EFFECT OF ELECTRON-ELECTRON SCATTERING ON LOW-TEMPERATURE LORENZ NUMBERS OF DILUTE PD-NI ALLOYS

The thermal and electrical resistivities of Pd-Ni alloys at concentrations ranging from 0 to 1.0 at. Ni have been measured at temperatures between 2 and 20 K. The Lorenz numbers Le appropriate to electron-electron scattering have been extracted from the data and are found to be relatively insensitive to Ni concentration. A theoretical calculation of Le has been carried out under the assumption that the entire current is carried by s electrons which are scattered from spin-density fluctuations of the electrons in the d band. A consistent interpretation of the data is obtained by employing the local-enhancement model, while the uniform-enhancement model is found to yield values of Le which decrease too rapidly with increasing Ni concentration to reasonably represent the experimental results. The calculated value of Le is significantly smaller than the experimental value for pure Pd; it is felt this may be due to the neglect of detailed band-structure effects in this work. Lorenz numbers for Baber scattering have also been calculated by using Coulomb interaction screened by the d electrons. It is found that the presence of Baber scattering cannot remove the discrepancy between theory and experiment for pure Pd. The Baber-scattering model is also used to calculate Le for rhenium and gives very good agreement with experiment. © 1969 The American Physical Society.