Current-Driven Magnetization Switching in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

Abstract

Current-driven magnetization switching in low-resistance Co 40 Fe 40 B 20 /MgO/Co 40 Fe 40 B 20 magnetic tunnel junctions (MTJs) is reported. The critical-current densities J c required for current-driven switching in samples annealed at 270 and 300°C are found to be as low as 7.8×10 5 and 8.8×10 5 A/cm 2 with accompanying tunnel magnetoresistance (TMR) ratios of 49 and 73%, respectively. Further annealing of the samples at 350°C increases TMR ratio to 160%, while accompanying J c increases to 2.5×10 6 A/cm 2 . We attribute the low J c to the high spin-polarization of tunnel current and small M s V product of the CoFeB single free layer, where M s is the saturation magnetization and V the volume of the free layer.