Current-Induced Magnetization Switching in MgO Barrier Based Magnetic Tunnel Junctions with CoFeB/Ru/CoFeB Synthetic Ferrimagnetic Free Layer

Abstract

We report the intrinsic critical current density (Jc0) in current-induced\nmagnetization switching and the thermal stability factor (E/kBT, where E, kB,\nand T are the energy potential, the Boltzmann constant, and temperature,\nrespectively) in MgO based magnetic tunnel junctions with a\nCo40Fe40B20(2nm)/Ru(0.7-2.4nm)/Co40Fe40B20(2nm) synthetic ferrimagnetic (SyF)\nfree layer. We show that Jc0 and E/kBT can be determined by analyzing the\naverage critical current density as a function of coercivity using the\nSlonczewski's model taking into account thermal fluctuation. We find that high\nantiferromagnetic coupling between the two CoFeB layers in a SyF free layer\nresults in reduced Jc0 without reducing high E/kBT.\n