Second-Kind Superconductivity of Indium-Lead Alloys

The magnetization curves of In alloys containing 4.39, 4.75 and 5.57 at.% Pb have been obtained as a function of temperature down to 0.38°K. Three critical fields, H c 2 ( t ), H c 1 ( t ) and H c ( t ), have been determined in the reduced temperature range corresponding to 1> t 2 >0.01. Three kinds of Ginzburg-Landau parameters defined by Maki, κ 1 ( t ), κ 2 ( t ), and κ 3 ( t ), agree well with each other at any temperature. The temperature dependence of κ 1 ( t ) follows qualitatively Maki's prediction, while those of κ 2 ( t ) and κ 3 ( t ) do not. The experimental agreement between κ 1 ( t ) and κ 2 ( t ) can be explained by the recalculation of κ 2 ( t ) by Caroli et al. . The concentration dependence of κ 1 ( t ) is in contrary to theoretical results. By analyzing the results, it was found that alloys with Pb more than 4.1 at.% belong to the second-kind supercon-ductor at any temperature and those with Pb between 3.5 and 4.1 at.% show the transition from first- to second-kind superconductivity at a certain temperature The small residual magnetization tails are discussed on the basis of the surface superconductivity.