Thermal Stability and Depinning Currents of Domain Wall-Based Artificial Synapses

Abstract: Micromagnetic modeling is employed to optimize the design of artificial synapse devices based on the spin-orbit-torque (SOT) driven domain wall (DW) motion along a nanotrack with triangular notches. Key attributes, such as the thermal stability of the pinned DW and depinning currents, are obtained for varied nanotrack geometry and pinning strength. Depinning probability as a function of SOT current density and pulse width is studied using finite temperature micromagnetic simulations for varying pinning potential. Results show that wider notches provide better thermal stability - depinning current trade-off. On the other hand, narrow notches exhibit less variation in the depinning times at finite temperatures. It is observed that the DW position can be set precisely to any desired location by the SOT current pulse if the thermal stability is sufficiently high. It is also observed that the meta-plastic functionality can be obtained by adding notches of progressively higher depinning currents along the rectangular nanotrack.