本文選題：自旋動(dòng)力學(xué)方法 + 鐵磁納米條　； 參考：《揚(yáng)州大學(xué)》2014年碩士論文

【摘要】：使用極化電流操控磁性材料中的疇壁運(yùn)動(dòng)在開發(fā)新一代固態(tài)數(shù)據(jù)存儲(chǔ)器、邏輯器件和微波器件方面有著很重要的潛在應(yīng)用。由自由電子引起的自旋轉(zhuǎn)移力矩效應(yīng)導(dǎo)致的疇壁運(yùn)動(dòng)在理論和實(shí)驗(yàn)上都獲得了充分的研究。目前面臨一個(gè)主要的問題是對(duì)于實(shí)際應(yīng)用驅(qū)動(dòng)疇壁持續(xù)運(yùn)動(dòng)所需的電流太大。最近,有研究者發(fā)現(xiàn)增加磁性系統(tǒng)中的垂直各向異性可以增強(qiáng)橫向疇壁的運(yùn)動(dòng)。然而相應(yīng)的物理機(jī)制并沒有獲得清楚的解釋。在磁性納米帶系統(tǒng)中,渦旋疇壁是一種基本的疇壁類型。電流驅(qū)動(dòng)渦旋疇壁除了會(huì)發(fā)生沿納米帶長(zhǎng)度方向的運(yùn)動(dòng)還伴隨著渦旋中心垂直于納米帶方向的運(yùn)動(dòng),因而渦旋疇壁的運(yùn)動(dòng)比橫向疇壁更加復(fù)雜。從理論講,相比于橫向疇壁研究渦旋疇壁的運(yùn)動(dòng)可以獲得更加豐富的物理機(jī)制。此外,在高密度的數(shù)據(jù)存儲(chǔ)器設(shè)計(jì)中,納米線與納米線之間的距離被放得非常近,所以相鄰納米帶中的疇壁間的相互作用就變得非常重要。在本文中我們基于微磁模擬的方法首先研究了垂直各向異性對(duì)單條納米帶中電流驅(qū)動(dòng)渦旋疇壁運(yùn)動(dòng)的影響,然后分析了垂直各向異性對(duì)兩條納米帶中渦旋疇壁間耦合作用的影響。 第一章緒論部分主要介紹了磁性材料在計(jì)算機(jī)領(lǐng)域中應(yīng)用的發(fā)展,疇壁的相關(guān)知識(shí)以及疇壁運(yùn)動(dòng)方面已有的理論研究結(jié)果。第二章介紹了本論文工作所采用的微磁模擬方法——自旋動(dòng)力學(xué)模擬。 第三章詳細(xì)分析了包含自旋轉(zhuǎn)移力矩的顯式Landau-Lifshitz-Gilbert方程中每一項(xiàng)對(duì)電流驅(qū)動(dòng)渦旋疇壁運(yùn)動(dòng)的影響。并對(duì)渦旋中心橫向運(yùn)動(dòng)與渦旋中心和橫向壁部分的極化之間的關(guān)系進(jìn)行了分析。 在第四章中給出了不同垂直各向異性下電流驅(qū)動(dòng)疇壁運(yùn)動(dòng)的情況。研究顯示驅(qū)動(dòng)疇壁在水平方向和垂直方向運(yùn)動(dòng)的力隨著垂直各向異性和電流的增大而增大。然而,隨著垂直各向異性的增加,由束縛勢(shì)能引起的束縛力起初增加而后又減小。所以當(dāng)電流值較小時(shí),隨著垂直各向異性的增加,疇壁的水平速度先是減小而后又增加。而當(dāng)電流值較大時(shí),疇壁沿水平方向的速度隨垂直各向異性的增加單調(diào)增加。另一方面,疇壁橫向運(yùn)動(dòng)的速度隨垂直各向異性的增加而單調(diào)增加。在本章中還定量給出這些效應(yīng)背后的物理機(jī)制。 在最后一章中呈現(xiàn)了兩條納米帶中施加相反電流時(shí)耦合的兩渦旋疇壁間的振蕩行為。主要分析垂直各向異性對(duì)耦合疇壁間的振蕩行為的影響,結(jié)果顯示垂直各向異性可以改變耦合渦旋疇壁間的靜磁相互作用。
[Abstract]:Using polarization current to control domain wall motion in magnetic materials has important potential applications in the development of a new generation of solid-state data memory, logic devices and microwave devices. The domain wall motion caused by the spin transfer moment effect caused by free electrons has been fully studied theoretically and experimentally. At present, a major problem is that the current required to drive the continuous motion of domain walls is too large for practical applications. Recently, researchers have found that increasing vertical anisotropy in magnetic systems can enhance the motion of transverse domain walls. However, the corresponding physical mechanism has not been clearly explained. The vortex domain wall is a basic type of domain wall in the magnetic nanoscale system. The motion of vortex domain wall driven by current is more complicated than that of transverse domain wall because of the movement of vortex domain wall along the length of nanobelts and perpendicular to the direction of nanometer band. Theoretically speaking, the physical mechanism of vortex domain wall motion is more abundant than that of transverse domain wall. In addition, in high-density data memory design, the distance between nanowires and nanowires is very close, so the interaction between domain walls in adjacent nanowires becomes very important. In this paper, based on the method of micromagnetic simulation, we first study the effect of vertical anisotropy on the current driven vortex domain wall motion in a single nanocrystalline strip. Then the effect of vertical anisotropy on the coupling of vortex domain walls in two nanobelts is analyzed. The first chapter introduces the application of magnetic materials in the field of computer, the related knowledge of domain walls and the theoretical results of domain wall motion. In the second chapter, the micromagnetic simulation method, spin dynamics simulation, is introduced. In chapter 3, the effects of each term in the explicit Landau-Lifshitz-Gilbert equation including the spin transfer moment on the motion of the domain wall of the current-driven vortex are analyzed in detail. The relationship between the transverse motion of the vortex center and the polarization of the vortex center and the lateral wall is analyzed. In chapter 4, the motion of domain wall driven by current under different vertical anisotropy is given. It is shown that the force of driving domain wall moving in horizontal direction and vertical direction increases with the increase of vertical anisotropy and current. However, with the increase of vertical anisotropy, the binding force caused by binding potential energy increases at first and then decreases. So when the current value is small, the horizontal velocity of domain wall decreases and then increases with the increase of vertical anisotropy. When the current value is large, the velocity of domain wall along horizontal direction increases monotonously with the increase of vertical anisotropy. On the other hand, the velocity of transverse motion of domain wall increases monotonously with the increase of vertical anisotropy. The physical mechanisms behind these effects are also quantified in this chapter. In the last chapter, the oscillatory behavior between the two vortex walls coupled with the opposite current applied in the two nanoribbons is presented. The effect of vertical anisotropy on oscillatory behavior between coupled domain walls is analyzed. The results show that vertical anisotropy can change the magnetostatic interaction between coupled vortex walls.
【學(xué)位授予單位】：揚(yáng)州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM271

【共引文獻(xiàn)】

相關(guān)碩士學(xué)位論文 前1條

1 唐偉;調(diào)制納米線及納米電接觸的制備與表征[D];中南大學(xué);2013年

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本文編號(hào)：1827797