Size and proximity effects in multifilamentary superconducting wires

• Published in: Cryogenics (Guildford) 1986-03, Vol.26 (3), p.152-156
• Main Authors: Lazar, D.P., Vladimirova, N.M., Drobin, V.M., Dyachkov, E.I., Khukhareva, I.S.
• Format: Article
• Language: English
• Subjects: Applied sciences; Electrical engineering. Electrical power engineering; Exact sciences and technology; Materials; multifilamentary wires; superconductors
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/0011-2275(86)90213-4

The longitudinal resistance of a copper matrix in commercial multifilamentary superconducting wires with various numbers and diameters of Nb-Ti filaments has been measured. This was done at a temperature, T ≈ 12 K when P Nb&z.sbnd;Ti , ≈10 3 P cu so that the longitudinal resistance of a sample is entirely determined by copper. For all samples the resistivity, ϱ ∥, in the core consisting of both Cu and NbTi, is greater than the resistivity, P cu, in the surface superconductor-free layer. Size effect makes a significant contribution to the value of ϱ ∥. If a current is passed through a multifilamentary superconducting wire perpendicular to the superconducting filaments, a state specific to two-dimensional superconductors is created. The temperature dependence of the transverse resistance of the samples used was analogous to that of the resistance of a two-dimensional system. Thus, after the superconducting transition of the NbTi-50 filaments, a decrease in the temperature leads to a monotonic decrease of the resistance due to the proximity effect. This is in good agreement with a mathematical model developed for such two-dimensional superconductors.