Direct observation of the flux line lattice in Al-doped YBa2Cu3O7−δ

摘要: Abstract The high-resolution Bitter pattern technique has been used to study the flux line lattice (FLL) in Al-doped YBa 2 Cu 3 O 7−δ (YBCO) single crystals with 4% of atoms substituted for Al. In contrast undoped YBCO, FLL was isotropic and no effects vortex interaction twin boundaries were found which is consistent extremely small size domains ≈30 A these brought about by Al-doping. addition, consisted misoriented inside an undisturbed regular arrangement seen, whose dimensions rapidly increased magnetic field. This behaviour testifies being collectively pinned weak pinning sites such as vacancies, defect clusters, etc. Proceeding from domains, we estimated critical current density our be j c ≈3 x 10 A/ cm , two orders magnitude lower than typical value YBCO crystals, but same order Fe-doped YBCO.