Comprehensive Comparison of Switching Models for Perpendicular Spin-Transfer Torque MRAM Cells

Abstract

Simulations of free-layer switching in spin - transfer torque MRAM are usually performed with the torque computed approximately by assuming a position-independent electric current density through the structure. For high values of the tunneling magnetoresistance, this description is not accurate anymore, and one needs to solve the spin and charge drift-diffusion equations in the whole structure self-consistently. We compute the switching time distribution obtained by the self-consistent model and compare it to the switching times from the fixed current density approach. We show that, provided the current is appropriately adjusted, the simplified model can mimic the correct switching time distribution even in the case of high TMR.