Investigations of interface spin asymmetry and interfacial resistance in Fe_xCo_100-x/Ag interface

We investigated current-perpendicular-to-plane (CPP) magnetotransport parameters of Fe_xCo_100-x/Ag interfaces: interface specific resistance (AR_F/N), extended interface resistance (AR^∗_F/N), and spin scattering asymmetry (γ). We also investigated the dependence of interfacial parameters on the giant magnetoresistance effect with CPP geometry. For measuring these parameters, we prepared magnetic multilayers and pseudo spin valves (PSVs), combining the ferromagnetic (F) alloys Fe, Co, Fe₅₀Co₅₀, and Fe₃₀Co₇₀ with the nonmagnetic (N) metal Ag. In all cases, the largest AR_F/N value was found to be ∼0.68 mΩ μm² with an enhanced AR^∗_F/N value of ∼1.9 mΩ μm² for a (001)-oriented Fe/Ag interface, which suggests that spin-up and spin-down electrons on the Fermi surface have very different transmission probabilities. Such an interface can act as a spin filter through which only one type of electrons can pass.