Specific heats of α-phase Cu-Al and dilute magnetic Cu-Al (Fe) alloys

The specific heats of a series of α-phase Cu-Al and dilute magnetic Cu-Al (Fe) alloys with iron concentrations near 0.07 at.% have been measured over the temperature range 1-14 K. The alloys had aluminum concentrations of 0, 2.5, 5, and 10 at.%. The electronic specific-heat coefficient and the Debye temperature were determined for the iron-free samples. Both were found to increase with increasing aluminum concentration. The increase in the electronic coefficient can be related to shielding effects, and the change in the Debye temperature is consistent with the mass defect associated with an aluminum atom. The excess specific heat due to the iron impurities showed the broad peak characteristic of the Kondo effect. The temperature of the maximum was essentially independent of aluminum concentration, while the size of the peak decreased with aluminum additions. This behavior is contrasted with the behavior of similar dilute magnetic alloys.