Magnetic-field angle dependent critical current densities and flux pinning in commercial YBCO tapes below liquid nitrogen temperatures

Abstract

We investigated the magnetic-field angle dependence of critical current densities (Jc) for commercial YBCO and Zr-doped (GdY)BCO tapes fabricated by an MOCVD method at temperatures from 80K down to 20K in fields (μ0H) up to 5T. For the YBCO tape it was observed that the flux pinning contribution from random pins smaller than 2ξ(T) (ξ(T) is the Ginzburg–Landau coherence length at temperature T) diminished as T decreased, while they were still important even at 20K. As the temperature went down, the peaks at H||ab were found to be increasingly sharp, which agrees well with the Tachiki–Takahashi intrinsic pinning model. The Zr-doped (GdY)BCO tape showed peaks near H||c as well as H||ab and exhibited improved in-field Jc properties, compared with the YBCO tape.