Simulation of multilevel magnetic data storage via domain wall nucleation

We present micromagnetic simulations of spin–orbit torque (SOT)-induced multistate magnetization switching in a ferromagnetic layer with perpendicular anisotropy, conducted without an external magnetic field. Four volatile states are excited by a constant current. Each volatile state, after the removal of the current and undergoing relaxation and stabilization, can transition into one of four stable nonvolatile states. Further analysis revealed that, by specifically controlling the amplitude and active/inactive intervals of a rectangular pulse, a volatile state can transition to a robust nonvolatile state, providing a viable approach for multilevel magnetic data storage. The resistance of each magnetic domain state is qualitatively calculated, and their differences make these multilevel states detectable for information reading.