Temperature dependence of the critical current and pinning behaviour in superfine filamentary NbTi wires

Abstract

Field dependence of critical current density Jc and its temperature dependence in superfine filamentary NbTi wires were measured to investigate the effect of filament diameter df on Jc. Samples which are in the df range of 0.061-1.53 mu m have CuNi matrix or Cu-CuNi mixed matrix. Field dependences of Jc at 4.2 K are very different among samples with different values of df. As df is decreased, Jc values at 2 T reach a maximum, 1*106 A/cm2, around df=0.072 mu m. In high fields, the Jc of these samples depends on df and lower Jc values are obtained in samples with finer filaments. As the sample temperature rises, the Jc is highly reduced, especially, for finer filamentary samples.