MR enhancement of CPP-GMR by CCP-NOL spacer and Fe/sub 50/Co/sub 50/ magnetic layers

This paper reports that further increase of magnetoresistance (MR) ratio to 6.5/spl sim/8.5% is achieved by using Fe/sub 50/Co/sub 50/ magnetic layers, in addition to current-confined-path(CCP)-nanooxide layer(NOL). The CCP-CPP structure is composed of Ta/Ru/PtMn/Co/sub 90/Fe/sub 10//Ru/pinned layer/NOL spacer/free layer/Cu/Ta cap. Using Fe/sub 50/Co/sub 50//Cu as pinned and free layers, an MR ratio of 6.5/spl sim/8.5% is obtained at area resistance (RA)=300/spl sim/1000 m/spl Omega//spl mu/m/sup 2/ and if Co/sub 90/Fe/sub 10/ is used, MR ratio of 3/spl sim/4% is shown at RA/spl sim/300 m/spl Omega//spl mu/m/sup 2/. The increase of MR ratio is explained by increase of spin dependent scattering at the interface of Fe/sub 50/Co/sub 50/ 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.