Anisotropy of the critical current in YBCO thin films grown by metal organic chemical vapour deposition

A study of the anisotropy of the critical current in YBCO films is reported. The films have been grown on LaAlO3 substrates by metal organic chemical vapour deposition. Current-voltage (I-V) measurements have been performed on microbridges using a single pulsed method. The angular magnetic field dependence of the critical current density Jc(θ) has been measured for temperatures close to Tc and down to 40 K. Films having different fraction of a-axis grains are compared. Significant differences that may be attributed to the differences in microstructure are stressed out. In particular films with a larger amount of a-axis grains exhibit an enhanced pinning when H is parallel to the substrate normal, indicating a flux pinning mechanism that is directionally oriented. (orig.)