley National Laboratory

  • Lev Sakharov

    • University of Oregon, Eugene

  • Daniel Parks

    • Lawrence Berkeley National Laboratory

  • Ben McMorran

    • University of Oregon, Eugene

  • Steven Kevan

    • Lawrence Berkeley National Laboratory and University of Oregon, Eugene

  • Eric Fullerton

    • Center for Magnetic Recording Research, University of California, San Diego

  • Sujoy Roy

    • Lawrence Berkeley National Laboratory