Upper critical fields of proximity-induced superconducting Cu-Mn matrices in NbTi multifilamentary wires

Abstract

In NbTi multifilamentary wires with Cu-0.5wt% Mn matrices, critical current densities of proximity-induced superconducting matrices J cp were estimated from measured twist-pitch dependence of magnetization. The upper critical field B c2p is obtained by applying the scaling law to J cp data. The value of B c2p at T = 4 is 1.3 T for interfilamentary spacing d N = 0.129 μm and comparable to that of Cu matrix wire with dN = 0.59 μm at T = 4.5 K. The Copper pair penetration length K N − estimated from the temperature dependence of B c2p shows the dirty limit characteristics as T − 1 2 and agrees well with the existing result by ac susceptibility measurement.