Angular dependence of critical current density in Y-Ba-Cu-O thin films

c-axis oriented YBa₂Cu₃O_7-δ (YBCO) thin films for coated conductor applications have anisotropic behaviors of critical current density (J_c) in magnetic fields. The anisotropic vortex pinning in YBCO films fabricated on SrTiO₃(100) single crystal substrates by pulsed laser deposition was investigated based on the field angular dependencies of J_c, which were measured using the constant Lorentz force configuration (CLFC) and a variable Lorentz force configuration (VLFC). J_c(θ) as a function of angle θ between the ab-plane direction and the magnetic field direction had a sharp peak at θ=0°, which was attributed to the intrinsic pinning. Besides, J_c(θ) did not depend on the intensity of the Lorentz force when the magnetic field was applied near θ=90°. This indicates that J_c(θ) in this region is determined by the depinning of the vortex segment trapped by the pinning centers parallel to c-axis of the film. A transition from the intrinsic pinning to the extrinsic pinning is also discussed.