Geometric variance studies of spin-orbit torque magnetic random access memory

Abstract

We demonstrate the effect of shape deformation in spin-orbit torque magnetic random access memory (SOT-MRAM) based on micromagnetic simulation by generating 1000 randomly deformed samples using the exponentially decaying autocorrelation function. The conventional in-plane magnetic field-assisted SOT write scheme and the recently proposed spin-transfer torque-spin-orbit torque (STT-SOT) write scheme were simulated and compared with the effect of the Gilbert damping constant ($\alpha$) considered in the presence and the absence of the Dzyaloshinskii-Moriya interaction (DMI) and stray field. We found that shape deformation of the MTJ can result in write failure or degradation of the switching time. To compensate the device-to-device performance variation induced by the shape deformation, the condition of high alpha and the presence of the DMI is desired for the magnetic field-assisted write scheme. The STT-SOT write scheme shows slight improvement in the switching performance for the larger alpha and shows write failure when the stray field is present while it retains 100% switching probability even with small alpha regardless of the DMI.