Thickness Dependence ofκ2and Related Problems for Superconducting Alloy Films in Strong Fields

Abstract

Using the tunneling technique, we have studied superconducting alloy films of InBi in strong magnetic fields parallel and perpendicular to the surface. Measurements in perpendicular geometry confirm previous results for bulk type-II samples. Additionally they show the decreased effect of screening currents for thin films predicted by Maki. In parallel geometry we find the parameter ${\kappa }_2$ (related to the slope of the magnetization in high field) to be a function of film thickness. Anomalies observed from tunneling characteristics which we associated with the entry of flux quanta in the film are studied in detail. We construct a general diagram showing the film behavior near the nucleation field as a function of thickness and Ginzburg-Landau parameter $\kappa$.