Second-Kind Superconductivity of Indium-Lead Alloys

概要

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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_<c2>(t), H_<c1>(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), andκ_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 superconductor 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.
東北大学の論文