Insulting amorphous Ti x Si 100Ϫx (xϽ9.5) alloys are characterized by the Mott-type variable-range hopping ͑VRH͒ conduction and a finite electronic specific heat coefficient ␥ at low temperatures. We use magnetoresistance data to deduce the localization radius and the density of electronic states N 0 responsible for the dc transport in the system. The value of N 0 thus obtained was found to be two orders of magnitude less than the specific heat density of states defined as g 0 ϭ3␥/ 2 k B 2 . We conclude that, in insulating amorphous Ti x Si 100Ϫx

Magnetic properties have been measured in magnetic fields up to 70 kOe over the temperature range 1.8-300 K for a series of amorphous TixSi100-x (3⩽x⩽41) alloys and two amorphous VxSi100-x (x = 7 and x = 12) alloys. We found that the magnetic properties of amorphous TixSi100-x alloys change gradually as the Ti concentration varies across the metal-insulator transition (x = 9.5). The alloys are non-magnetic at high Ti content (x>25), whereas the insulating alloys and even metallic ones near the metal-insulator transition exhibit a divergent magnetic susceptibility consistent with the formation of localized magnetic moments. At temperatures below 50 K, the susceptibility of these magnetic alloys follows the Curie-Weiss law well, with very small values of the Curie temperature. The fitting of the low-temperature magnetization data for the amorphous TixSi100-x and VxSi100-x alloys revealed that the magnetic moments are characterized by the spin value of 1/2 and a g-factor equal to 2. The room temperature electron spin-resonance measurements identified these moments as arising from the dangling bonds inherent to the network of amorphous Si and ruled out the possibility of the alloys having the d-state magnetism associated with Ti and/or V atoms.

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