In situ comparison of the critical current density in $Y Ba_2 Cu_3 O_{7-\delta}$ thin films measured by the screening technique under two criteria

摘要

In this investigation we report the determination of the critical currentdensity $J_c$ flowing in a$\mathrm{Y}\mathrm{Ba}_2\mathrm{Cu}_3\mathrm{O}_{7-\delta}$ superconductingthin film. Estimation of $J_c$ was carried out by an inductive technique, theso-called screening technique, in which both the imaginary part of thefundamental harmonic of susceptibility $\chi''_1$ and third harmonic voltage$V_3$ criteria were considered for the determination of the full penetrationfield. In order to verify the reliability of this technique under two criteria,we investigated the homogeneity of $J_c$ via transport measurements conductedon four microbridges patterned in the same film. Based on the transport methodwe found that both techniques yield similar results in the determination of$J_c$ for temperatures close to critical temperature $T_c$. However, attemperatures relatively far from $T_c$, the $V_3$ criterion showed a betteragreement with the transport data. Furthermore, using both criteria, we proposea methodology to estimate in situ the coil factor associated with the $V_3$criterion, avoiding in this way the need of implementing an additionaltechnique.