Angular Behavior of J_c in GdBCO-Coated Conductors with Crossed Columnar Defects Around ab Plane

We investigated in detail the flux pinning properties around B || ab for GdBCO-coated conductors with crossed columnar defects produced by heavy-ion irradiation, where the crossing angle Θ_i was systematically controlled in the range from ±5° to ±15° relative to the ab plane. A single peak of critical current density J_c centered at B || ab occurs for the crossing angle of Θ _i = ±5°, where an upward shift in J_c can be observed compared to an unirradiated sample. As the crossing angle is larger, the J_c peak becomes smaller and broader while maintaining the peak at B || ab. Increasing Θ_i up to ±15°, three J_c peaks emerges at B || ab and at the two irradiation angles, independently from the others. The crossover behavior from the single peak to the triple one around the ab plane is attributed to the strong line tension energy of flux lines around B || ab , which derives from the elliptical nature of the core of flux lines in anisotropic superconductors.