Low Damping in Spinel Ferrite Thin Films Enabled by Chemical Substitution

ORAL

Abstract

Spinel ferrites are versatile magnetic insulators whose properties can be tuned by chemical substitution of their constituent elements. However, it has been a challenge to realize spinel ferrite thin films with sufficiently low damping for emerging spintronic applications. We achieve low damping in spinel ferrite films by substituting a large fraction of Fe with Al. Films of thickness $\approx $25 nm and nominal compositions Ni$_{\mathrm{0.65}}$Zn$_{\mathrm{0.35}}$Al$_{\mathrm{x}}$Fe$_{\mathrm{2-x}}$O$_{\mathrm{4}}$ are grown on single-crystal MgAl$_{\mathrm{2}}$O$_{\mathrm{4}}$(001) substrates by pulsed laser deposition. Fully coherent growth of Ni-Zn ferrite (x$=$0) on MgAl$_{\mathrm{2}}$O$_{\mathrm{4}}$ is elusive due to the large substrate-film lattice mismatch of \textgreater 3{\%}. High concentrations of Al (x$\ge $0.5) decrease the lattice constant of the ferrite such that the films are fully strained to the substrate and highly crystalline. As the Al concentration is increased from x$=$0.5 to 1.0, the Gilbert damping parameter $\alpha $ is reduced from $\approx $0.02 to $\approx $0.005, lower than $\alpha $ of permalloy. These low-damping spinel ferrite thin films facilitate the development of new spintronic devices based on insulating oxides.

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Authors

  • Satoru Emori

    Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, Stanford University

  • Matthew Gray

    Department of Materials Science and Engineering, Stanford University, Stanford CA, Stanford University

  • Samuel Crossley

    Department of Applied Physics, Stanford University, Stanford, California 94305, USA, Stanford University

  • Urusa Alaan

    Stanford University

  • Adrian Swartz

    Stanford University

  • Benjamin Gray

    Air Force Research Laboratory

  • Hyung-Min Jeon

    Department of Electrical Engineering, Wright State University, Dayton, OH, Wright State University

  • Harold Hwang

    Stanford and SLAC, Stanford University

  • Brandon Howe

    Air Force Research Laboratory

  • Yuri Suzuki

    Department of Applied Physics, Stanford University, Stanford CA, Department of Applied Physics, Stanford University, Stanford University