Synergetic Pinning Centers in YBa$_{2}{hbox{Cu}}_{3}{hbox{O}}_{rm x}$ Films Through a Combination of Ag Nano-Dot Substrate Decoration, Ag/YBCO Quasi-Multilayers, and the Use of BaZrO$_{3}$-Doped Target

摘要

We report on an original technique for nanoengineered pinning centers that combine three previously reported approaches: substrate decoration, quasi-multilayers and targets with secondary phase nanoinclusions. We have used a 4% BZO-doped YBCO target, and Ag nanodots, all grown by PLD. Such an approach gave interesting results in terms of pinning landscape, as proved by TEM studies. Angle-dependent measurements of critical current $I_{rm c}$ showed that, for smaller fields, the absolute maximum in $I_{rm c}$ occur for fields perpendicular to the a-b planes, while at larger fields the absolute maximum in $I_{rm c}$ occurs for fields parallel to the a-b planes, in both cases with a clear second, local maxima. Measurements also showed a smooth change in the character of pinning with magnetic field, from the out-of-plane to in-plane-dominant pinning. For the out-of-plane magnetic field, the highest ${rm I}_{{rm c}{hbox{-}}{rm w}}$ (critical current per cm width) obtained so far, at 77.3 K, occurred in a 5.8 $mu$m Ag nanodots / BZO-doped YBCO trilayer: 782 A/cm-w in self-field, 167 A/cm-w in 1 T and 18 A/cm-w in 3 T.