Magnetoresistance of an insulating amorphous nickel-silicon film in large magnetic fields

High magnetic field measurements for the magnetoresistance ratios R(B,T)/R( 0,T) have been made on an insulating amorphous nickel-silicon thin film. In zero field, the resistance of this insulating film exhibits a "soft gap" v ariable-range hopping law in the liquid helium temperature region. In small fields, negative magnetoresistance values are observed, which can be expla ined using the forward interference (orbital momentum) theory. In intermedi ate and large fields, the magnetoresistance is positive and large and can b e explained using the wave function shrinkage theory. A phenomenological mo del incorporating both processes gives very acceptable fits to the experime ntal data. (C) 2001 Elsevier Science B.V. All rights reserved.