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Optimization of Nanocomposite Materials for Permanent Magnets: Micromagnetic Simulations of the Effects of Intergrain Exchange and the Shapes of Hard Grains

Sergey Erokhin and Dmitry Berkov*

  • General Numerics Research Lab, Moritz-von-Rohr-Strasse 1A, D-07749 Jena, Germany

  • *d.berkov@general-numerics-rl.de
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Phys. Rev. Applied 7, 014011 – Published 17 January, 2017

DOI: https://doi.org/10.1103/PhysRevApplied.7.014011

Abstract

In this paper, we perform a detailed numerical analysis of remagnetization processes in nanocomposite magnetic materials consisting of magnetically hard grains (i.e., grains made of a material with a high magnetocrystalline anisotropy) embedded into a magnetically soft phase. Such materials are widely used for the production of permanent magnets because they combine high remanence with large coercivity. We perform simulations of nanocomposites with Sr-ferrite as the hard phase and Fe or Ni as the soft phase, concentrating our efforts on analyzing the effects of (i) the imperfect intergrain exchange and (ii) the nonspherical shape of hard grains. We demonstrate that—in contrast to common belief—the maximal energy product is achieved not for systems with a perfect intergrain exchange, but for materials where this exchange is substantially weakened. We also show that the main parameters of the hysteresis loop—remanence, coercivity, and the energy product—exhibit nontrivial dependencies on the shape of hard grains and provide detailed explanations for our results. Simulation predictions obtained in this work open new ways for the optimization of materials for permanent magnets.

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Phys. Rev. Applied 7, 014011– Published 17 January, 2017
  • Received 22 August 2016

© 2017 American Physical Society

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