Electromagnetic properties of proximity-induced superconductivity for matrices with different penetration lengths in NbTi multifilamentary wires

Abstract

Interfilamentary proximity coupling behaviour in NbTi multifilamentary wires for ac use with Cu-10 wt% Ni or Cu-30 wt% Ni matrices was investigated quantitatively. Critical current densities of proximity-induced superconducting matrices with filament spacings less than submicron size were estimated from the twist-pitch dependence of the magnetization, and the upper critical fields were evaluated by applying the flux pinning scaling law to the magnetic field dependence of . The obtained values for at 4.2 K were of the order of , depending on the filament spacings, in a low-field region under 1 T and decreased rapidly with increasing applied magnetic field and temperature. Furthermore, the values of Cu-30 wt% Ni matrix were one order smaller than those of Cu-10 wt% Ni matrix with the same filament spacings. The penetration length estimated from the temperature dependence of showed dirty limit characteristics and decreased monotonically as the filament spacing reduced. We also discuss their characteristics in comparison with those of Cu and Cu-0.5 wt% Mn matrices.