Interrelations of atomic structures, electronic structures, electron transport, and magnetic properties across the metal - insulator transition for amorphous alloys

Abstract

The interrelations of the atomic structures, electronic structures, electron transport, and magnetic properties for the amorphous alloy system have been studied over a wide composition range, , with particular attention paid to their changes across the metal - insulator transition. By analysing the temperature dependence of the conductivity, we concluded that the metal - insulator transition occurs in the composition range 15 < x < 20. Structural studies revealed that the V atom is substituted for the Si atom in the tetrahedrally bonded Si network in the range where x < 10, whereas the local atomic structure resembles that of the intermetallic compound in the range 20 < x < 40. These two local structures are apparently competing with each other in the critical composition range 10 < x < 20. Both XPS valence band spectra and electronic specific heat measurements proved that the density of states at the Fermi level is definitely finite even in the insulating regime, i.e., for x < 15. Both V and Si SXS measurements showed that the V 3d states appear just below the Fermi level, and hybridize with the Si 3p states. It is also found that the V atom in the insulating regime possesses a localized magnetic moment, and that the magnetic susceptibility gives rise to a Curie - Weiss-like temperature dependence at low temperatures. Finally, the uniqueness of the electron transport properties for the amorphous alloys is emphasized by the diagram, in which the metal - insulator transition is shown to occur while the density of states at the Fermi level remains finite.