Quantifying Magnetic Exchange using Brillouin Light Scattering, Magnetometry and Atomistic Simulations

ORAL

Abstract

Exchange stiffness is a fundamental parameter underpinning many magnetic phenomena. The emergent response arising from this local interaction governs key device-level metrics such as domain wall velocity1 and switching probabilities in MRAM cells2, while any micromagnetic simulator requires it to produce accurate results. However, open questions remain regarding how best to quantify exchange stiffness in magnetic thin films. Measuring exchange in samples a few nanometers thick is difficult – usually it is inferred from a global material property. State of the art neutron scattering measurements, typically the gold standard in extracting exchange, are not feasible on the nanoscale due to the low sample volume and polycrystalline films. Another common method is to fit a Bloch T3/2 relation to the temperature profile of the magnetization; however, this is only valid at low temperatures3 and relies on several parameters not easily determined in thin films. While fitting the spin wave dispersion obtained using Brillouin Light Scattering (BLS)4 can overcome these issues, it is not a technique readily available to most. To be able to quantify exchange in a timely and effective manner, we require a method compatible with existing measurement techniques.

Here, we show a method to determine the exchange parameter, by using atomistic simulations5 to quantitatively model temperature dependent magnetization data. For thin film magnetic systems, we explore the landscape of three fitting parameters, exchange, moment and the anisotropy constant. We then compare these results to parameters obtained using BLS7 to determine the impact of the assumed lattice structure on the exchange determination. This method allows for quick determination of key material parameters from blanket films and has significant implications for both future simulations and accelerated device development.

1 D. Kumar et al., Phys. Rep. 958 (2022)

2 T. Santos et al., J. Appl. Phys. 128, 113904 (2020)

3 J. Barker et al Phys. Rev. B 100, 140401(R) (2019)

4 G. Riley et al., Appl. Phys. Lett. 120, 112405 (2022)

5 J. Barker et al Electron. Struct. 2 044002 (2020)

*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

  • Charles Swindells

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

Authors

  • Charles Swindells

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

  • William K Peria

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

  • Joseph Barker

    • University of Leeds

  • Jacob J Wisser

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

  • Michael L Schneider

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

  • 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)