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

Abstract

Current-driven magnetization switching in low-resistance Co₄₀Fe₄₀B₂₀/MgO/Co₄₀Fe₄₀B₂₀ 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 7.8×10⁵ and 8.8×10⁵ A/cm² 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 2.5×10⁶ A/cm². 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.