Pinning potential in thick PrBa 2Cu 3O x/YBa 2Cu 3O 7−δ quasi-multilayers

Abstract

Using Pulsed Laser Deposition we have fabricated thick quasi-multilayers composed of incomplete layers of PrBa 2Cu 3O x (PrBCO) nano-dots and layers of YBa 2Cu 3O 7− δ (YBCO). The number of such sequences was between 2 and 6, with the thickness of individual YBCO layers between 565 and 885 nm, and total thickness between 1.13 and 5.31 μm. For the thinner quasi-multilayer, DC magnetization studies showed an increase in the critical current density J c at all fields in comparison with a pure YBCO reference sample, while the thicker samples showed an increased J c only in high fields. We have also investigated the frequency dependence of J c from AC susceptibility studies and found that the pinning potential is well described by a logarithmic dependence on current density. Pinning potentials in PrBCO/YBCO quasi-multilayers also proved to be higher than in the reference sample at high fields. From angle-dependent transport measurements we have found indications of strong pinning centres induced by the (PrBCO) nano-dots, both isotropic and c-axis correlated.