Electronic structure and electron transport properties of AlCuY and MgCuY amorphous alloys

Abstract

The effect of Al and Mg on the electronics tructure and electron transport properties of late transition metal-early transition metal type amorphous alloys has been clarified by analysing the data on amorphous Al x (Cu 0.4Y 0.6) 100− x and Mg x (Cu 0.4Y 0.6) 100− x alloys. No sizeable chemical bonding effect is observed when Mg is introduced into the amorphous CuY matrix. This explains the observed monotonic decrease in resistivity and electronic specific heat coefficient and the persistance of a negative Hall coefficient over the whole Mg concentration range. In contrast, the electronic structure changes drastically when Al is introduced into it. A combination of the X-ray photoemission spectroscopy and soft X-ray emission spectroscopy spectra led us to conclude that strong chemical bonding between Al and transition metals Y and Cu is formed and that this eventually results in the free-electron-like band structure in the Al-rich region. The formation of AlY and AlCu covalent bonding and the resulting depletion of the Al 3p and Y 4d electrons at the Fermi level explains an increase in resistivity coupled with a sharp decrease in the electronic specific heat coefficient and also, possibly, the occurrence of a positive Hall coefficient in the amorphous AlCuY alloys.