Effect of Shape Deformation by Edge Roughness in Spin-Orbit Torque Magnetoresistive Random-Access Memory

Abstract

We present a micromagnetic simulation study of shape deformation and edge roughness effect in the spin orbit torque-magnetic random access memory (SOT-MRAM). The two different write schemes, magnetic field induced SOT write scheme and SOT-spin transfer torque (STT) hybrid write scheme, were studied in the presence of the stray field from the reference layer. We found that for conventional magnetic field induced SOT, shape deformation can cause non-deterministic switching even at a relatively high gilbert damping constant of 0.08. Higher Gilbert damping constant (alpha) of 0.09 is needed to ensure deterministic switching under the shape deformation effect. The SOT-STT hybrid write scheme showed deterministic switching even at lower damping constant with relatively low device variations due to the constant -z directed torque of the STT. However, with higher damping constant of alpha = 0.1, device variation with the SOT-STT hybrid write scheme increases while the SOT-magnetic field write scheme successfully compensates the most of the variation caused by the edge deformation.