Electrical conductivity around the topological percolation limit in Co–Ag multilayered granular alloys

We calculate the conduction channel contribution to the electrical conductivity of multilayered granular alloys composed of discontinuous Co layers embedded in Ag, alternating with Ag spacers. The electronic transport when the Co clusters percolate is also studied. We focus our attention on the two possible geometries of the conductivity: CIP (current parallel to the Co layers) and CPP (current perpendicular to the layers), and their dependence on cluster size. The electronic structure is self-consistently calculated using a tight binding Hamiltonian, which includes a Hubbard term within the unrestricted Hartree–Fock approximation. On the other hand, the conductivity tensor is obtained by using the semiclassical Boltzmann equation in the relaxation time approximation. We show that the conductivity decreases with increasing cluster size, till percolation is reached, as it is experimentally observed.