Heat Capacity of Pseudo-Copper below 4.2°K

Abstract

Heat-capacity measurements have been made on two face-centered-cubic alloys of the type ${\mathrm{Cu}}_{1\ensuremath{-}2x}{\mathrm{Zn}}_{x}{\mathrm{Ni}}_{x}$ at temperatures below 4.2\ifmmode^\circ\else\textdegree\fi{}K for the values $x\ensuremath{\approx}0.03$ and $x\ensuremath{\approx}0.08$. The heat capacity has been found to obey a law of the type ${C}_{v}=\ensuremath{\gamma}T+(\frac{464.5}{{{\ensuremath{\theta}}_{D}}^{3}}){T}^{3}$ cal/mole (\ifmmode^\circ\else\textdegree\fi{}K). The Debye characteristic temperature ${\ensuremath{\theta}}_{D}$ is nearly the same as that for pure copper. For an alloy having $x\ensuremath{\approx}0.03$, ${\ensuremath{\theta}}_{D}$ is approximately 1% higher than ${\ensuremath{\theta}}_{D}$ for pure copper. However, $\ensuremath{\gamma}$ increases rapidly with increasing $x$, and is approximately 20% higher than the $\ensuremath{\gamma}$ for pure copper when $x\ensuremath{\approx}0.03$. The results are found to be incompatible with a rigid-band model approach to alloy theory.