Magnetoresistance in magnetic multilayers: A role of Fermi velocity

Transport properties of a magnetic metallic multilayer system Co/Cu are investigated based on first-principles band-structure calculations in order to explore the microscopic origin of the giant magnetoresistance (MR) observed. We especially focus on the dependence of the Fermi velocity on the magnetic configuration of the magnetic Co layers. It is found that the dependence possibly explains a certain amount of the giant MR. The alloying effect of the magnetic layers on the MR is also studied and the result is qualitatively consistent with recent experiments. The change in the Fermi velocity of the up-spin channel dominates a trend in the alloying effect. A further analysis of the Fermi velocity using a simple tight-binding model is also presented.