產生和探測手徵性奈米磁性結構
Generation and detection of chiral magnetic nanostructures
Spintronic devices based on ferromagnetic materials, from high-density magnetic
recording to magnetic random access memories, have been the leading technologies for decades. Recently, spintronic phenomena and devices have evolved from exploiting spin-polarized current to pure spin current. However, the prospects of spin-orbit interaction for low-power spintronics, especially manipulation of pure spin current and electrical switching, remain perplexing and challenging.
In this joint program, we first demonstrate the manipulation of our spin current form ferromagnetic insulator, YIG, and report the effect of the demagnetizing field on the spin current transport. The demagnetizing factors play a vital role in the thickness and width dependence of transport behaviors, with an anomalous plateau associated with the spin current phenomenon, as seen from various independent measurements, including the spin Seebeck effect, spin Hall magnetoresistance, planar Hall effect, and magneto-optic Kerr effect. Therefore, the characteristics of spin current not only are sensitive to the surface magnetic property but also reflect the demagnetizing field of the specimen. This work is published in Physical Review B 102, 174426 (2020).
We also demonstrate 3d Cr with strong spin-orbit coupling can induce strong interfacial
perpendicular magnetic anisotropy (PMA), spin-orbit torque (SOT), and field-free SOT switching. This important result, which is recently published in Physical Review Applied 11, 061005 (2019) as a letter, will shed light on field-free SOT switching and uncover the significant role of 3d materials with a variety of functions for next generation spintronic devices.
從高密度磁記錄到磁隨機存取存儲器，基於鐵磁材料的自旋電子元件，一直以來是扮演應用於此類電子器件與相關領先技術的主要角色。而近年來，更新穎的自旋電子學現象和元件已經發展從利用自旋極化電流轉向到研究如何操控與激發純自旋電流，甚至不需要伴隨古典電荷電流的產生。然而，低功率自旋電子器件的開發和利用自旋軌道相互作用的相關機制，尤其是如何利用純自旋電流和電性而非磁場的操縱，仍然有許多困惑和挑戰。
在此聯合研究計畫中，我們首先成功的展示如何操縱鐵磁絕緣體YIG 的自旋電流，並首次發現退磁場對自旋電流傳輸的影響，退磁場在自旋電流傳輸行為不論是的樣品厚度和寬度都起著至關重要的作用，我們從各種獨立的測量觀測到相關的異常自旋電流現象，包括自旋塞貝克效應，自旋霍爾磁阻，平面霍爾效應和磁光克爾效應。因此，自旋電流的特性不僅對表面磁性敏感，而且反映了樣品的退磁場。這項重要工作已發表在Physical Review B 102，174426（2020）中。另外我們還證明了具有強自旋軌道耦合的3d Cr可以引起強界面垂直磁各向異性，實現了無須外加磁場的磁化翻轉轉換，這個重要的結果最近發表在Physical Review Applied 11，061005（2019），我們的研究結果將對發展下一代自旋電子器件扮演重要的作用。