(Color online) (a) TEM micrographs showing the stacking fault density in type I (low concentration) and type III (high concentration) YBCO tapes. The nanoparticle precipitate density is similar in both types of samples. (b) Field angle dependence of the ab-critical current of YBCO-tapes with high (type III) and low (type I) concentration of stacking faults. The field is always oriented perpendicular to the current. (c) Schematic not-to-scale picture-frame constructions of current flow, projected onto a cross-section of the tape, due to component of the magnetic field that is parallel to the tape direction for the case when the critical current anisotropy is low (top) and when it is larger than the geometrical anisotropy (bottom). These constructions apply to flux densities for which flux-cutting has not occurred yet.
(Color online) (a) Schematic picture of the cross section of the mesa structure. The net applied current flows along c-axis in the Ag/YBCO mesa. (b) Two sets of current-resistance curves at zero external magnetic field and various temperatures. The measurements are performed on samples type I No. 3 and type III No.1 with a same mesa diameter of 150 μm. The large difference in Ic c is induced by the detailed microstructures of these two types of YBCO films.
(Color online) Summary of the temperature dependence of Jc c at self-field. The shaded regions represent the spread of Jc c values for each sample type. It can be clearly seen that the magnitude of Jc c correlates with the stacking fault concentration.
(Color online) (top panel) Temperature dependence of Jc c and of the n-value in self-field of sample type II No. 2. Inset: IV-curves on log-log-scales at 77, 80, 82, 84, 86, and 88 K. (bottom panel) IV-curves for various samples at 77 K and self-field. The n-value is indicated for each curve.
Comparison of critical current density in both c-axis Jc c and ab-plane Jc ab and the out-of-plane critical current anisotropy γ of YBCO films with different pinning microstructures.
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