Resistance transitions of thin superconducting films in magnetic fields

Abstract

Resistance transitions of tin films with thicknesses in the range 600 to 10 000 Å have been studied in parallel and perpendicular magnetic fields. The transitions in perpendicular fields are surprisingly sharp, show no sign of a tail at low fields, and are comparatively insensitive to edge effects. The perpendicular field necessary to restore the full normal resistance (H⊥) is never very different from the bulk critical field (Hc) even for films as thin as 600 Å. The sharpness of the transition is apparently due to the persistence of a continuous superconducting thread long after the film has become almost completely normal. Simple theoretical considerations suggest thatH⊥exceedsHconly if the effective penetration depth λЄexceeds the coherence distance