Electronic Specific Heats of Alloys of the MgCu2−<i>x</i>Zn<i>x</i> System

Abstract

Specific-heat measurements were made on 17 alloys of the pseudobinary system MgCu2−xZnx between 1.5 and 4.2°K. In addition to the two terminal phases MgCu2 and MgZn2, the compositions studied included nine alloys having the cubic MgCu2 structure, four having the hexagonal MgZn2 structure, and two samples consisting of a mixture of two phases. The density of states at the Fermi level N(EF) was calculated from the measured values of γ. The variation of γ with composition is compared with results from this laboratory previously reported on the MgCu2−xAlx and Mg2−xSix systems. Variation of γ with composition in the cubic range exhibited, qualitatively, the same trends that were shown in the MgCu2−xAlx system, namely, a maximum in γ at 1.44 electrons/atom, a rapid decrease in γ as the stability limit for the cubic phase at ≈ 1.73 electrons/atom is approached, and a shoulder on the falling curve at 1.59 electrons/atom. Values of the Debye θ, calculated from the slopes of the curves of C / T vs T2 are computed for the three systems.