Abstract
The density of critical currents jC in Nb thin films with thickness smaller than 15 nm and width between 100 nm and 10 μm has been measured in a wide temperature range. We have found that the temperature dependencies of jC in sub-micrometer wide bridges at 0.7TC < T < TC are well described by the Ginzburg–Landau de-pairing critical current. In wider bridges already at T < 0.9TC the jC value is significantly reduced due to the penetration and de-pinning of magnetic vortices.