Determination of Cobalt Spin-Diffusion Length in Co/Cu Multilayered Heterojunction Nanocylinders Based on Valet-Fert Model

Anodized aluminum oxide (AAO) nanochannels of diameter, D, of similar to 50 nm and length, L, of similar to 60 mu m (L/D: approx. 1200 in the aspect ratio), were synthesized and applied as an electrode for the electrochemical growth of Co/Cu multilayered heterojunction nanocylinders. We synthesized numerous Co/Cu multilayered nanocylinders by applying a rectangular pulsed potential deposition method. The Co layer thickness, t(Co), ranged from similar to 8 to 27 nm, and it strongly depended on the pulsed-potential condition for Co layers, E-Co. The Cu layer thickness, t(Cu), was kept at less than 4 nm regardless of E-Co. We applied an electrochemical in situ contact technique to connect a Co/Cu multilayered nanocylinder with a sputter-deposited Au thin layer. Current perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect reached up to similar to 23% in a Co/Cu multilayered nanocylinder with similar to 4760 Co/Cu bilayers (t(Cu): 4 nm and t(Co): 8.6 nm). With a decrease in t(Co), (Delta R/R-p)(-1) was linearly reduced based on the Valet-Fert equation under the condition of t(F) > l(F)(sf) and t(N) < l(N)(sf). The cobalt spin-diffusion length, l(Co)(sf), was estimated to be similar to 12.5 nm.

Automated summary

Anodized aluminum oxide (AAO) nanochannels were synthesized and used as electrodes for the electrochemical growth of Co/Cu multilayered heterojunction nanocylinders. By applying a rectangular pulsed potential deposition method, various Co/Cu multilayered nanocylinders were successfully synthesized. The current perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect reached up to approximately 23% in certain nanocylinders, with the cobalt spin-diffusion length estimated to be around 12.5 nm.