Isotropic and anisotropic pinning in TFA-grown YBa2Cu3O7 −xfilms with BaZrO3nanoparticles

YBCO films grown by the trifluoroacetate (TFA) method with increasing number of BaZrO3 (BZO) nanoparticles have been measured by in-field angular transport measurements to investigate changes in the pinning landscape. The isotropic and anisotropic contributions to the critical current density, Jc(H), with the magnetic field applied in and orientation have been determined, allowing us to characterize the population of isotropic and correlated defects along the c axis and ab planes. First, the influence of the YBCO oxygenation process on the formation of different sorts of anisotropic defects in standard films is demonstrated. Next, we show that the addition of non-coherent BZO nanoparticles to the YBCO matrix produces an expansion of the single-vortex pinning regime toward higher fields, due to the presence of isotropic pinning centers. Moreover, by increasing the amount of isotropic defects in the BZO nanocomposites it is possible to extend the region dominated by strong isotropic pinning centers to large magnetic fields and thus enhance the irreversibility line.