Flux Pinning Properties in Low Magnetic Fields of YBa₂Cu₃O_y Thin Films Doped with a Small Amount of BaHfO₃

Abstract

We focused on an improvement of J_c in low magnetic fields (including self-field) for applications to operations in low magnetic fields such as power cables and fault current limiters. We assumed that motion of the fluxes leads to a degradation of J_c even in low magnetic fields. In order to improve the J_c in low magnetic fields, we introduced a small amount of BHO as artificial pinning centers to YBCO thin films and evaluated the superconducting properties. We fabricated BHO-doped YBCO thin films on IBAD-MgO substrates using the pulsed laser deposition method and an excimer laser. The additive amount of BHO was in the range of 0.21 – 3.37 vol.%. The T_c of all the samples was approximately 88 K and this T_c was reduced approximately 1 K compared with the value for a pure-YBCO thin film. On the other hand, J_c at 77 K in the self-field (J_c^self) of 0.42 vol.% BHOdoped samples was 5.76 MA/cm². These values were higher than the J_c^self (3.68 MA/cm²) of the pure-YBCO thin film. In addition, increasing J_c^self improved the J_c in low magnetic fields below 1 T.