Pinning potential in thick PrBa2Cu3Ox/YBa2Cu3O7-δ quasi-multilayers

Using Pulsed Laser Deposition we have fabricated thick quasi-multilayers composed of incomplete layers of PrBa2Cu3Ox (PrBCO) nano-dots and layers of YBa2Cu3O7-delta (YBCO). The number of such sequences was between 2 and 6, with the thickness of individual YBCO layers between 565 and 885 rim, and total thickness between 1.13 and 5.31 mu m. 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) nanodots, both isotropic and c-axis correlated. (C) 2009 Elsevier B.V. All rights reserved.