Abstract
Nano-contact magnetoresistance (NCMR) spin-valves (SVs) using an AlO (x) nano-oxide-layer (NOL) have numerous nanocontacts in the thin AlO(x) oxide layer. The NCMR theoretically depends on the bulk scattering spin asymmetry ([Formula: see text]) of the ferromagnetic material in the nanocontacts. To determine the relationship between NCMR and [Formula: see text], we investigated the dependence of NCMR on the composition of the ferromagnetic material Co(1-x)Fe(x). The samples were annealed at 270 °C and 380 °C to enhance the MR ratio. For both annealing temperatures, the magnetorsistance ratio in the low-resistance area product region at less than 1 Ω μm(2) was maximized for Co(0.5)Fe(0.5). To evaluate [Formula: see text] exactly, we fabricated current-perpendicular-to-plane giant magnetoresistance SVs with Co(1-x)Fe(x)/Cu/Co(1-x)Fe(x) layers and used Valet and Fert's theory to solve the diffusion equation of the spin accumulation for a ferromagnetic layer/non-ferromagnetic layer of five layers with a finite diffusion length. The evaluated [Formula: see text] for Co(1-x)Fe(x) was also maximized for Co(0.5)Fe(0.5). Additionally, to determine the difference between the experimental MR ratio of NCMR SVs and the theoretical MR ratio, we fabricated Co(0.5)Fe(0.5) with oxygen impurities and estimated the decrease in [Formula: see text] with increasing oxygen impurity concentration. Our Co(0.5)Fe(0.5) nano-contacts fabricated using ion-assisted oxidation may contain oxygen impurities, and the oxygen impurities might cause a decrease in [Formula: see text] and the MR ratio.