Critical current in wide superconducting films in a weak magnetic field

The critical current I/sub c/ and the magnitude of the slope α = Vertical BardI/sub c//dHVertical Bar (H is a weak perpendicular magnetic field)= have been studied for different reduced temperatures t in polycrystalline films of niobium and niobium nitride, and also in single-crystal niobium films of thickness approx.100 nm and width 100--300 μm. Maxima were found in the curves of α(t) that decreased with increasing external magnetic field (5 Oe< or =H< or =50 Oe) and shifted towards lower temperatures. It is shown that in the region of reduced temperatures t>0.9, for niobium films, and t>0.95 for niobium nitride films, I/sub c/ and α are well described by the Kupriyanov--Likhaev edge pinning mechanism