Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Xiaofu Zhang; Natascha Winter; Catherine Witteveen; Thomas Moehl; Yuan Xiao; Fabio Krogh; Andreas Schilling; Fabian O. von Rohr

doi:10.1103/PhysRevResearch.2.013375

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Xiaofu Zhang, Natascha Winter, Catherine Witteveen, Thomas Moehl, Yuan Xiao, Fabio Krogh, Andreas Schilling, Fabian O. von Rohr

DOI 10.1103/PhysRevResearch.2.013375 · Physical Review Research

T1

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Abstract

We report on the preparation and the physical properties of superconducting (TaNb)1−x(ZrHfTi)x high-entropy alloy films. The films were prepared by means of magnetron sputtering at room temperature, with x ranging from 0 to 1 with an average thickness of 600–950 nm. All films crystallize in a pseudo body-centered cubic (BCC) structure. For samples with x<0.65, the normal-state properties are metallic, while for x≥0.65 the films are weakly insulating. The transition from metallic to weakly insulating occurs right at the near-equimolar stoichiometry. We find all films, except for x=0 or 1, to become superconducting at low temperatures, and we interpret their superconducting properties within the Bardeen-Cooper-Schrieffer (BCS) framework. The highest transition temperature Tc=6.9K of the solid solution is observed for x∼0.43. The highest upper-critical field Bc2(0)=11.05 T is found for the near-equimolar ratio x∼0.65, where the mixing entropy is the largest. The superconducting parameters derived for all the films from transport measurements are found to be close to those that are reported for amorphous superconductors. Our results indicate that these films of high-entropy alloys are promising candidates for superconducting device fabrication.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(TaNb)0.12(ZrHfTi)0.88 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.77	Pressure not reported	zero_resistance
(TaNb)0.24(ZrHfTi)0.76 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.61	Pressure not reported	zero_resistance
(TaNb)0.35(ZrHfTi)0.65 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.6	Pressure not reported	zero_resistance
(TaNb)0.46(ZrHfTi)0.54 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.14	Pressure not reported	zero_resistance
(TaNb)0.57(ZrHfTi)0.43 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.76	Pressure not reported	zero_resistance
(TaNb)0.67(ZrHfTi)0.33 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.43	Pressure not reported	zero_resistance
(TaNb)0.79(ZrHfTi)0.21 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.23	Pressure not reported	zero_resistance
(TaNb)0.87(ZrHfTi)0.13 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.02	Pressure not reported	zero_resistance
(TaNb)0.96(ZrHfTi)0.04 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.57	Pressure not reported	zero_resistance