Cooperative STT and SOT switching in perpendicular magnetic tunnel junctions: Role of the pulse-end magnetization state
Abstract
Spin--orbit torque MRAM (SOT-MRAM) is a leading candidate for next-generation nonvolatile memory, offering high speed, endurance, and architectural compatibility. However, in conventional SOT switching, the magnetization remains near the in-plane region at pulse termination, making the final state highly sensitive to post-pulse relaxation dynamics and prone to back-switching. To overcome this, we propose a field-free scheme in which the transverse SOT drives large-angle precessional excitation while the perpendicular spin-transfer torque (STT) biases the trajectory toward the reversed −z state. Micromagnetic simulations reveal a nonlinear switching boundary in the JSTT--JSOT parameter space, originating from the distinct dynamical roles of the two torques: SOT primarily governs the excitation and crossing of the dynamical separatrix, whereas STT controls the terminal trajectory and final-state selection. An analytical macrospin model, based on the stability analysis of the current-induced equilibrium, reproduces the critical-boundary trends as functions of current density, Gilbert damping α, and uniaxial anisotropy Ku, and distinguishes dynamic anti-damping and static instability branches. Systematic analyses of pulse duration, damping, anisotropy, and the STT--SOT balance further demonstrate that reliable ultrafast switching requires not only sufficient excitation to cross the separatrix before pulse termination, but also precise control of the pulse-end magnetization state to minimize post-pulse relaxation. These results establish that the pulse-end state, rather than the instantaneous torque amplitude, is the decisive factor governing switching speed and reliability in coupled STT--SOT systems.
Related
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- Effects of Longitudinal Spin Current Density Gradient on Spin-Orbit Torque Switching of Perpendicular Magnetization
- Orbital and Spin–Orbit Torque Interplay in Ta/W-Based Magnetic Tunnel Junctions with Vertical Nonlocal Switching
- Giant orbital torque-driven picosecond switching in magnetic tunnel junctions
- Perpendicular Magnetization from Crystallite Boundaries in Polycrystalline Antiferromagnetic γ-FeMn
BibTeX
@misc{zhu2026cooperative,
title = {{Cooperative STT and SOT switching in perpendicular magnetic tunnel junctions: Role of the pulse-end magnetization state}},
author = {Zeyi Zhu and Ding Ma and Kai Zhang and Mingwei Wu and Yi Huang and Jiarui Niu and Shuai Zhang and Mengdi Yin and Ka-San Mak and Lina Chen and Bo Liu and Tiejun Zhou and Yongbing Xu and Ronghua Liu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11191},
eprint = {2610.11191},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11191},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Cooperative STT and SOT switching in perpendicular magnetic tunnel junctions: Role of the pulse-end magnetization state
AU - Zeyi Zhu
AU - Ding Ma
AU - Kai Zhang
AU - Mingwei Wu
AU - Yi Huang
AU - Jiarui Niu
AU - Shuai Zhang
AU - Mengdi Yin
AU - Ka-San Mak
AU - Lina Chen
AU - Bo Liu
AU - Tiejun Zhou
AU - Yongbing Xu
AU - Ronghua Liu
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11191
UR - https://arxiv.org/abs/2610.11191
AB - Spin--orbit torque MRAM (SOT-MRAM) is a leading candidate for next-generation nonvolatile memory, offering high speed, endurance, and architectural compatibility. However, in conventional SOT switching, the magnetization remains near the in-plane region at pulse termination, making the final state highly sensitive to post-pulse relaxation dynamics and prone to back-switching. To overcome this, we propose a field-free scheme in which the transverse SOT drives large-angle precessional excitation while the perpendicular spin-transfer torque (STT) biases the trajectory toward the reversed −z state. Micromagnetic simulations reveal a nonlinear switching boundary in the J_STT--J_SOT parameter space, originating from the distinct dynamical roles of the two torques: SOT primarily governs the excitation and crossing of the dynamical separatrix, whereas STT controls the terminal trajectory and final-state selection. An analytical macrospin model, based on the stability analysis of the current-induced equilibrium, reproduces the critical-boundary trends as functions of current density, Gilbert damping α, and uniaxial anisotropy K_u, and distinguishes dynamic anti-damping and static instability branches. Systematic analyses of pulse duration, damping, anisotropy, and the STT--SOT balance further demonstrate that reliable ultrafast switching requires not only sufficient excitation to cross the separatrix before pulse termination, but also precise control of the pulse-end magnetization state to minimize post-pulse relaxation. These results establish that the pulse-end state, rather than the instantaneous torque amplitude, is the decisive factor governing switching speed and reliability in coupled STT--SOT systems.
ER -