Magnetic properties of CoFeB films in the ultrathin limit

ORAL

Abstract

In magnetic memory applications, among the critical material parameters that impact device performance are the magnetic moment, the magnetic anisotropy, the Gilbert damping, and the Heisenberg exchange parameter. The Heisenberg exchange is one quantity for which there has been disagreement about how to obtain reliable values in ultrathin films.

In this work, we use Brillouin light scattering (BLS) measurements to map the spin wave manifold of ultrathin CoFeB films to determine the Heisenberg exchange parameter. This method is an extension of previous BLS measurements on thicker films [1]. For films with thicknesses ranging from 1.1 to 1.9 nm, we obtain values of the exchange parameter Aex ranging from approximately 0.5–10 pJ/m (compare to bulk value of ~27.5 pJ/m [2]) and observe a trend where Aex decreases with film thickness. We also determine the exchange parameter using magnetometry and compare to our BLS measurements. Our work establishes a method for determining the exchange parameter in application-relevant ultrathin films and demonstrates that it can deviate significantly from the bulk value in the ultrathin limit.

1. Riley et al., Appl. Phys. Lett., Vol. 120, p.112405 (2020)

2. Devolder et al., J. Appl. Phys., Vol. 120, p.183902 (2016)

*This work was performed with funding from the CHIPS Metrology Program, part of CHIPS for America, National Institute of Standards and Technology, U.S. Department of Commerce.

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Presenters

  • William K Peria

    • Applied Physics Division, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)

Authors

  • William K Peria

    • Applied Physics Division, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)

  • Jacob J Wisser

    • Applied Physics Division, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)

  • Charles Swindells

    • Associate, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)

  • Michael Tanksalvala

    • National Institute of Standards and Technology (NIST)

  • Martina Kiechle

    • National Institute of Standards and Technology (NIST)

  • Guohan Hu

    • IBM Thomas J. Watson Research Center

  • Matthew R Pufall

    • Applied Physics Division, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)

  • Hans T Nembach

    • Applied Physics Division, Physical Measurement Laboratory, NIST, Boulder, CO
    • National Institute of Standards and Technology (NIST)