ABSTRACT
The superconducting properties of cuprate superconductors in magnetic fields are closely related to their layered structures (see, for example, Ref. 1). It has been shown experimentally that c-axis-oriented films of high-temperature superconductors such as bismuth cuprates carry large critical current densities at low temperatures, and the current densities stand up to high magnetic fields when the magnetic field is applied parallel to the layers [2-19]. The critical current densities strongly depend on the direction of the magnetic field and show a sharp peak at the field direction parallel to the layers [2-19]. The resistivity above the irreversibility line also strongly depends on the direction of the magnetic field and shows a sudden drop at the direction of the field parallel to the layers [20-25]. These experimental results indicate that the vortices parallel to the layers are prevented from moving perpendicular to the layers. The cuprate superconductors are constructed by alternate stacks of the strongly superconducting Cu02 layers and the weakly superconducting spacing layers. We discuss a role of the layered structure for pinning vortices in cuprate superconductors.
