Anisotropic superconducting properties of YBa_{2}Cu_{3}O_{7-δ} (δ=0.1 and 0.4) untwinned single crystals

摘要: We have performed a detailed anisotropy study of the superconducting properties untwinned single crystals ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ for \ensuremath{\delta}\ensuremath{\approxeq}0.1 and \ensuremath{\delta}\ensuremath{\approxeq}0.4 in magnetic fields up to 22 T using rf method giving critical ${\mathrm{H}}^{\mathrm{*}}$ which are determined by onset flux-line motion. For we find highest along b axis; a-b amounts 20% at 85 K. The 60-K superconductivity is characterized largest axis pronounced 2D behavior as manifested cusp angular dependence extremely steep slope ${\mathrm{H}}^{\mathrm{*}}$(T) perpendicular c. discuss our experimental results with respect significance Cu-O chains high-${\mathrm{T}}_{\mathrm{c}}$ ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$.