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

摘要

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℃ are found to be as low as 7.8 x 10~5 and 8.8 x 10~5 A/cm~2 with accompanying tunnel magnetoresistance (TMR) ratios of 49 and 73%, respectively. Further annealing of the samples at 350℃ increases TMR ratio to 160%, while accompanying J_c increases to 2.5 x 10~6 A/cm~2. We attribute the low J_c to the high spin-polarization of tunnel current and small MSV product of the CoFeB single free layer, where M_s is the saturation magnetization and V the volume of the free layer.