Vortex Stability and Magnetic Disorder Tolerance in Magnetic High-Entropy Alloy Superconductor NbTaTiZrNi

Abstract

High-entropy alloy (HEA) superconductors offer mechanical robustness and tunable compositions. We report the synthesis and characterization of a Ni-containing HEA, NbTaTiZrNi, which exhibits superconductivity with T c approximate to 7.1 K and weak itinerant ferromagnetism up to 300 K, with coercive fields Hcoer approximate to 100-300 Oe. While magnetic elements often suppress superconductivity via pair breaking, T c in this Ni-containing alloy remains comparable to nonmagnetic Ta1/6Nb2/6Ti1/6Zr1/6Hf1/6 (T c approximate to 7.8 K). Thermomagnetic flux avalanches are not observed, and critical current densities reach 104-105 A cm-2 at 2 K, indicating robust vortex stability in this composition. Electrical resistivity, magnetization, and specific-heat measurements indicate conventional s-wave superconductivity with intermediate electron-phonon coupling (lambda approximate to 0.7). The observed vortex-pinning behavior is consistent with a mixed landscape of grain-boundary and point-like defects, likely influenced by configurational disorder and Ni distribution, though Fe-rich secondary phases may also contribute. These results demonstrate that this specific Ni-containing HEA exhibits robust superconductivity with flux-stable behavior, providing a platform for further exploration of high-performance superconductors in cryogenic applications.