Influence of Current Redistribution in Switching Models for Perpendicular STT-MRAM

Abstract

Simulation of switching in spin-transfer torque magnetoresistive random access memory is usually performed by assuming that the torque is created by a position- and time-independent current density. However, in real circuits the voltage is fixed, not the current density. The assumption of a fixed current density, especially in modern devices with a tunneling magnetoresistance up to 200%, becomes thus questionable. In this work we compare the switching time distribution obtained under the assumptions of fixed voltage and fixed current density for a wide range of tunneling magnetoresistance and surface area values. We demonstrate that the approximate fixed current density approach can reproduce the correct switching times, provided that the current value is appropriately adjusted. We show that the correction on the current depends on the switching speed, dictated by different system parameters.