Field‐Free Spin‐Orbit Torque Switching in Synthetic Ferro and Antiferromagents with Exchange Field Gradient. (5th February 2023)

• Record Type: Journal Article
• Authors: Fan, Haodong; Jin, Menghao; Luo, Yongming; Yang, Hongxin; Wu, Birui; Feng, Zhongshu; Zhuang, Yanshan; Shao, Ziji; Yu, Changqiu; Li, Hai; Wen, Jiahong; Wang, Ningning; Liu, Bo; Li, Wenjun; Zhou, Tiejun
• Is Part Of: Advanced functional materials. Volume 33:Number 16(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-05
• Subjects: exchange field gradients -- field‐free switching -- spin‐orbit torque -- synthetic antiferromagnets; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202211953
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Deterministic switching of perpendicularly magnetized synthetic antiferromagnets using spin‐orbit torque (SOT) usually requires an in‐plane auxiliary magnetic field, which limits its practical applications. Here, an exchange field gradient is introduced into perpendicularly magnetized synthetic ferro‐ and antiferromagnets (SFs and SAFs) through the insertion of a slightly wedged Ru between two thin ferromagnetic layers, which induces field‐free switching of perpendicular SFs and SAFs with a switching ratio up to 81% regardless of the nature of the coupling. Temperature‐dependent measurement shows a robust field‐free switching even at low temperature. The experimental results show that the field‐free switching ratio and the effective SOT field are directly related to the exchange field gradient. The theoretical model and numerical simulation indicate that the dynamic noncollinear spin textures induced by the exchange field gradient lead to the field‐free switching, while the sign of the exchange field gradient determines the field‐free switching polarity. It is further revealed that the SOT efficiency is positively correlated with the antiferromagnetic exchange field for both Ru wedged and non‐wedged samples. These results provide a new avenue for simultaneously achieving field‐free switching and high SOT efficiency of perpendicularly magnetized SAFs for highly stable, high‐density, low‐stray‐field, and low‐power magnetic memory devices. Abstract : An exchange field gradient caused by the slightly wedged Ru is introduced into perpendicularly magnetized synthetic ferro‐ and antiferromagnets, resulting in large field‐free switching ratio and high spin‐orbit torque (SOT) efficiency. The dynamic noncollinear spin textures induced by the exchange field gradient lead to the field‐free switching. A new avenue is provided for simultaneously achieving field‐free switching and high SOT efficiency for low‐power magnetic memory devices.