Specific Heat and Residual Resistivity of Binary and Ternary Noble-Metal Alloys

Abstract

Electronic specific-heat and residual-resistivity measurements have been made on the ${\mathrm{Ag}}_{\ensuremath{\alpha}}{\mathrm{Au}}_{1\ensuremath{-}\ensuremath{\alpha}}$ binary and the ${\mathrm{Ag}}_{\ensuremath{\alpha}}{(60 \mathrm{at}.% \mathrm{Au}\ensuremath{-}40 \mathrm{at}.% \mathrm{Cu})}_{1\ensuremath{-}\ensuremath{\alpha}}$ ternary disordered alloy systems as well as the two individual samples of ${\mathrm{Ag}}_{0.5}$${(72\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}.%\phantom{\rule{0ex}{0ex}}\mathrm{A}\mathrm{u}\ensuremath{-}28\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}.%\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{u})}_{0.5}$ and ${\mathrm{Ag}}_{0.5}$${(84\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}.%\phantom{\rule{0ex}{0ex}}\mathrm{A}\mathrm{u}\ensuremath{-}16\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{t}.%\phantom{\rule{0ex}{0ex}}\mathrm{C}\mathrm{u})}_{0.5}$. The residual resistances of the binary and ternary systems are found to obey Nordheim's rule only as a first approximation. Specific-heat measurements on the binary system confirm previously published results. Two theories explain the latter either in terms of electron-phonon interactions or electron-impurity interactions. These theories have been extended to a ternary mixture of noble metals, where each predicts a different concentration dependence for the electronic specific heat. The measured results on the ternary alloys are compared with the analytical predictions to distinguish between the two processes involved.