Uniform, graded and spaced arrays of 3 μm triangular antidots in pulsed laser deposited YBa 2 Cu 3 O 7 (YBCO) superconducting thin films are compared by examining the improvements in the critical current density J c they produced. The comparison is made to establish the role of their lithographically defined (non-)uniformity and the effectiveness to control and/or enhance the critical current density. It is found that almost all types of non-uniform arrays, including graded ones enhance J c over the broad applied magnetic field and temperature range due to the modified critical state. Whereas uniform arrays of antidots either reduce or produce no effect on J c compared to the original (asdeposited) thin films.

In order to enhance and/or control critical current density (J c ) in superconducting YBa 2 Cu 3 O 7−δ (YBCO) thin films, different arrays of 3 µm large ferromagnetic (iron) dots with differing configurations and shapes have been deposited on top of high-quality YBCO thin films post-buffered with a layer of CeO 2 . Some tremendous J c enhancement of up to nearly 100% have been obtained at high temperatures and low fields. However, the J c performance is strongly dependent on the array configurations, shape and amount of ferromagnetic iron involved. We show that it is possible to enhance J c at high or low magnetic field ranges. The results are clearly different to similar non magnetic array structures used to previously manipulate J c in YBCO films, which proves the magnetic origin of the changes in J c we observed. The enhancement is likely due to the flux localization and magnetic pinning effects, rather than magnetic shielding alone, which is effective at relatively low fields only. The results also suggest that the observed J c changes depend on rather minor variations in initial pinning and corresponding J c levels of the films. At the same time a common trend for all of the various investigated magnetic arrays could not be established due to explained factors.

Partially (blind) or fully perforated antidots (BADs or ADs, respectively) fabricated by laser lithography and ion beam etching in superconducting YBa 2 Cu 3 O 7 (YBCO) films possess a cumulative circumference wall surface, which is found to be responsible for pinning vortices and/or magnetic flux, whereby increasing the critical current density (J c ) relative to corresponding plain (unpatterned) films. Using a variety of contrastingly shaped, relatively large 2-5 μm BADs and ADs, the J c of YBCO thin films has been effectively increased within the relatively narrow band of wall surfaces of antidots, independent whether patterns are AD or BAD type. Independence of antidot types indicates that enhancement is insensitive whether magnetic flux is inside the ADs, or vortices are inside the BADs. Within this AD wall surface band region a clear shape dependence also emerges. This finding may also provide a guide for superconducting devices requiring maximal J c and reduced associated vortex movement noise.