X-ray photoelectron spectroscopy study of spin valves with specularly reflective oxide layers

Chemical structures of the specular spin valve with two nano-oxide layers (Ta/Ni₈₀Fe₂₀/Ir₁₉Mn₈₁/Co₉₀Fe₁₀//NOL1//Co₉₀Fe₁₀/Cu/Co₉₀Fe₁₀//NOL2/Ta) were studied by X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there are thermodynamically favorable reactions at the CoFe/NOL1 and NOL2/Ta interfaces. The CoFe sense layer remains metallic, and the Ta capping layer near the CoFe sense layer is oxidized to Ta₂O₅ acting as the NOL2, which is formed through the interface reaction between the oxidized CoFe and the Ta layer. ROLl is a discontinuous oxidation layer because of the existence of some residual metallic CoFe, which allows the direct exchange coupling to exist. Mn atoms of the IrMn layer diffuse into NOL1 during annealing. However, it's further diffusion can be inhibited due to the formation of Mn oxides by the reaction between ROLl and the Mn diffused from IrMn during annealing.