Anisotropic pinning defects in BaZrO3-doped YBa2Cu3O6+x films in high magnetic fields

Angular dependence of the resistivity, the irreversibility field and the critical current of undoped and BaZrO3-(BZO)-doped YBa(2)Cu(3)O6+x (YBCO) thin films are investigated using pulsed magnetic fields up to 30 T. Doping with BZO forms a dense network of anisotropic c-axis oriented columnar defects, which lead, in comparison with undoped material, to clearly improved values of the pinning potential, the critical current density and the irreversibility field in the whole angular range. The results are explained by point defect scaling theory using a renormalized anisotropy parameter in connection with linear defects. In oblique magnetic field a porous vortex matter is formed by means of kinks on the columnar defects. Our results demonstrate the efficiency of the columnar defects in thin YBCO films in magnetic fields much above the matching field, opening up a possibility to use this material in various high field applications. (c) 2008 Elsevier B.V. All rights reserved.