A criterion for the determination of upper critical fields in highly disordered thin-film superconductors.

A procedure is described by which the temperature-dependent upper critical field Hc2(T) in highly disordered thin-film superconductors with broad resistive transitions is determined. Resistance versus perpendicular magnetic field isotherms are used in conjunction with the mean field transition temperature Tc 0, derived from Aslamazov-Larkin fits to the zero-field resistive transition, to determine Hc2(T). The sensitivity of the slope parameter (dHc2/dT)|Tc 0 with respect to the details of the procedure is discussed and the conditions under which meaningful comparisons with theory can be made are elaborated. [ABSTRACT FROM AUTHOR]