Fabrication of high-entropy alloy superconducting thin films via pulsed laser deposition technique

We fabricate high-entropy alloy (HEA) Ta1/6Nb2/6Hf1/6Zr1/6Ti1/6 superconducting (SC) thin films via a pulsed laser deposition method. Two targets are prepared using arc melting, each followed by sintering at different temperatures: 550°C and 700°C for 12 hours. The films, HEA550 and HEA700, are deposited on c-cut Al2O3 substrates at a substrate temperature of 520°C, using the targets sintered at 550°C and 700°C, respectively. The SC transition temperature (Tc) of HEA700 is 6.88 K, slightly higher than that of HEA550 (= 6.27 K). Both films exhibit similar upper critical field (Hc2) at 0 K, with 11.34 T for HEA550 and 11.40 T for HEA700. Notably, HEA700 exhibits a large critical current density (Jc) of approximately 4.4 MA/cm2 and 3.5 MA/cm2 at 2.0 K and 4.2 K, respectively, accompanying by a predominance of normal point pinning. These results indicate that the targets prepared by arc melting are beneficial for achieving a large Jc in HEA SC thin films, thus providing new avenues for improving SC critical properties of HEA thin films for their practical applications. © 2024, Korea Institute of Applied Superconductivity and Cryogenics. All rights reserved.