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 ${\mathrm{Ag}}_{\alpha }{\mathrm{Au}}_{1-\alpha }$ binary and the ${\mathrm{Ag}}_{\alpha }{(60\mathrm{} \mathrm{at}.\% \mathrm{Au}-40\mathrm{} \mathrm{at}.\% \mathrm{Cu})}_{1-\alpha }$ ternary disordered alloy systems as well as the two individual samples of ${\mathrm{Ag}}_{0.5}$ ${\mathrm{}(72\mathrm{a}\mathrm{t}.\%\mathrm{A}\mathrm{u}-28\mathrm{a}\mathrm{t}.\%\mathrm{C}\mathrm{u})\mathrm{}}_{0.5}$ and ${\mathrm{Ag}}_{0.5}$ ${\mathrm{}(84\mathrm{a}\mathrm{t}.\%\mathrm{A}\mathrm{u}-16\mathrm{a}\mathrm{t}.\%\mathrm{C}\mathrm{u})\mathrm{}}_{0.5}$. 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.