Critical Fields in Layered Superconducting Systems

Layered systems are considered which behave as single, but anisotropic superconductors. Supposing a second order transition in the presence of an external field, the critical fields H c2 and H c3 in the GL region are calculated. H c2 is a function of the angle θ between the magnetic field and the direction perpendicular to the layers; H c3 depends on θ in the same way as H c2 , the ratio H c3 / H c2 being the same as in the isotropic case ( H c3 / H c2 = 1.69). In the limiting case of thin layers it is found that H c2 is independent of the period of the layered structure, and is larger in the parallel (θ: π/2) then in the perpendicular (θ = 0) case.