Effect of C additives with 0.5% in weight on structural, optical and superconducting properties of Ta-Nb-Hf-Zr-Ti high entropy alloy films
Tien Le, Yeonkyu Lee, Dzung T. Tran, Woo Seok Choi, Won Nam Kang, Jinyoung Yun, Jeehoon Kim, Jaegu Song, Yoonseok Han, Tuson Park, Duc H. Tran, Soon-Gil Jung, Jungseek Hwang
公開日: 2025/9/25
Abstract
We investigated the superconducting (SC) properties of Ta-Nb-Hf-Zr-Ti high-entropy alloy (HEA) thin films with 0.5% weight C additives. The C additives stabilize the structural properties and enhance the SC critical properties, including $\mu_0$Hc$_2$ (13.45 T) and Tc (7.5 K). The reflectance of the C-added HEA film is enhanced in the low-energy region, resulting in a higher optical conductivity, which is consistent with the lower electrical resistivity. In addition, we observed SC vortices in the C-added HEA film using magnetic force microscopy. The magnetic penetration depths ($\lambda$) of the pure HEA and C-added HEA films were estimated from their Meissner force curves by comparing them with those of a reference Nb film. At 4.2 K, the {\lambda} of the C-added film is 360 nm, shorter than that of the pure HEA film (560 nm), indicating stronger superconductivity against an applied magnetic field.