On the through-thickness critical current density of an YBa ₂Cu ₃O _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 YBa ₂Cu ₃O _7-x thin film containing ∼5 vol % of insulating Y ₂BaCuO ₅ (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/m ³ 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 thefilm thickness.