On the through-thickness critical current density of an YBa₂Cu₃O_7-x film containing a high density of insulating, vortex-pinning nanoprecipitates

Using sequential ion milling the authors have studied the thickness dependence of the critical current density J_c(H) of a single crystal 1 μm thick YBa₂Cu₃O_7-x thin film containing ∼5 vol % of insulating Y₂BaCuO₅ (Y211) nanoparticles in order to better understand how to obtain high critical currents in thick films. Except very near the interface where the defect density was enhanced, J_c(H) in the body of the film was uniform and independent of thickness with a high maximum pinning force of 8.8 GN/m³ at 77 K. The authors conclude that the nanoscale Y211 precipitates result in strong, three-dimensional pinning characterized by a pin spacing of ∼30 nm, much smaller than the film thickness.