Specific Heat of Gold-Zinc Alloys below 3 °K

The electronic specific heat is found to initially increase on adding zinc to gold, in agreement with recent work of Clune and Green who relate this behavior to changes in the electron-phonon enhancement factor superimposed on a rigid-band model. The results for a 7.5-at.%-Zn alloy were stable against drastic changes in heat treatment, whereas those for a 10-at.% alloy were very dependent on heat treatment. It is therefore postulated that the $\alpha$-phase region extends only to ∼ 9 at.% at room temperature, contrary to recent phase diagrams. The results at 10 at.% Zn also suggest that very slow cooling retains a large part of the $\alpha$ phase, but quenching produces the ordered phase. A possible explanation is that the high lattice-vacancy concentration immediately after quenching facilitates atomic movement.