Angular Dependence of Critical Current Density in Y-Ba-Cu-O Thin Films

Abstract

c-axis oriented YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin films for coated conductor applications have anisotropic behaviors of critical current density (J/sub c/) in magnetic fields. The anisotropic vortex pinning in YBCO films fabricated on SrTiO/sub 3/(100) single crystal substrates by pulsed laser deposition was investigated based on the field angular dependencies of J/sub c/, which were measured using the constant Lorentz force configuration (CLFC) and a variable Lorentz force configuration (VLFC). J/sub c/(/spl theta/) as a function of angle /spl theta/ between the ab-plane direction and the magnetic field direction had a sharp peak at /spl theta/=0/spl deg/, which was attributed to the intrinsic pinning. Besides, J/sub c/(/spl theta/) did not depend on the intensity of the Lorentz force when the magnetic field was applied near /spl theta/=90/spl deg/. This indicates that J/sub c/(/spl theta/) 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.