Conduction processes in crystalline Ni_xSi_1-x films

The electrical conductivity and magnetoconductance (MC) have been measured in crystalline nickel-silicon (c-Ni_xSi_1-x) films as a function of nickel content, x. An abrupt decrease in the conductivity is observed at the metal-insulator transition where x_c ≈ 13.5 at.% Ni. The discontinuity is explained in terms of a percolation model. Above 4 K, the magnetoconductance (MC) is negative and arises from an electron-electron interaction contribution and a weak-localization contribution involving strong spin-orbit scattering. Below 4 K, the magnetoconductance rapidly becomes positive. These low-temperature MC data can be explained using a model of electrons scattering from superparamagnetic particles, first introduced by Gittleman et al.