MOCVD法によるBi系薄膜の超伝導特性

抄録

The critical current density and resistivity of Bi-Sr-Ca-Cu-O films of thickness 5 to 300nm prepared by MOCVD have been investigated. Magnetic Fields up to 6T were applied parallel and perpendicular to the film surface. Zero resistance temperatures (T_c0) for all samples were about 70K. Critical current densities (J_c) for all samples (4.2K, zero applied field) were about 1×10⁶A/cm², but the form of J_c(T) varied with film thickness. This suggested the existence of isolated layers in the film containing different junctions. The films displayed strong anisotropy for magnetic fields applied parallel to, and perpendicular to, the film surface. We suspect this result to originate in the non-penetration of flux quanta (due to the large effective H_c1) and in the potential barrier (surface barrier) to flux penetration at the surface of the thin films in addition to the intrinsic anisotropy of the Bi-based superconductors.