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

Rafał Idczak; Wojciech Nowak; Michał Babij; Daniel Gnida; Robert Konieczny; Monika K. Krawczyk; Dorota Podsiadła; Tomasz Ossowski; Rafał Topolnicki; Adam Pikul

doi:10.1103/fnz7-bzmw

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

Rafał Idczak, Wojciech Nowak, Michał Babij, Daniel Gnida, Robert Konieczny, Monika K. Krawczyk, Dorota Podsiadła, Tomasz Ossowski, Rafał Topolnicki, Adam Pikul

DOI 10.1103/fnz7-bzmw · Physical Review B

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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.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(NbHf)0.75(TiZr)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.4	Pressure not reported	onset
(NbHf)0.75(TiZr)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.15	Pressure not reported	midpoint
(NbZr)0.75(TiHf)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	onset
(NbZr)0.75(TiHf)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.17	Pressure not reported	midpoint
(NbTi)0.75(ZrHf)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.9	Pressure not reported	onset
(NbTi)0.75(ZrHf)0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.76	Pressure not reported	midpoint
Ta0.34Nb0.33Hf0.08Zr0.14Ti0.11 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown