Artificial pinning in thick YBCO films: Pinning potential and c-axis correlation

We have introduced artificial pinning centres in thick (>1 μm) YBCO films grown by Pulsed Laser Deposition using substrate decoration, quasi-multilayers, and target doping approaches. We have found that the frequency dependence of critical current density is consistent with a logarithmic dependence of pinning potential on current density. For most of materials used as nano-dots, artificially-induced pinning centres have a larger potential than natural ones. From angle-dependent in-field transport measurements and from Transmission Electron Microscopy we have found evidence of c-axis correlated pinning centres.