Strong flux pinning by columnar defects with directionally dependent morphologies in GdBCO-coated conductors irradiated with 80 MeV Xe ions

We show that Xe ion irradiation with 80 MeV to GdBa₂Cu₃O_y-coated conductors creates different morphologies of columnar defects (CDs) depending on the irradiation angles θ _i relative to the c-axis: continuous CDs with a larger diameter are formed for oblique irradiation at θ _i = 45°, whereas the same ion beam at a different angle (θ _i = 0°) induces the formation of discontinuous CDs. The direction-dependent morphologies of CDs significantly affect the angular behavior of the critical current density J _c. In particular, low-energy irradiation defects induce further improvement of J _c in a unique combination of irradiation angles of θ _i = 0° and ±45°: discontinuous CDs at θ _i = 0° and crossed CDs at θ _i = ±45° provide correlated pinning in a wide angular range, which is more strongly enhanced by each other via the pinning of kinks.