Reduction in critical current density of current-induced magnetization switching

We have investigated the current-induced magnetization switching in an exchange-biased spin valve structure. By using an unpatterned antiferromagnetic layer to pin the fixed Co layer, we obtained a lower switching current density by a factor of 5 than a simple spin valve structure. For the application, it is important to know how to keep the spin polarization when the thicker layer is pinned by an antiferromagnet. The unpatterned pinned ferromagnetic lead can be a good solution for spin-transfer-torque-activated device. The effect of Cu buffer layer on the top of the thin Co and Ru buffer layer under the thick Co layer on the current-induced magnetization switching in cobalt-based trilayer spin valves was also investigated. The experimental results showed that the Ru buffer layer in combination with Cu buffer layer could induce a decrease in the critical switching current by 30%, and an increase in the absolute resistance change by 35%, which is caused by an improvement of a microstructure of a thicker Co polarizer.