Resistivity and Magnetoresistance of Dilute Solutions of Cr in Cu-Ni Alloys

The electrical resistivity from 1.3 to 100 K and the longitudinal magnetoresistance from 0 to 85 kOe at 4.2 K were measured on Cu-Ni (Cr) alloys with Ni concentrations of 0, 6, 13, and 23 at.% and Cr concentrations of 0, 125, 300, 600, and 1200 at. ppm. All Cr-bearing samples were observed to exhibit resistivity minima. The difference in resistivity between each Cu-Ni (Cr) alloy and its Cr-free equivalent did not depend linearly on ${log}_{10}T$; the difference in magnetoresistance between these two alloys was found to be negative. The Cr impurity contribution to the resistivity and magnetoresistance showed a marked dependence on the Ni concentration and was proportional to the Cr concentration only in the alloys containing 23 at.% Ni. These results are discussed in terms of spin-flip-scattering processes, characteristic of the Kondo effect, subject to Cr-Cr interactions and the local Ni environment around a Cr cell.