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Stabilization of the hcp structure in the ruthenium-substituted high-entropy Cantor alloys Cr20Mn20(Fe20−xRux)Co20Ni20 (0 ≤ x ≤ 20) and their magnetic and structural properties

Yaşar Orbay1, David Koch2, Benedikt Eggert3, Aslı Çakır1, Katharina Ollefs4, Heiko Wende3, Michael Farle3, and Mehmet Acet3

  • 1Department of Metallurgical and Materials Engineering, Muğla Sıtkı Koçman University, 48000 Muğla, Turkey
  • 2Fachbereich Material und Geowissenschaften, TU-Darmstadt, D-64287 Darmstadt, Germany
  • 3Faculty of Physics and Center for Nanointegration (CENIDE), Universität Duisburg-Essen, D-47048 Duisburg, Germany
  • 4Kirchhoff Institut für Physik, Universität Heidelberg, 69120 Heidelberg, Germany

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Phys. Rev. B 114, 024401 – Published 6 July, 2026

DOI: https://doi.org/10.1103/3p5b-qlgx

Abstract

While the valence electron concentration (VEC) of the system Cr20Mn20(Fe20−xRux)Co20Ni20 (0≤x≤20), where Fe is partially substituted by Ru, remains at eight electrons per atom (e/a), the structure undergoes a change from single-phase fcc (x=0) to a two-phase fcc/hcp system as x increases, with the VEC of both phases remaining at or very close to 8 e/a. The hcp phase forms already at 5 at% Ru substitution. From studies on thermal expansion determined through x-ray diffraction, magnetization, and Mössbauer spectroscopy, we find that the fcc phase is magnetically active and possesses moment-volume instabilities with energetically close-lying low-spin and high-spin states, while the hcp phase is nonmagnetic in accordance with the predictions of theory. The results show that the hcp phase can be stabilized at a volume fraction of up to 80% under ambient conditions in a predominantly 3-d alloy with VEC=8 e/a.

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Phys. Rev. B 114, 024401– Published 6 July, 2026
  • Received 11 October 2025
  • Revised 7 April 2026
  • Accepted 9 June 2026
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