Very-low-temperature electrical resistivity of KRb, KNa, and LiMg alloys.

Abstract

Previous high-precision measurements below 0.5 K showing a resistivity anomaly in KRb and dilute KNa and LiMg alloys have been extended to KNa and LiMg alloy samples which cover the residual-resistivity range from ${\ensuremath{\rho}}_{0}$=4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ to 1.7\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ \ensuremath{\Omega} m. Residual-resistivity data per atomic percent impurity are consistent for all three alloys with literature results in the regions of overlap. The data for all three alloys also show the expected behavior for inelastic electron-impurity scattering. At temperatures above 1 K, the KRb and KNa alloy data show increases in electron-phonon scattering with increasing ${\ensuremath{\rho}}_{0}$ probably due to quenching of phonon drag and---for KRb---to reduction in the Debye temperatures of the alloys. All three alloy systems display a low-temperature anomaly which has a universal magnitude for a given ${\ensuremath{\rho}}_{0}$ when ${\ensuremath{\rho}}_{0}$${<10}^{\mathrm{\ensuremath{-}}7}$ \ensuremath{\Omega} m, and which varies approximately linearly with both temperature and residual resistivity. Localization, electron-electron interaction, and Kondo effects appear to be ruled out as explanations for the anomaly in this regime. Published models based on charge-density waves and ineffectiveness of electron-phonon scattering are also considered. As ${\ensuremath{\rho}}_{0}$ increases above ${10}^{\mathrm{\ensuremath{-}}7}$ \ensuremath{\Omega} m, the anomalous behavior approaches the electron-electron interaction limit. In the very-high-concentration LiMg alloys microscopic differences between the alloys are found to affect the data.