Influence of growth temperature on critical current and magnetic flux pinning structures in y Ba2 Cu3 O7-x

We have studied the critical current density (Jc) as a function of applied magnetic field (H) magnitude and orientation for ∼1-μm -thick Y Ba2 Cu3 O7-x films grown by pulsed laser deposition at growth temperatures (Tg) from 730 to 870 °C. With changing Tg, alternately a high density of planar defects (Y Ba2 Cu4 Ox intergrowths) or columnar defects (Y-Cu-O nanocolumns) are introduced. These defects produce a maximum for Jc (H∼1 T) parallel to the plane of the film or the film normal, respectively. For Tg 830 °C, we present evidence of a Ba-Cu-O liquid phase during growth, which results in a dramatic change in both the microstructure of the films and magnetic field orientation dependence of Jc.