Electronic structure and electron transport properties of amorphous alloys

Abstract

The resistivity at 300 K of the amorphous alloy is only but it increases to when x is increased to 30 in the amorphous alloys. We have studied in this experiment a change in the electronic states immediately below the Fermi level as a function of Ga concentration for amorphous alloys by means of photoemission spectroscopy (XPS and UPS), soft x-ray spectroscopy (SXS) and low temperature specific heat measurements. We reveal that the narrow Mg-Ga bonding states are formed below the Fermi level as a result of the hybridization of Mg-3p and Ga-4p states and that this narrow band gives rise to the pseudogap across the Fermi level. Combining the atomic structure data deduced in the preceding paper, we are led to conclude that the -like short-range order developed with increasing Ga concentration above x = 20 is responsible for causing the narrow p-type bonding states just below the Fermi level and that the simultaneous occurrence of a reduction in the density of states at the Fermi level and an increase in the effective mass results in a sharp increase in resistivity in this system.

Development in the short- and medium-range structure in amorphous alloys

“…Indeed, the formation of the Al-Y and Al-Cu bonding states near the Fermi level has been experimentally confirmed by x-ray photoemission spectroscopy and soft x-ray Al Kβ and Cu Lα 1,2 emission spectroscopy [1]. Moreover, Takeichi et al [2] successfully calculated the atomic structure of the amorphous Al x (Cu 0.4 Y 0.6 ) 100−x (x = 30 and 80) alloys in molecular dynamics simulations by adjusting the parameters involved so as to reconcile the resulting radial distribution function (RDF(r)) with the measured one as closely as possible. By using the atomic structure thus constructed, they further calculated the valence band structure in the linear muffin-tin orbital (LMTO) recursion method and could reproduce well the bonding states near the Fermi level consistent with the observed photoemission spectra.…”