Determination of the Critical Current Density in src='/images/tex/19979.gif' alt='hbox {YBa}_{2}hbox {Cu}_{3}hbox {O}_{7-delta }'> Thin Films Measured by the Screening Technique Under Two Criteria

摘要

We report the determination of critical current density J flowing in YBaCuO superconducting thin films by two independent criteria. The estimation of J was carried out by an inductive technique, i.e., the so-called screening technique. Both the imaginary part of the fundamental harmonic of susceptibility χ" and the third harmonic of the voltage V 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. In order to compare the inductive criteria, we investigated the homogeneity of J 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, both techniques yield similar results in the determination of J. However, at temperatures relatively far from T, the V 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 V criterion, avoiding in this way the need for implementing an additional technique.