R&D: Field-Free Spin–Orbit Torque Switching in Ferromagnetic Trilayers at Sub-ns Timescales

Nature Communications has published an article written by Qu Yang, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore, Donghyeon Han, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Korea, Shishun Zhao, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore, Jaimin Kang, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Korea, Fei Wang, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore, Sung-Chul Lee, Next Generation Process Development Team, Semiconductor R&D Center, Samsung Electronics Co. Ltd., Hwaseong, Gyeonggi, 18448, Korea, Jiayu Lei, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore, Kyung-Jin Lee, Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Korea, Byong-Guk Park, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Korea, and Hyunsoo Yang, Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.

Abstract: “Current-induced spin torques enable the electrical control of the magnetization with low energy consumption. Conventional magnetic random access memory (MRAM) devices rely on spin-transfer torque (STT), this however limits MRAM applications because of the nanoseconds incubation delay and associated endurance issues. A potential alternative to STT is spin-orbit torque (SOT). However, for practical, high-speed SOT devices, it must satisfy three conditions simultaneously, i.e., field-free switching at short current pulses, short incubation delay, and low switching current. Here, we demonstrate field-free SOT switching at sub-ns timescales in a CoFeB/Ti/CoFeB ferromagnetic trilayer, which satisfies all three conditions. In this trilayer, the bottom magnetic layer or its interface generates spin currents with polarizations in both in-plane and out-of-plane components. The in-plane component reduces the incubation time, while the out-of-plane component realizes field-free switching at a low current. Our results offer a field-free SOT solution for energy-efficient scalable MRAM applications.“