Comparison of Different Routes for Improving Vortex Pinning in YBa2Cu3O7 Thin Films and Coated Conductors

Abstract

Achieving high critical currents in YBa2Cu3O7 (YBCO) films on metallic polycrystalline substrates (coated conductors) is an essential step to make coated conductors a technological reality. Therefore it is extremely important to identify the vortex pinning centers responsible for the high critical current density (Jc), to find ways to further improve the vortex pinning in these superconducting films. We present a comparative study of the angular and field dependences of Jc for two successful approaches used to improve vortex pinning, one that introduces correlated defects and another one that increases the random pinning contribution. The correlated defects are obtained by the introduction of BaZrO3 nano‐particles into the superconducting film matrix, which in turn induce c‐axis correlated defects. The enhanced random pinning contribution is achieved by mixing different rare earth. The presence of additional correlated defects results in a slower Jc field decay together with a Jc enhancement around the c‐axis region. The rare earth substitutions yield Jc enhancements at self‐field and at low fields. We show that even though at 75.5 K and intermediate field range both methods produce comparable results, at lower temperatures the correlated defects become more effective pinning the vortices, inducing higher enhancements of Jc.