The dependence of nano-contact magnetoresistance on the bulk scattering spin asymmetry in CoFe alloys with oxidation impurities.
Nano-contact magnetoresistance (NCMR) spin-valves (SVs) using an AlOxnano-oxide-layer (NOL) have numerous nanocontacts in the thin AlOxoxide 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 Co1-xFex. 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 Ωμm2was maximized for Co0.5Fe0.5. To evaluate [Formula: see text] exactly, we fabricated current-perpendicular-to-plane giant magnetoresistance SVs with Co1-xFex/Cu/Co1-xFexlayers 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 Co1-xFexwas also maximized for Co0.5Fe0.5. Additionally, to determine the difference between the experimental MR ratio of NCMR SVs and the theoretical MR ratio, we fabricated Co0.5Fe0.5with oxygen impurities and estimated the decrease in [Formula: see text] with increasing oxygen impurity concentration. Our Co0.5Fe0.5nano-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.
Department of Electronic Engineering, Tohoku University , Aza-Aoba 6-6-05, Aramaki, Aobaku, Sendai 980-8579, Japan.
Yohei
Y
Shiokawa
Department of Electronic Engineering, Tohoku University , Aza-Aoba 6-6-05, Aramaki, Aobaku, Sendai 980-8579, Japan.
JinWon
J
Jung
Department of Electronic Engineering, Tohoku University , Aza-Aoba 6-6-05, Aramaki, Aobaku, Sendai 980-8579, Japan.
Takahiko
T
Otsuka
Department of Electronic Engineering, Tohoku University , Aza-Aoba 6-6-05, Aramaki, Aobaku, Sendai 980-8579, Japan.
Masashi
M
Sahashi