Isotropic enhancement in the critical current density of YBCO thin films incorporating nanoscale Y₂BaCuO₅ inclusions

The effect of incorporation of nanoscale Y₂BaCuO₅ (Y211) inclusions on the vortex pinning properties of YBa₂Cu₃O_7-δ (YBCO or Y123) superconducting thin films is investigated in detail on the basis of variation of critical current density (J_C) with applied magnetic field and also with the orientation of the applied magnetic field at two different temperatures: 77 K and 65 K. Surface modified target approach is employed to incorporate nanoscale Y211 inclusions into the superconducting YBCO matrix. The efficiency of Y211 nanoinclusions in reducing the angular anisotropy of critical current density is found to be significant. The observed angular dependence of the critical current density is discussed on the basis of mutually occupied volume by a vortex and spherical and/or planar defect. A dip in J_C near the ab-plane is also observed which has been analyzed on the basis of variation of pinning potential corresponding to a spherical (3-D) or planar (2-D) pinning center and has been attributed to a reduced interaction volume of the vortices with a pinning center and competing nature of the potentials due to spherical and planar defects.