Determination of the Critical Current Density in Thin Films Measured by the Screening Technique Under Two Criteria

We report the determination of critical current density J_c flowing in YBa₂Cu₃O_7-δ superconducting thin films by two independent criteria. The estimation of J_c was carried out by an inductive technique, i.e., the so-called screening technique. Both the imaginary part of the fundamental harmonic of susceptibility χ₁" and the third harmonic of the voltage V₃ criteria were used to determine the full penetration field. Our goal is to shed light on the selection of the criterion for the determination of J_c. In order to compare the inductive criteria, we investigated the homogeneity of J_c via transport measurements conducted on microbridges patterned in the films. Based on the transport method, we found that, for temperatures close to critical temperature T_c, both techniques yield similar results in the determination of J_c. However, at temperatures relatively far from T_c, the V₃ criterion showed better agreement with the transport data. Furthermore, using both criteria, we propose an alternative methodology to estimate in situ the coil factor associated with the V₃ criterion, avoiding in this way the need for implementing an additional technique.