Supercurrent transport in Y Ba 2 Cu 3 O 7 − δ epitaxial thin films in a dc magnetic field

摘要: Magnetic field and angle dependences of the critical current density ${J}_{c}(H,\ensuremath{\theta})$ in epitaxial $c$-oriented $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ thin films are measured by four-probe transport technique, low-frequency ac magnetic susceptibility, superconducting quantum interference device magnetometry. The under study deposited off-axis dc magnetron sputtering onto $r$-cut sapphire substrates buffered with a $\mathrm{Ce}{\mathrm{O}}_{2}$ layer. A consistent model vortex pining supercurrent limitation is developed discussed. Rows growth-induced out-of-plane edge dislocations forming low-angle boundaries (LAB's) shown to play key role achievement highest ${J}_{c}\ensuremath{\geqslant}2\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.3em}{0ex}}\mathrm{A}∕{\mathrm{cm}}^{2}$ at $77\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. takes into account transparency LAB's for as well pinning lattice on network LAB's. Principal statistical parameters film defect structure, such domain size distribution mean misorientation angle, extracted from ${J}_{c}(H)$ curves $H$ applied parallel $c$ axis x-ray diffraction data. An evolution ${J}_{c}(\ensuremath{\theta})$ be supposing dominant dislocations. Strongly pinned vortices appear exist tilted low fields up characteristic threshold field, below which induction within obeys simple relation $B=H\phantom{\rule{0.2em}{0ex}}\mathrm{cos}\phantom{\rule{0.2em}{0ex}}\ensuremath{\theta}$. This feature explain absence expected maximum $H\ensuremath{\parallel}c$ field. peak an angular hysteresis ${J}_{c}(\ensuremath{\theta})$, have been observed intermediate-field range, discussed terms thickness, surface quality, orientation effects found model.