2026 Liu SOT MRAM Magnetic Field Performance

Spin-orbit torque magnetic random-access memory (SOT-MRAM) possesses high speed, ultrahigh endurance, and excellent compatibility with advanced semiconductor manufacturing processes, making it a promising nonvolatile memory technology. This study addresses the intrinsic bias field (Hs) affecting the free layer in the magnetic tunnel junction (MTJ), which creates significant asymmetry in the critical current density for magnetization switching between two resistance states and subsequently increases energy consumption. Recent methods typically involve introducing additional magnetic layers to compensate for Hs, which raises manufacturing costs and limits practicality. Our proposed approach regulates the write current through local stray magnetic field engineering without altering the MTJ stack. Utilizing micromagnetic simulations for a SOT-MTJ with perpendicular magnetic anisotropy (PMA), we demonstrate that a ferromagnetic filling layer can significantly decrease write-current asymmetry and provide the necessary auxiliary field for deterministic switching. Furthermore, optimizing the bias-compensation effect decreases the write-current bias ratio from 21.6% to 1.3%. Importantly, this method enables field-free switching, essential for SOT-MTJ applications targeting high integration density, and shows exceptional scalability, maintaining a low write-current bias ratio even when sized down to approximately 10 nm.