The paper presents the results of a study of the electrical properties of a system of nanogranular amorphous Fe-SiO films with a SiO concentration from 0 to 92 Vol.%. For samples with a low SiO content, metallic conductivity takes place. With an increase of the dielectric content, a concentration transition of conduction from the metallic regime to the tunnel regime at a dielectric concentration x 0.6 is observed. At the same concentration, a transition ferromagnet - superparamagnet occurs, which was previously investigated by the magnetic method. For compositions corresponding to the dielectric region, the temperature dependences of the electrical resistance (T) follow the law (T) ~ exp(2(С/kT)1/2), which is typical for the tunnel mechanism of conductivity. Estimation of the sizes of metal granules from the values of the tunneling-activation energy C showed a good agreement with the sizes obtained earlier from the analysis of magnetic properties. In the dielectric range of the compositions, a giant magnetoresistive effect was obtained, reaching 25% at low temperatures.
Caused by the giant magnetoresistive effect changes of microwave refractive index
