本文關鍵詞：磁疇壁結構動力學及其應用研究　出處：《蘭州大學》2016年博士論文　論文類型：學位論文

  更多相關文章： 磁疇壁 斯格明子 自旋轉移矩效應 自旋納米振蕩器 賽道存儲器 自旋波

【摘要】：自旋電子學將電子的自旋屬性和電荷屬性緊密地聯(lián)系了起來,這兩個自由度的結合為開發(fā)性能優(yōu)異的電子器件提供了更廣闊的空間。賽道存儲器,自旋納米振蕩器,STT-MRAM就是其中三種典型的自旋電子學器件,有著巨大的應用前景,然而在實現(xiàn)應用之前仍有一些問題需要解決。本論文主要通過微磁學模擬和實驗的手段,針對賽道存儲器和自旋納米振蕩器等自旋電子學器件遇到的一些問題進行研究。(一)賽道存儲器問題研究Parkin起初設計的賽道存儲器是基于面內(nèi)磁化納米帶中的180度疇壁。相比之下,基于360度疇壁的賽道存儲器具有更高的存儲密度和較強的抗磁場干擾能力。在第三章中,我們首先設計了簡單的產(chǎn)生360度疇壁的電極結構并通過微磁學模擬發(fā)現(xiàn),要成功產(chǎn)生360度疇壁,電流脈沖的下降過程需要緩慢降低以防止疇壁湮滅。然后利用平行納米帶中360度疇壁和180度疇壁的耦合,或者兩個360度疇壁的耦合提高了360度疇壁的穩(wěn)定性,從而使360度疇壁的極限速度提高了81.1%。第四章中,我們研究了磁振子(自旋波)與360度疇壁的相互作用,自旋波的傳播過程沒有電荷輸運,所以為解決焦耳熱的問題提供了一種新的思路。微磁學模擬研究發(fā)現(xiàn),自旋波也可以驅動360度疇壁運動,而且根據(jù)材料參數(shù)和自旋波頻率的不同,疇壁可以沿著自旋波方向或者反方向運動。此外,通過被360度疇壁反射的自旋波研究了自旋波的多普勒效應。通過透射自旋波研究了自旋波的相位移動效應。垂直各向異性材料納米帶中的疇壁寬度非常窄,而且臨界電流密度也比面內(nèi)磁化樣品中要低,所以非常有利于提高賽道存儲器的存儲密度并降低功耗。產(chǎn)生磁疇壁是研究其應用的一個非常關鍵的步驟,傳統(tǒng)上是利用一個與納米帶垂直的直線電極來產(chǎn)生疇壁。第五章中,我們提出了一個非常高效的在垂直各向異性納米帶中注入磁疇的Π型的電極結構。這種方法可以用5.35×1011 A/m2的電流脈沖在15 ns的脈沖時間內(nèi)在Co/Ni多層膜中成功產(chǎn)生一個磁疇。實驗和計算結果都證明這種方法的能耗只有傳統(tǒng)方法的30%左右。最后,我們通過反常霍爾效應測量了磁疇壁在十字叉結構處的釘扎和脫釘扎現(xiàn)象,并通過電流對脫釘扎場進行了調(diào)控。(二)自旋納米振蕩器問題研究自旋納米振蕩器有很多非常優(yōu)異的性能,然而其輸出功率是一個瓶頸問題,現(xiàn)在有一種非常好的解決思路就是制作振蕩器陣列,然后通過多個振蕩器信號的疊加來提高輸出功率。第六章中,我們研究了點電流驅動隧道結結構中磁Skyrmion的振蕩,并依此原理設計了一種新型的基于磁Skyrmion的自旋納米振蕩器。該振蕩器可以在一個器件中同時輸出多路信號,故而有望提高振蕩器的輸出功率。信號的線寬可以小于1 MHz。此外,該電極可以在108 A/m2的電流密度下工作且工作頻率最小可以接近0 MHz,最大可以到GHz量級。
[Abstract]:Spin electronics closely links the spin and charge properties of electrons. The combination of these two degrees of freedom provides a wider space for the development of excellent electronic devices. Spin nanometer oscillator (STT-MRAM) is one of the three typical spin electronics devices, which has a great application prospect. However, there are still some problems to be solved before the application. Some problems encountered by spin electronics devices such as racetrack memory and spin nanometer oscillator are studied. (1). Research on racetrack memory problem Parkin originally designed the racetrack memory based on the 180-degree domain walls in the in-plane magnetized nanobelts. Track memory based on 360-degree domain walls has higher storage density and stronger resistance to magnetic field interference. In Chapter 3. We first designed a simple electrode structure to generate 360-degree domain walls and found that it was necessary to successfully generate 360-degree domain walls by micromagnetic simulation. In order to prevent domain wall annihilation, the current pulse drop process needs to be slowly reduced, and then the coupling of 360 degree domain wall and 180 degree domain wall in parallel nanoribbons is used. Or the coupling of two 360-degree domain walls improves the stability of the 360-degree domain walls, thus increasing the limit speed of the 360-degree domain walls by 81.1. 4th. We study the interaction between magnetic oscillator (spin wave) and 360-degree domain wall. There is no charge transport in the propagating process of spin wave. It provides a new way to solve the problem of Joule fever. The micromagnetic simulation results show that the spin wave can also drive 360 degree domain wall motion, and according to the material parameters and the frequency of spin wave. The domain walls can move either in the spin direction or in the opposite direction. The Doppler effect of spin wave is studied by the reflection of 360 degree domain wall and the phase shift effect of spin wave is studied by transmission spin wave. The width of domain wall in vertical anisotropic nanobelts is very narrow. And the critical current density is lower than that in the in-plane magnetized sample, so it is very helpful to improve the storage density and reduce the power consumption of the racetrack memory. The generation of magnetic domain wall is a very important step to study its application. Traditionally, a linear electrode perpendicular to the nanobelts is used to generate domain walls. Chapter 5th. In this paper, we propose a highly efficient electrode structure for injecting magnetic domains into vertically anisotropic nanoribbons with a current pulse of 5.35 脳 1011 A / m ~ 2 and a current pulse of 15 脳 10 ~ (11) A / m ~ (2). A magnetic domain was successfully generated in the Co/Ni multilayer in the pulse time of ns. The experimental and computational results show that the energy consumption of this method is only about 30% of that of the traditional method. The phenomenon of pinning and de-pinning of magnetic domain wall at cross cross structure is measured by anomalous Hall effect. The spin nanometer oscillator has a lot of excellent performance, but its output power is a bottleneck problem. Now there is a very good solution to the idea is to make an oscillator array, and then through the superposition of multiple oscillator signals to improve the output power. Chapter 6th. We study the oscillations of magnetic Skyrmion in a point-current-driven tunnel junction. Based on this principle, a novel spin nanoscilloscope oscillator based on magnetic Skyrmion is designed, which can output multiple signals simultaneously in a single device. Therefore, it is expected to increase the output power of the oscillator. The line width of the signal can be less than 1 MHz. The electrode can work at a current density of 108A / m ~ 2 and the minimum operating frequency can be close to 0 MHz, and the maximum working frequency can be up to the order of GHz.
【學位授予單位】：蘭州大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O342

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1 趙曉雨;雷曉蔚;;二維伊辛模型的疇壁動力學[J];原子與分子物理學報;2011年02期

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