Evaluation of the out-of-plane coherence length in (103)/(013)YBa2Cu3O7−δ films from electrical transport measurements

Abstract

The out-of-plane plane coherence lengthξc ofYBa2Cu3O7−δ superconductor has been evaluated by analysing the thermallyactivated magnetic vortex flux creep across superconductingCuO2 layers. Currentflow along CuO2 layers has been ensured by patterning (103)/(013) oriented films into severalmacro-bridges positioned at different angles with respect to the crystallineplanes. The bridge in which vortex creep occurs across the intrinsic potential ofCuO2 layers has been selected on the basis of the superconducting transition and current–voltagecharacteristics. Current–voltage characteristics of the selected bridge were analysed in theframework of the theoretical model of Barone et al (1990 J. Supercond. 3 155), which accountsfor a vortex creep in a periodic potential. The estimated out-of-plane coherence lengthξc 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. Theξc value changes in different ways with changing critical temperatureTc, depending on the dominating type of oxygen vacancies and defects.