Researchers from Huazhong University of Science and Technology, in collaboration with Hubei University and Shandong University, have developed an innovative programmable spin-logic gate that operates without initialization. This groundbreaking device leverages spin-orbit torque (SOT) to achieve magnetization switching, assisted by an in-plane Oersted field generated by an integrated bias-field Au line. The findings, published in Engineering, offer a new approach for spin-logic operations in in-memory computing (IMC) architectures.

Traditional computing architectures, based on the Von Neumann model, present limitations in processing speed and power consumption due to the separation of storage and computing functions. In recent years, various non-volatile memory technologies, including magnetic random-access memory (MRAM), have been explored to address these challenges. Among them, spin-orbit torque (SOT) MRAM has garnered significant attention for its potential to construct IMC devices with near-infinite endurance and reduced power consumption.

However, performing complete Boolean logic operations with spintronic devices typically requires an initialization process, which can significantly slow down processing speed and increase power consumption. To overcome this limitation, the research team conceptualized and experimentally demonstrated a programmable and initialization-free spin-logic gate. This gate, fabricated as a Hall bar, allows complete Boolean logic operations without the need for initialization.

The core of the spin-logic gate consists of an SOT device and an Au line, which is electrically isolated from the SOT device by a dielectric layer. When currents are applied to the Au line, an in-plane Oersted field is generated within the SOT device region. This field assists the current flowing through the heavy metal (HM) layer of the SOT device to induce deterministic switching of the ferromagnet (FM) layer’s magnetization via the SOT effect. The switching polarity of the heterostructure is controlled by the orientation of the in-plane bias field produced by the currents flowing through the Au line.

In their experiments, the researchers used a W/CoFeB/MgO heterostructure with perpendicular magnetic anisotropy (PMA). By programming the current directions along the Au line and the HM layer, they demonstrated the execution of all 16 complete Boolean logic types. This allows logic operations to be performed in one step by simultaneously applying inputs without initialization. The device exhibited excellent reliability, repeatability, and reproducibility during logic operations.

The research also evaluated the potential for scaling down the device dimensions to reduce power consumption. By miniaturizing the logic device to the size of a magnetic tunnel junction (MTJ) and utilizing FinFET technology, the driving current can be significantly lowered, making it suitable for practical control transistors. This approach not only enhances the energy efficiency of the device but also maintains its high-speed operation capabilities.

The successful demonstration of an initialization-free programmable spin-logic gate represents a significant step forward in the practical application of spin-logic devices. This work provides a promising outlook for the integration of non-volatile spin-logic into IMC architectures, potentially overcoming the limitations of traditional computing models.

The paper “Initialization-Free Programmable Spin-Logic Gate in a Single Spin-Orbit Torque Device,” is authored by Jie Lin, Shuai Zhang, Shihao Li, Yan Xu, Xin Li, Wei Duan, Jincheng Hou, Chenxi Zhou, Wei Zhan, Zhe Guo, Min Song, Xiaofei Yang, Yufeng Tian, Xuecheng Zou, Dan Feng, Long You. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.022. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.