Transverse and longitudinal resistivities in NbTi multifilamentary strands with Cu and CuMn matrices

Transverse and longitudinal resistivities have been measured for a pair of multifilamentary strands with filament diameters of 2 mu m, interfilamentary spacing to filament diameter ratio of 0.19, and about 5000 filaments. One of these strands has a Cu matrix and the other has a CuMn matrix. 4.2-K transverse resistivities were extracted from the per cycle eddy current loss and also the magnetization of samples of various twist pitches. Longitudinal resistivities were measured with a four-terminal method at T=12 K. These results are interpreted in terms of size, proximity, and current-path effects. It is found that size effects significantly enhance both the transverse and longitudinal resistivities of the Cu matrix material, and that current-path effects significantly decrease the transverse resistivity of the CuMn material. Additionally, the proximity effect causes the resistivity of the Cu matrix to vary with magnetic field. Resistivity for the Cu matrix at high fields is about 0.6-0.8 that of the CuMn.<>