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Full-spin-wave-scaled stochastic micromagnetism for mesh-independent simulations of ferromagnetic resonance and reversal

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Author(s)

  • Harald Oezelt
  • Luman Qu
  • Alexander Kovacs
  • Johann Fischbacher
  • Markus Gusenbauer
  • Roman Beigelbeck
  • Dirk Praetorius
  • Masao Yano
  • Tetsuya Shoji
  • Akira Kato
  • Roy Chantrell
  • Michael Winklhofer
  • Gergely T. Zimanyi
  • Thomas Schrefl

Department/unit(s)

Publication details

Journalnpj Computational Materials
DateAccepted/In press - 25 Jan 2022
DatePublished (current) - 8 Mar 2022
Issue number1
Volume8
Number of pages9
Original languageEnglish

Abstract

In this paper, we address the problem that standard stochastic Landau-Lifshitz-Gilbert (sLLG) simulations typically produce results that show unphysical mesh-size dependence. The root cause of this problem is that the effects of spin-wave fluctuations are ignored in sLLG. We propose to represent the effect of these fluctuations by a full-spin-wave-scaled stochastic LLG, or FUSSS LLG method. In FUSSS LLG, the intrinsic parameters of the sLLG simulations are first scaled by scaling factors that integrate out the spin-wave fluctuations up to the mesh size, and the sLLG simulation is then performed with these scaled parameters. We developed FUSSS LLG by studying the Ferromagnetic Resonance (FMR) in Nd2Fe14B cubes. The nominal scaling greatly reduced the mesh size dependence relative to sLLG. We then performed three tests and validations of our FUSSS LLG with this modified scaling. (1) We studied the same FMR but with magnetostatic fields included. (2) We simulated the total magnetization of the Nd2Fe14B cube. (3) We studied the effective, temperature- and sweeping rate-dependent coercive field of the cubes. In all three cases, we found that FUSSS LLG delivered essentially mesh-size-independent results, which tracked the theoretical expectations better than unscaled sLLG. Motivated by these successful validations, we propose that FUSSS LLG provides marked, qualitative progress towards accurate, high precision modeling of micromagnetics in hard, permanent magnets.

Bibliographical note

Funding Information:
This work is based on results obtained from the future pioneering program ?Development of magnetic material technology for high-efficiency motors? commissioned by the New Energy and Industrial Technology Development Organization (NEDO). The financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development, and the Christian Doppler Research Association are gratefully acknowledged. The authors acknowledge the financial support by the Vienna Science and Technology Fund (WWTF) under grant MA141-044.

Funding Information:
This work is based on results obtained from the future pioneering program ‘Development of magnetic material technology for high-efficiency motors’ commissioned by the New Energy and Industrial Technology Development Organization (NEDO). The financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development, and the Christian Doppler Research Association are gratefully acknowledged. The authors acknowledge the financial support by the Vienna Science and Technology Fund (WWTF) under grant MA141-044.

Publisher Copyright:
© 2022, The Author(s).

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