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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/9412

Title: 合成自由層於軸向自旋極化電流下之磁動力學
Magnetodynamics of Composite Free Layers under Axial Spin-Polarized Currents
Authors: 楊志信
Contributors: NTOU:Institute of Optoelectronic Sciences
Keywords: 自旋移轉力矩;電流誘發磁化翻轉;微磁學模擬;合成自由層;雙重自旋濾波器
Spin transfer torque;current-induced magnetization switching;micromagnetic simulation;composite free layer;dual spin-filter
Date: 2009-08
Issue Date: 2011-06-28T07:06:42Z
Publisher: 行政院國家科學委員會
Abstract: 摘要:當自旋極化電流垂直通過鐵磁層時,傳導電子的自旋將再極化因而產生一力矩作用於當地磁 矩。這自旋移轉力矩提供只需用電流但不需外施磁場就能有效地操控磁化之新穎方法,並由於其豐 富的基礎物理及技術應用的潛能,已激起人們相當的興趣。理論預測顯示自旋力矩驅動磁化翻轉之 臨界電流將隨鐵磁體的體積減少而降低,因此此一嶄新的磁化翻轉對高密度磁性隨機存取記憶體提 供一可調尺度化之寫入方案。然而已實現的臨界電流密度仍然不吸引人地偏高,而無法與現今的半 導體技術匹配;因此欲實用化此一應用必須作多方面的研究努力,緣此全盤瞭解自由層於自旋移轉 力矩作用下之磁動力學翻轉行為是值得的。在此計畫中我們提出一新潁的結構,即兩固定極化層位 於合成自由雙層之兩側,可望降低翻轉電流。我們額外考慮厄斯特場及熱散亂場,運用微磁學理論 以研究臨界翻轉電流及翻轉時間與自由層之磁性參數及相對厚度、自由層之層間偶合、兩固定層磁 化之平行或反平行排列、電流頻率以及脈衝時間等之相依性,這目的就是要找出降低自由層藉電流 誘發磁化翻轉所需寫入電流之最佳策略。
Abstract:When a spin polarized current flows perpendicularly through a magnetic multilayer, the spin of conduction electrons will be repolarized and then a torque is exerted to the local moment. The spintransfer torque offers a novel method to effectively manipulate the state of magnetization using only the charge current without any external magnetic field, which has stimulated considerable interest due to its rich basic physics and potentials for technologic applications. Theoretical prediction suggests that the critical current for spin-torque driven magnetization switching decreases with decreasing ferromagnet volume, and then this new magnetization switching provides a scalable write scheme in high-density magnetic random access memory. However the achieved critical current density is still unattractively high to match the existing semiconductor technology, extensive research effects should be done to realize this application. Therefore, it is deserved to fully understand the magneto- dynamic switching behavior of free layers under the action of the spin transfer torque. In this project, we propose a novel architecture, i.e., the two fixed polarizing layers lying on the both side of the composite free layer, seeking to lower the switching current. The micromagnetic theory is employed to study the dependence of the critical switching current and switching time on the magnetic parameters and the relative thickness of free layers, the interlayer coupling between the free layers, the parallel or antiparallel alignment of two fixed-layer magnetizations, current frequency, and pulse duration, in addition taken into account of the Oersted fields and thermal random field. The aim is to find an optimal strategy to minimize the write current for the current-induced magnetization switching of free layers.
Relation: NSC98-2112-M019-005
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/9412
Appears in Collections:[光電科學研究所] 研究計畫

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