Strong, asymmetric flux pinning by miscut-growth-initiated columnar defects in epitaxial YBa2Cu3O7-x films.

Abstract

Strong flux pinning and a pronounced asymmetric angular dependence of ${J}_{c}(H,\ensuremath{\theta})$ have been discovered in ${{\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}\mathrm{O}}_{7\ensuremath{-}x}$ films grown on miscut, mosaic LaAl${\mathrm{O}}_{3}$ substrate surfaces. A new pinning peak, which at low fields is nearly as strong as the ``intrinsic pinning,'' is observed for magnetic field orientations between the $c$ axis and the Cu${\mathrm{O}}_{2}$ plane. Cross-section transmission electron microscopy reveals columnar growth defects (2--3 nm diameter) aligned near the $c$ axis, in concentrations $\ensuremath{\sim}{10}^{10}{\mathrm{cm}}^{\ensuremath{-}2}$. The results demonstrate that deliberately modified substrate surfaces may introduce technologically useful flux pinning in ${{\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}\mathrm{O}}_{7\ensuremath{-}x}$ films.