Flux pinning properties in YBa2Cu3O7−δ multilayered films with second phases prepared by PLD method

We present the experimental studies on structures and superconducting properties of two different types of YBa2Cu3O7−δ multilayered films with second phases prepared by pulsed laser deposition. As second phase materials, Y2O3 and ZnO were inserted into films, respectively. The nano-particles were observed on a YBa2Cu3O7−δ layer when several pulses for second phase materials target ablation were chosen for both Y2O3 and ZnO. The critical temperatures of almost multilayered films were slightly reduced as compared to that of the pure YBa2Cu3O7−δ film, while the superconductivity was destroyed in the case of excess doping of ZnO. For half-multilayered films which consist of a lower layer with multilayer and an upper one with mono-YBa2Cu3O7−δ, the most improved critical current densities were observed in both cases of Y2O3 and ZnO inclusions. This result indicates that there is a hope of further enhancement of critical current density by choosing the optimum in variety of spatial distributions of nano-particles, in addition to optimizing the dope level.