Reduction of switching current by spin transfer torque effect in perpendicular anisotropy magnetoresistive devices (invited)

Spin transfer torque-based magnetic random access memory with perpendicular magnetic anisotropy (PMA) provides better scalability and lower power consumption compared to those with in-plane anisotropy. Spin transfer torque switching in magnetoresistive spin valves with PMA is investigated. The hard layer is made of (Co/Pd) multilayer, whereas the soft layer is a lamination of (CoFe/Pd) and (Co/Pd). By the insertion of an in-plane spin polarizer adjacent to the perpendicular anisotropy free layer, thus creating a modified-dual spin valve, a significant reduction of about 40 in the current density required for spin torque transfer switching was observed. By using a spin polarized current with different pulse widths down to 10 ns, the barrier energy E_B in 100-nm-diameter devices was found to be reduced from 1.1 to 0.43 eV. Besides the reduction of switching current density in a device with PMA, the new structure shows a clear increase in magnetization switching speed as revealed by micromagnetic simulation.