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 t

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_c showed that, for smaller fields, the absolute maximum in I_c occur for fields perpendicular to the a-b planes, while at larger fields the absolute maximum in I_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 I_c-w (critical current per cm width) obtained so far, at 77.3 K, occurred in a 5.8 μm 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.