Generation of high and bidirectional out-of-plane spin–orbit torque through vertical magnetization gradient

IF 3.5 2区物理与天体物理 Q2 PHYSICS, APPLIED

Applied Physics Letters Pub Date : 2025-03-31 DOI:10.1063/5.0251658

Tianli Jin, Yuliang Zhu, Shaomin Li, Bo Zhang, Funan Tan, Gerard Joseph Lim, Jiangwei Cao, Kaiming Cai, Wen Siang Lew

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引用次数: 0

Abstract

High efficiency and out-of-plane spin–orbit torque (OOP-SOT) driven magnetization switching is essential for developing spin-based memory and logic devices. In this study, we report the generation of a large charge-to-spin conversion and bidirectional OOP-SOT by engineering a vertical magnetization gradient within a Co/Ho multilayer system. Exploiting the antiferromagnetic coupling between Co and Ho, the magnetization gradient up to 16.8 (emu/cm−3)/nm was achieved by gradually varying the Ho layer thickness from 0.4 to 0.9 nm. The presence of the OOP-SOT was confirmed through Hall resistance-field loop shift measurements, which has been attributed to the broken symmetry in spin current reflection and transmission in the Co/Ho multilayer with vertical magnetic property gradients. Additionally, the effective field of the OOP-SOT is strongly correlated with the direction of the magnetization gradient, measured to be around +0.7 and –2.5 Oe/mA for the positive and negative magnetization gradients, respectively. Furthermore, the largest SOT in the Co/Ho multilayer with a negative gradient was observed compared to the positive gradient and uniform Co/Ho multilayer structures. The enhanced SOT is attributed to the bulk Rashba field generated by the gradient structure, along with increased spin polarization. The results demonstrated here provide a promising approach for utilizing magnetization gradients for the development of efficient, current-driven spin-based storage and logic devices.

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来源期刊

Applied Physics Letters 物理-物理：应用

CiteScore

6.40

自引率

10.00%

发文量

1821

审稿时长

1.6 months

期刊介绍： Applied Physics Letters (APL) features concise, up-to-date reports on significant new findings in applied physics. Emphasizing rapid dissemination of key data and new physical insights, APL offers prompt publication of new experimental and theoretical papers reporting applications of physics phenomena to all branches of science, engineering, and modern technology. In addition to regular articles, the journal also publishes invited Fast Track, Perspectives, and in-depth Editorials which report on cutting-edge areas in applied physics. APL Perspectives are forward-looking invited letters which highlight recent developments or discoveries. Emphasis is placed on very recent developments, potentially disruptive technologies, open questions and possible solutions. They also include a mini-roadmap detailing where the community should direct efforts in order for the phenomena to be viable for application and the challenges associated with meeting that performance threshold. Perspectives are characterized by personal viewpoints and opinions of recognized experts in the field. Fast Track articles are invited original research articles that report results that are particularly novel and important or provide a significant advancement in an emerging field. Because of the urgency and scientific importance of the work, the peer review process is accelerated. If, during the review process, it becomes apparent that the paper does not meet the Fast Track criterion, it is returned to a normal track.