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Cubic magnetic anisotropy in B20 magnets: Interplay of anisotropy and magnetic order in Fe1−xCoxSi

G. Gödecke1,*, A. O. Leonov2,3,†, J. Grefe1, S. Süllow1, and D. Menzel1

  • 1Institut für Physik der Kondensierten Materie, TU Braunschweig, D-38106 Braunschweig, Germany
  • 2Department of Chemistry, Faculty of Science, Hiroshima University Kagamiyama, Higashi Hiroshima, Hiroshima 739-8526, Japan
  • 3International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan

  • *Contact author: g.goedecke@tu-braunschweig.de
  • †Contact author: leonov@hiroshima-u.ac.jp
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Phys. Rev. B 113, 104444 – Published 25 March, 2026

DOI: https://doi.org/10.1103/h76w-8twm

Abstract

The metallic systems MnSi and Fe1−xCoxSi are known to feature a generic magnetic phase diagram primarily determined by the isotropic exchange and Dzyaloshinskii-Moriya interactions. However, additional weaker anisotropies, lowest in the hierarchy of energy scales, play a crucial role: they determine the relative order of phases in the phase diagram and may even enable skyrmion stability far below the ordering temperature. Among cubic B20 helimagnets, the insulator Cu2OSeO3 is currently the only known example exhibiting a low-temperature, anisotropy-induced skyrmion pocket. In this manuscript, we present a systematic study of cubic magnetocrystalline anisotropy by means of angle-resolved SQUID magnetization measurements in MnSi and Fe1−xCoxSi (0.08≤x≤0.70) single crystals and provide quantitative values of the anisotropy constants. For Fe1−xCoxSi, the cubic anisotropy is found to be strongly dependent on the Co concentration x. From a theoretical point of view, for low Co concentrations (x∼0.10), the anisotropy is expected to be sufficiently strong to stabilize a low-temperature skyrmion lattice. Therefore, Fe1−xCoxSi may represent the first chiral metallic system to exhibit a low-temperature skyrmion phase controllably stabilized by cubic anisotropy for specific directions of the magnetic field.

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Phys. Rev. B 113, 104444– Published 25 March, 2026
  • Received 10 October 2025
  • Revised 9 December 2025
  • Accepted 27 February 2026
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