Spin dependent scattering effect in CPP-GMR with current confined path

In this paper, in order to clarify the effect of the spin dependent bulk scattering, comparison of magnetic layer thickness dependence of magnetoresistance (MR) between metal current perpendicular to plane (CPP) and current confined path (CCP)-CPP spin valves is done. The CPP metal spin valve structure is Ta/Ru/PtMn/pinned layer/Cu spacer/free layer/Cu/Ta cap. Three kinds of ferromagnetic materials, Co₉₀Fe₁₀, Fe₅₀Co₅₀ and Fe₅₀Co₅₀ with ultra thin Cu are tried for the pinned and free layers. The CCP-CPP spin valve structure is Ta/Ru/PtMn/Co₉₀Fe₁₀/Ru/pinned layer/NOL spacer/free layer/Cu/Ta cap. The NOL is fabricated by depositing Al₉₀Cu₁₀ and consequently oxidized by using ion-assisted oxidation. In both spin valves, the thickness of the pinned and free layer is changed with maintaining the same thickness. Results show that ΔRA (the product of the resistivity change ΔR and the element size A) increases with increasing film thickness. Also, results reveal that metal CPP needs thicker magnetic film to obtain large MR ratio. At the same RA, it is found out that there is no difference of MR ratio between 3 nm and 4 nm of the pinned and free layers, which indicates the spin dependent bulk scattering is not so effective in the case of CCP-CPP spin valves as in metal CPP spin valves.