Spin-flip scattering in magnetic tunnel junctions: From current-voltage characteristics to spin-transfer torque

We examine room temperature current-voltage (IV) characteristics of CoFeB|MgO|CoFeB type of perpendicularly magnetized tunnel junctions developed for memory applications. From their nonlinear bias voltage dependence, a conductance "cross-scaling"is seen that is consistent with the involvement of inelastic spin-flip scattering in electrodes. A phenomenological model is constructed that connects the parameters of spin-flip scatter-related inelastic events with both magnetoresistance and spin-transfer torque. The model provides measurable, electrode-specific properties such as interface exchange stiffness as it affects spin-torque performance.