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Violation of Matthias rule: Elemental composition as the key determinant of critical temperature in bcc high-entropy superconductors

Rafał Idczak1,*, Wojciech Nowak1,2, Michał Babij2, Daniel Gnida2, Robert Konieczny1, Monika K. Krawczyk1, Dorota Podsiadła1, Tomasz Ossowski1, Rafał Topolnicki1,3 et al.

Adam Pikul2

  • *Contact author: rafal.idczak@uwr.edu.pl
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Phys. Rev. B 112, 014513 – Published 16 July, 2025

DOI: https://doi.org/10.1103/fnz7-bzmw

Abstract

We systematically investigate three body-centred cubic (bcc) high-entropy alloys (HEAs) with an identical valence electron count (VEC = 4.375): (NbHf)0.75(TiZr)0.25, (NbZr)0.75(TiHf)0.25, and (NbTi)0.75(ZrHf)0.25. Despite their isoelectronic nature, it was found that these alloys exhibit markedly different superconducting properties. Critical temperatures Tc range from 7.14(5) K to 8.17(5) K, while upper critical fields μ0Hc2(0) exceed 12 T, reaching 14.0(9) T for the Ti-rich alloy (NbTi)0.75(ZrHf)0.25. These variations highlight the limited predictive power of the Matthias rule in HEA design. Furthermore, the exceptional properties observed in the Ti-rich composition suggest that Nb and Ti are critical elements for the development of new HEAs for next-generation superconducting magnets.

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Phys. Rev. B 112, 014513– Published 16 July, 2025
  • Received 22 May 2025
  • Accepted 17 June 2025
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