Effects of Various Sub-Monolayers on the Properties of Spin Valves with a Co₉₀Fe₁₀ Free Layer

A sub-monolayer of Co₉₀Fe₁₀, Ni₈₀Fe ₂₀, Ta, Cu or Ru was investigated for a spin valve having a Co ₉₀Fe₁₀ free layer. The sub-monolayers of Co ₉₀Fe₁₀, Ni₈₀Fe₂₀, Cu and Ta did not significantly improve the giant magnetoresistance of the spin valve, probably because the spin-dependent scattering due to localized potentials at the Fe impurity in a Co free layer, rather than scattering at the other impurities, dominates the spin valve's magnetoresistance response. As a result of this dominance, the effect of such a sub-monolayer cannot be pronounced, However, since there was some improvement in all but one case, the results clearly confirm that such a layer can play a role as a spin-dependent scatterer. In the case of Ru, the sub-monolayer greatly decreased the giant magnetoresistance value, and this is direct evidence that Ru is indeed a suppressor of bulk spin-dependent scattering.