Reducing thickness dependence of critical current density in GdBa2Cu3O7-δ thin films by addition of nanostructured defects

The effect of incorporating nanostructured defects in a form of BaSnO3 (BSO) nanorods on the thickness dependence of critical current density (Jc) in GdBa2Cu3O7-x (GdBCO) thin films was investigated. Pure and 2 wt. % BSO-doped GdBCO films were fabricated by the pulsed laser deposition with the thicknesses t of both films increasing from 0.2 μm to 1.5 μm. The magnetization data measured at 77 K with the field being applied parallel to the c-axis of the films showed two important improvements. First, the Jcs of the GdBCO film were significantly enhanced with the BSO addition. Second, the BSO-doped GdBCO films exhibited less formation of a-axis grains on the film surface than the pure GdBCO films. As a result, a reduced thickness dependence of Jc was obtained for the BSO-doped GdBCO films. The two improvements may be explained by assuming that the growth of BSO nanostructured defects observed in the cross-sectional transmission electron microscopy functioned as effective artificial pinning centers.