Surface Decoration as a Prospective Artificial Pinning Strategy in Superconducting YBa2Cu 3O${}_{7\text{-}\text{x}}$ Films

This study investigates chemically decorated surfaces as tools for the improvement of transport properties in superconducting YBa ₂ Cu ₃ O _7-x films. 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 YBa ₂ Cu ₃ O _7-x , namely Ba ₂ YNbO ₆ , together with the less common but highly interesting ferromagnetic compound La _0,77 Sr _0,33 MnO ₃ . 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 SrTiO ₃ , YSZ, MgO. YBa ₂ Cu ₃ O _7-x 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 J _c , which can be ascribed to the relatively low density of nanoparticles.