Field-free picosecond spin–orbit torque switching of a novel cylindrical magnetic tunnel junction

Abstract

The development of high-density, field-free spin–orbit torque (SOT) magnetic random access memory (MRAM) at sub-5 nm technology nodes is crucial for next-generation memory technologies. Here, we propose a novel cylindrical magnetic tunnel junction (C-MTJ) architecture, where a nano-shell free layer coaxially surrounds a central heavy-metal nanorod. Through a synergistic approach combining atomistic spin dynamics, micromagnetic simulations, and analytical modeling, we establish the magnetic ground state phase diagram for this geometry down to a 3 nm radial dimension, identifying the out-of-plane Z-state as a stable and scalable configuration. We demonstrate that a single 50 ps current pulse can trigger deterministic, field-free magnetization reversal in under 500 ps, showcasing the C-MTJ’s potential for ultrafast operation. Furthermore, we employ a deep neural network as a surrogate model to rapidly optimize device performance, revealing a design pathway to reduce the critical switching current by an order of magnitude. This C-MTJ design, with its unique 3D geometry and efficient SOT switching, offers a promising pathway toward ultrafast, high-density MRAM and neuromorphic devices.