Model for the broadening of the resistive transition in thin films

A new analysis of the broadening of the resistive transition under magnetic field in thin films is presented, providing a very good description of the behaviour up to 50% of the normal state resistivity, for fields up to 18 T. We describe films as a collection of clean regions which present a sharp resistivity drop, as observed in clean single crystals and attributed to the vortex lattice melting transition. The structural or chemical inhomogeneities existing in films are modelled by a distributed melting temperature. The field dependence of the distribution width is coherently described by our model. This model, using the classical flux flow theory, yields values for and for the vortex viscosity in close agreement with those currently accepted.