Specific Heat of an Icosahedral Superconductor, Mg3Zn3Al2

Abstract

Specific-heat measurements are reported for cubic ($c$), icosahedral ($i$), and amorphous ($a$) phases of ${\mathrm{Mg}}_3$ ${\mathrm{Zn}}_3$ ${\mathrm{Al}}_2$ in the temperature range 0.04-5 K. All three phases are superconducting, with $T_c=0.32, 0.41, \mathrm{and} 0.75$ K, respectively. The electronic density of states $N\left(0\right)\mathrm{}$ is comparable to that expected in the free-electron model for all three phases. Compared to the $c$ phase, significant lattice softening is observed in the $i$ phase and, especially, in the $a$ phase, indicating an increase in the electron-phonon coupling parameter $\lambda$ with decreasing order.