Comparison between amorphous and crystalline phases of copper-zirconium alloys by specific-heat measurements

Abstract

The low-temperature specific heat of copper-zirconium alloys in both the amorphous and crystalline states has been measured in the whole concentration range where the amorphous state can be reached by melt spinning. The effects of disorder on the electronic, superconducting, and elastic properties are analyzed in the framework of a simple tight-binding model. In spite of the strong reduction of the electron-phonon interaction associated with disorder, superconductivity occurs in some of the amorphous alloys, but in none of the crystalline ones. In the latter the density of states (DOS) at the Fermi level is markedly affected by the particular characteristics of each compound. This is not the case in the amorphous state where the DOS at the Fermi level varies linearly with concentration. In general, we observe in the amorphous state a 30% reduction of the Debye temperature compared to the crystalline compounds. Such a change is dominated by the shear modulus decreasing and cannot be explained by a mean-field model.