Magnetic Properties of Superconducting Tantalum-Niobium Alloys

概要

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The superconducting properties of Ta-rich Ta-Nb alloys have been investigated by magnetization measurements. The Ginzburg-Landau parameter κ of pure tantalum is estimated to be 0.42 and the critical value κ=1/√<2> is attained at a composition Ta-2.4 at. % Nb. The dependence of the thermodynamic critical field on temperature T follows the BCS prediction and all the alloys are considered to be weak-coupling superconductors. The lower critical field accords with the microscopic theory in the vicinity of the transition temperature T_c, but the discrepancy between experiment and theory increases with decreasing T. The temperature dependence of the upper critical field and the generalized Ginzburg-Landau parameter κ_2 is stronger than the prediction and the disparity becomes large as the electron mean free path l increases. These properties may be ascribed to the effect of the anisotropy of the electronic structure in the state where the electron mean free path l is considerably larger than the intrinsic coherence length ξ_0.
社団法人日本物理学会の論文
1970-11-05