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

The electrical resistivity from 2 to 100 K and the longitudinal magnetoresistance from 0 to 85 kOe at 4.2 K have been measured on Cu_1-xNiₓ alloys ($x=0.06, 0.12, 0.23$) containing 0 to 1175 ppm Mn as magnetic impurities. All Mn-bearing samples exhibited resistivity minima, and the difference in resistivity between each Cu_1-xNiₓ(Mn) alloy and its Mn-free equivalent depended linearly on log₁₀T for nearly an order of magnitude in T. These phenomena are characteristic of dilute magnetic alloys and suggest that the results can be interpreted in terms of the Kondo effect. This picture is supported by the magnetoresistance of the alloys, which was negative for all Mn-bearing samples. The magnetic contributions to the resistivity and magnetoresistance were also proportional to the Mn concentration and essentially independent of Ni concentration. The former result is interpreted as an indication that interaction effects among the Mn ions were negligible, and the latter result suggests that the Ni had very little effect on the local-moment character of the Mn.