Comparison of transport and magnetization critical currents in c-axis-oriented Y₁Ba₂Cu₃O_7-δ thin films

Transport, structural, and magnetic properties of c-axis-oriented Y ₁Ba₂Cu₃O_7-δ thin films grown by off-axis in situ rf sputtering on MgO substrates have been investigated. By varying the substrate surface preparation prior to deposition, films could be grown with systematic improvements in their dc transport and structural properties. At the same time, these films display a systematic decrease in the irreversible magnetization ΔM(H) at all temperatures. Transport and inductive critical current densities in all cases displayed a temperature dependence that could be ascribed to flux creep and/or intragrain Josephson junctions. The irreversible magnetization for the films showed sample size dependence consistent with that of the Bean critical-state model. An anticorrelation between the transport and the magnetization critical current densities in the films was observed, which can be understood in terms of changes in the density of pinning sites as a function of substrate preparation.