Surface decoration as a prospective artificial pinning strategy in superconducting YBa2Cu3O7x films

This study investigates chemically decorated surfaces as tools for the improvement of transport properties in superconducting YBa2Cu3O7xfilms. This approach, still to be thoroughly investigated, makes use of low-cost easily tunable chemical methods to obtain self-assembled oxide nanostructures on a substrate that will serve, in a second step, for the deposition of the superconducting film itself. The structures are supposed to produce in the superconducting matrix a specific amount of strain, which is generally held responsible for the increased transport capacity of variously doped samples. For the growth of the nanostructures, two different methods have been employed: Polymer-assisted deposition and metal-organic decomposition (MOD). The main advantages and disadvantages of these two routes are discussed. The oxide chosen for the deposition is one commonly used for artificial pinning in YBa2Cu3O7x, namely Ba2YNbO6, together with the less common but highly interesting ferromagnetic compound La0,77Sr0,33MnO3. We also show how the density of these nanostructures can be easily controlled, and the necessary requirements for the growth of nanostructures are determined. A variety of crystalline substrates were tested for the deposition of the nanoparticles, such as SrTiO3, YSZ, MgO. YBa2Cu3O7x films have been deposited on selected samples via standard low-fluorine MOD and characterized scanning electron microscopy (SEM), x-ray diffraction (XRD), vibrating sample magnetometer (VSM), direct current (DC) resistivity, and critical current measurements. The presence of the nanostructures results, in this case, in a slight increased value of Jc, which can be ascribed to the relatively low density of nanoparticles.