Controllable field-free switching of perpendicular magnetization through bulk spin-orbit torque in symmetry-broken ferromagnetic films

• Published in: Nature communications Vol. 12; no. 1; pp. 2473 - 10
• Main Authors: Xie, Xuejie, Zhao, Xiaonan, Dong, Yanan, Qu, Xianlin, Zheng, Kun, Han, Xiaodong, Han, Xiang, Fan, Yibo, Bai, Lihui, Chen, Yanxue, Dai, Youyong, Tian, Yufeng, Yan, Shishen
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.04.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 147/137; 639/301/119/1001; 639/766/1130/2798; 639/766/119/1001; Access control; Cobalt base alloys; Cobalt compounds; Composition; Domain walls; Energy efficiency; Ferromagnetic films; Ferromagnetic materials; Heterojunctions; Humanities and Social Sciences; Interlayers; Intermetallic compounds; Magnetic fields; Magnetism; Magnetization; Memory devices; multidisciplinary; Platinum compounds; Polarity; Science; Science (multidisciplinary); Spintronics; Stability; Switching (polarity); Symmetry; Torque
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-22819-4

Programmable magnetic field-free manipulation of perpendicular magnetization switching is essential for the development of ultralow-power spintronic devices. However, the magnetization in a centrosymmetric single-layer ferromagnetic film cannot be switched directly by passing an electrical current in itself. Here, we demonstrate a repeatable bulk spin-orbit torque (SOT) switching of the perpendicularly magnetized CoPt alloy single-layer films by introducing a composition gradient in the thickness direction to break the inversion symmetry. Experimental results reveal that the bulk SOT-induced effective field on the domain walls leads to the domain walls motion and magnetization switching. Moreover, magnetic field-free perpendicular magnetization switching caused by SOT and its switching polarity (clockwise or counterclockwise) can be reversibly controlled in the IrMn/Co/Ru/CoPt heterojunctions based on the exchange bias and interlayer exchange coupling. This unique composition gradient approach accompanied with electrically controllable SOT magnetization switching provides a promising strategy to access energy-efficient control of memory and logic devices. A major challenge of spintronics is achieving magnetic field free electrical control of magnetisation. Here, Xie et al. achieve perpendicular magnetisation switching in a CoPt alloy, breaking inversion symmetry by varying the composition of the alloy in the growth direction.