Vortex creep and critical current densities Jc in a 2 um thick SmBa2Cu3O7-δ coated conductor with mixed pinning centers grown by co-evaporation

Abstract

We report the critical current densities Jc and flux creep rates in a 2 mm thick SmBa2Cu3O7-dcoated conductor produced by co-evaporation. The sample presents strong pinning produced by correlated disorder (boundaries between growth islands, dislocations and twin boundaries) as well as random nanoparticles. Correlated pinning along the c- axis was evidenced due to the appearance of a large peak in the angular critical current, centred at H ║ c. The analysis of the critical current density Jc (with the magnetic field applied parallel (H║c) and at 45° of the c-axis (H║45°)) indicates that correlated disorder assists pinning throughout the temperature range. For all temperatures and at both angles the in-field dependence of Jc exhibits a power-law behavior. The contribution of correlated disorder drops when the field is rotated to intermediate angles between the c axis and a-b axis (i. e. H║45°), which derives in a reduction of the absolute Jc value and poorer in-field dependences. The flux creep rate depends on the angle and its values remain approximately constant within 2 the power-law regime. For H║c and H║45° and for magnetic fields lower than 20 kOe, the flux relaxation presents characterizing glassy exponents u = 1.70 and u =1.32, respectively.