Accurate Torque Evaluation in Elongated Ultra-Scaled STT-MRAM Devices

Abstract

We compute the spin torque acting on elongated magnetic layers inrecently proposed ultra-scaled STT-MRAM devices. For thispurpose we evaluate the non-equilibrium spin accumulation bysolving the coupled spin and charge transport equations. This goesbeyond the Slonczewski torque approximation which describestorques localized at the interface of the tunnel barrier and themagnetic free layer as well as the Zhang-Li torque approximationmodeling the torque acting on a magnetic texture (a domain wall)in the layer's bulk. We show that the torque contributions frominterface and bulk are not independent from each other and ourgeneralized approach is necessary to accurately model the torquein the presence of a magnetic domain wall inside the magnetic freelayer. We implemented a numerical solution of the spin and chargetransport equations in a finite element-based framework.