Multi-scale modelling of current-induced switching in magnetic tunnel junctions using ab initio spin transfer torques

摘要

There exists a significant challenge in developing efficient magnetic tunneljunctions with low write currents for non-volatile memory devices. With the aimof analysing potential materials for efficient current-operated magneticjunctions we have developed a multi-scale methodology combining the ab initiocalculations of spin-transfer torque with large-scale time-dependentsimulations using atomistic spin dynamics. In this work we introduce ourmulti-scale approach including a discussion on a number of possible mappingschemes the ab initio spin torques into the spin dynamics. We demonstrate thismethodology on a prototype Co/MgO/Co/Cu tunnel junction showing that the spintorques are primarily acting at the interface between the Co free layer andMgO. Using spin dynamics we then calculate the reversal switching times for thefree layer and the critical voltages and currents required for such switching.Our work provides an efficient, accurate and versatile framework for designingnovel current-operated magnetic devices, where all the materials details aretake into account.