Deviations from Matthiessen's rule and longitudinal magnetoresistance in copper

TLDR: In this paper, anomalous phonons were measured as a function of temperature between 4°K and 300°C, and it was shown that the influence of the defects on the temperature-dependent part of the electrical resistivity plays an important role mainly at low temperatures.

Abstract: Deviations from Matthiessen's rule (MR) due to phonons inCuAu andCuNi alloys were measured as a function of temperature between 4°K and 300°C. They can amount to 40% of the residual resistivity of the doped samples. A second group of measurements concerns deviations from MR that occur inCuNi during a neutron irradiation at 4.6°K. It turned out that there are two essential reasons for these deviations. The first one is the influence of the defects on the temperature-dependent part of the electrical resistivity. It plays an important role mainly at low temperatures. We found experimentally and theoretically aT5 dependence for this additional resistivity at low temperatures. The second reason is the existence of anisotropies in the Fermi surface of Cu and in the scattering potential of the defects. These deviations can be described, as suggested by J. M. Ziman, by a two-band model for the Fermi surface. Furthermore, we could show that the enhanced resistivity increase in theCuNi alloys during neutron irradiation at 4.6°K, which was generally interpreted as an enhanced defect production, is essentially caused by deviations from MR. Measurements of the longitudinal magnetoresistance of the doped copper at 4.2°K were very useful for discriminating between the different causes of deviations from MR.