Effect of Finite Tunneling Magnetoresistance for the Switching Dynamics in the Spin Transfer Torque Magnetic Tunneling Junctions

We investigate the effect of tunneling magnetoresistance (TMR) on the spin transfer-torque (STT) switching behaviors in magnetic tunneling junctions. In most of the micromagnetic simulations for STT switching, a uniform current density has been assumed, which is not realistic in the high TMR devices. The local STT is proportional to the local current density, and the local current density will be determined by the local resistivity. Since higher than 150% of TMR values is required in the real STT-magnetoresistive random access memory devices, the local resistance is dramatically changed as a function of the relative spin orientation between the fixed and free layers under the constant voltage operation mode. By employing non-uniform current density in STT switching simulations using the “embedded object-oriented micromagnetic framework” scheme, we found that the details of switching behaviors such as switching time and critical current density are significantly influenced by the TMR values.