Abstract :
We have measured the electrical resistance and magnetoresistance near the metal–insulator transition in films of the amorphous alloys GdxSi1−x and YxSi1−x (x∼0.14 – 0.15) for 0.1 K<T<20 K in an applied magnetic field 0 kOe<H<105 kOe. In a low magnetic field, a-GdxSi1−x is an insulator and the conductivity approximately follows the expected behavior for variable range hopping. With increasing field H the conductivity of a-GdxSi1−x increases by ∼3 orders of magnitude at low T, crosses through an insulator to metal transition and approaches the conductivity of a-YxSi1−x indicating that the effect of the magnetic Gd impurities on transport is dimished by the application of a magnetic field. The low-temperature conductivity on the metallic side of the transition scales approximately linearly with the applied magnetic field, indicating that the critical exponent μ≈1.
