Evaluation of the out-of-plane coherence length in (103)/(013) YBa ₂Cu₃O_7-δ films from electrical transport measurements

The out-of-plane plane coherence length ξ_c of YBa ₂Cu₃O_7-δ superconductor has been evaluated by analysing the thermally activated magnetic vortex flux creep across superconducting CuO₂ layers. Current flow along CuO₂ layers has been ensured by patterning (103)/(013) oriented films into several macro-bridges positioned at different angles with respect to the crystalline planes. The bridge in which vortex creep occurs across the intrinsic potential of CuO₂ layers has been selected on the basis of the superconducting transition and current-voltage characteristics. Current-voltage characteristics of the selected bridge were analysed in the framework of the theoretical model of Barone et al (1990 J. Supercond. 3 155), which accounts for a vortex creep in a periodic potential. The estimated out-of-plane coherence length ξ_c ranges between 0.11 and 0.30 nm for films with different oxygen and structural defect contents, consistently with values evaluated with different techniques and reported in the literature. The ξ_c value changes in different ways with changing critical temperature T_c, depending on the dominating type of oxygen vacancies and defects.