Angular dependence of the magnetic properties of thin YBa2Cu3O7 − δ films irradiated with Pb and Xe ions

We study the angular dependence of the magnetic properties of Y-ba-Cu-O thin films irradiated with 0.86 GeV Pb and 5 GeV Xe ions. For the Pb irradiated samples the critical current has a maximum when the direction of the external magnetic field coincides with the direction of the columnar defects induced by the irradiation. For the Xe irradiated samples such anisotropy in the critical current was not found. The pinning force density obeys a scaling law of the form b p (1 − b ) q , where b = H ext / H irr ( T ), and H ext and H irr are the external and the irreversibility fields, respectively. The exponents p and q depend on the type and direction of the irradiation.