MR enhancement of CPP-GMR by CCP-NOL spacer and Fe50Co50 magnetic layers

This paper reports that further increase of magnetoresistance (MR) ratio to 6.5∼8.5% is achieved by using Fe₅₀Co₅₀ magnetic layers, in addition to current-confined-path(CCP)-nanooxide layer(NOL). The CCP-CPP structure is composed of Ta/Ru/PtMn/Co₉₀Fe₁₀/Ru/pinned layer/NOL spacer/free layer/Cu/Ta cap. Using Fe₅₀Co₅₀/Cu as pinned and free layers, an MR ratio of 6.5∼8.5% is obtained at area resistance (RA)=300∼1000 mΩμm² and if Co₉₀Fe₁₀ is used, MR ratio of 3∼4% is shown at RA∼300 mΩμm². The increase of MR ratio is explained by increase of spin dependent scattering at the interface of Fe₅₀Co₅₀ and Cu metal path where current is concentrated. Conduction examination shows that there is a resistance increased caused by joule heating effect with increasing voltage, indicating that great majority of current flows in metal paths. The origin of MR comes from nano-constricted metal path regions which dimension is less than the mean free path of electron.