Electronic properties of Mg-based simple metallic glasses

Abstract

Measurements of the Hall coefficient, the low-temperature specific heat and the electrical resistivity are reported for a large number of Mg-based metallic glasses of the type Mg0.7Zn0.3-xXx (X=Cu, In and Sn) and Mg-Ga-Al. The Hall coefficient is negative and independent of temperature. The effective electron concentration, deduced from the Hall coefficient, turns out to be always lower than the corresponding nominal value and to be a common feature of all Mg-based metallic glasses studied. Nevertheless, the electronic specific heat coefficient can be described approximately by the free-electron model with the effective electron concentration. Concerning the electronic transport properties, all Mg-based metallic glasses are characterised by a negative TCR at high temperatures (150-300K) and with a value of rho 300K ranging from 50 to 110 mu Omega cm. The temperature corresponding to the resistivity maximum, Tmax, decreases almost linearly with increasing rho 300K and disappears at about 90 mu Omega cm. All these features can be interpreted in terms of the generalised Faber-Ziman model with the saturation effect incorporated. Superconductivity is observed in the metallic glass Mg46Ga36Al18 with a transition temperature Tc=1.90K.