Reduction in critical current density by tuning damping constants of CoFeB for spin-torque-transfer switching

Different capping layers were deposited on 2.5 nm Co₇₂Fe₈B₂₀ to investigate their effects on damping constants and critical current density (J_C0) for spin-torque-transfer switching. The damping constant of CoFeB is affected by the interfacial conditions and the spin-pumping effects. The Cu capping layer significantly suppresses intermixing and possesses the lowest damping constant of 0.009. The micromagnetic simulations reveal that the low damping constant of CoFeB may result in the nucleation of domains at lower current density, and thus reduces J_C0. A reduction of 27% in J_C0 can be achieved by replacing the conventional Ta capping layer with a Cu layer.