Fishtail effect and the vortex phase diagram of high-entropy alloy superconductor

High-entropy alloy (HEA) is an attracting topic raising in materials science and condensed matter physics. Although several types of superconductors have been discovered HEAs, the critical currents (Jc) HEA remain uncharacterized up to now. Here, we systematically study current-carrying ability (TaNb)0.7(HfZrTi)0.5 at various heat treatment conditions. We obtained high upper field large current carrying ability, which point optimistic applications. Interestingly, fishtail or second peak effect was found for first time superconductors, position vortex pinning force shows a maximum 0.72 reduced field, quite different from cuprates iron-based high-Tc superconductors. Together with resistive measurements, phase diagram superconductor.