本文關鍵詞： 納米磁性多層膜 金屬/氧化物界面 界面電子結構 垂直磁各向異性 界面磁各向異性　出處：《北京科技大學》2015年博士論文　論文類型：學位論文

【摘要】：隨著納米尺度材料的發(fā)展,與尺寸、維度息息相關的表面、界面效應的研究一直是相關領域的熱點。其中,由鐵磁和反鐵磁與非磁金屬或氧化物界面組成的異質結納米多層膜具有高的熱穩(wěn)定、高的磁電阻效應、高的磁光克爾效應、低的電流驅動磁化翻轉電流密度以及易與半導體工藝兼容等優(yōu)點,是自旋電子學領域的核心材料。有研究表明,薄膜厚度以及界面的匹配程度、應力、缺陷、粗糙度、擴散等對鐵磁層和反鐵磁層的磁性能(比如磁化強度、矯頑力、磁各向異性、磁阻尼和交換偏置效應等)都有重要影響。然而,前人的工作主要是從界面的原子尺度和幾何角度出發(fā),而更微觀的界面電子結構比如界面處不同原子之間成鍵、電了軌道雜化等等對納米多層膜磁性的影響更為重要,需深入研究。因此,本論文在自旋電子學領域具有廣泛應用前景的納米磁性多層膜中,通過插層等于段制備了不同系列的多層膜材料,研究了界面電子結構對磁性的影響,并通過調控界面的電子結構改善了多層膜的磁性能。本論文的主要研究內容如下(1)在Ta/CoFeB/MgO/Ta多層膜的CoFeB/MgO界面引入極微量的Fe原子,隨著Fe原子的增加,CoFeB/MgO界面附近依次出現(xiàn)FeOx(x1)、Fe2O3和Fe304等Fe的化合物,說明微量Fe的引入調控了CoFeB/MgO界面的電子結構;同時,由于不同F(xiàn)e氧化物中Fe-O鍵距離的不同,改變了界面處Fe 3d-O印軌道雜化的程度,導致多層膜的磁各向異性也出現(xiàn)了相應的變化。另外,Fe的引入還可以降低多層膜的有效磁阻尼(2)研究了IrMn/MgO界面引入超薄Mg層對具有隧穿各向異性磁電阻結構的Pt/NiFe/IrMn/MgO/Pt多層膜磁性的影響。研究發(fā)現(xiàn)Mg層的引入可以顯著抑制IrMn/MgO界面處Mn-O鍵的形成,使多層膜的Blocking溫度從遠低于室溫提高到了室溫以上,同時交換偏置效應也獲得了顯著提高。另外,Mg層的引入還能促進高質量MgO(200)織構的生成。該研究對獲得室溫下應用的基于反鐵磁的自旋電子器件具有重要意義。(3)研究了Co/Pt多層膜不同界面摻雜Fe原子對垂直磁各向異性的影響。實驗結果表明當Fe原子摻雜在Pt/Co界面時可以同時提高多層膜的垂直磁各向異性及其退火穩(wěn)定性。我們認為垂直磁各向異性的增強主要是由Fe引入后優(yōu)化了Pt/Co界面的電子結構所致。(4)研究了Pt插層對Co/Ni多層膜垂直磁各向異性及其退火穩(wěn)定性的影響。實驗發(fā)現(xiàn),隨著Pt插層厚度的增加,Co/Ni多層膜的垂直磁各向異性獲得顯著增強。同時,引入0.6 m的Pt后,垂直磁各向異性的退火穩(wěn)定性從沒有Pt插層的350℃提高到了480℃。分析認為,Pt插層的引入增強了界面電子軌道的雜化效應,同時引入的Pt具有(200)取向,導致垂直磁各向異性及其退火穩(wěn)定性的提高。(5)研究了界面氧遷移對Pt/Co/MgO/Pt和Pt/Co/SiO2/Pt多層膜磁性的影響。實驗結果表明在薄膜制備和后續(xù)退火的過程中,Co/MgO界面和Co/Si02界面存在氧原子的遷移,氧原子通過與Co的氧化還原反應來實現(xiàn)其遷移過程。界面氧遷移不但可以使界面處獲得有益的Co 3d-O 2p軌道雜化,還可以改善界面的結晶質量,使多層膜出現(xiàn)面內磁各向異性向垂直磁各向異性的轉變。該研究表明界面氧遷移是一種普遍存在于鐵磁/氧化物界面的現(xiàn)象,對納米多層膜材料的磁性能具有重要影響。
[Abstract]:With the development of nano scale materials and size, surface dimensions are closely related to the research, the interface effect is always the hot topic in related fields. Among them, composed of ferromagnetic and anti ferromagnetic and nonmagnetic metal or oxide interface heterojunction nano multilayer film has high thermal stability, high magnetoresistance, magnetic optical Kerr the effect of high and low current driven magnetization reversal current density and easily compatible with semiconductor technology and other advantages, is the core material in spintronics. Studies have shown that the matching degree, film thickness and interfacial stress, defects, roughness, diffusion of magnetic ferromagnetic layer and antiferromagnetic layer can (such as magnetization, coercivity, magnetic anisotropy, magnetic damping and exchange bias effect) have a significant impact. However, previous work mainly from the perspective of the interface of the atomic scale and geometry, and the micro interface electronic structure For example, the interface between different atomic orbitals, the effect of hybridization on electric magnetic nano multilayer film is more important and needs further study. Therefore, the nano magnetic multilayer film has wide application prospect in the field of spintronics, the intercalation is equal to the multilayer materials of different series were prepared for study. The effect of interface on the electronic structure of magnetic and electronic structure, through the control interface to improve the magnetic multilayer film. The main research contents of this thesis are as follows (1) the introduction of trace amount of Fe atoms in the Ta/CoFeB/MgO/Ta multilayer CoFeB/MgO interface, with the increase of Fe atom, CoFeB/MgO near the interface there are FeOx (x1). Fe304 compounds Fe2O3 and Fe, indicating that the introduction of Fe micro regulation of the electronic structure of CoFeB/MgO interface; at the same time, because of the different Fe-O bond Fe oxides in different distance, change at the interface of Fe 3d-O India The extent of hybridization, resulting in magnetic anisotropy of multilayers have changed accordingly. In addition, the effective magnetic damping can also reduce the introduction of Fe multilayer film (2) on the IrMn/MgO interface into ultrathin Mg layer with Pt/NiFe/IrMn/MgO /Pt multilayer magnetic tunneling anisotropic magnetoresistance effect. The study found that the structure of the formation of the introduction of Mg layer can significantly inhibit IrMn/MgO at the interface of the Mn-O key, the multilayer Blocking temperature from far below the ambient temperature is increased to above room temperature, the exchange bias effect is remarkably improved. In addition, the introduction of Mg layer can also promote the high quality of MgO (200) texture formation. The study of application room temperature spintronic devices based on antiferromagnetic has important significance. (3) studied the effect of Co/Pt multilayer films with different interface doping Fe atom of perpendicular magnetic anisotropy. The experiment results show that when Fe atoms doped In the complex Pt/Co interface can also improve the perpendicular magnetic anisotropy and annealing stability of multilayer films. We believe that the enhancement of the perpendicular magnetic anisotropy is mainly introduced by Fe after optimization of the electronic structure caused by Pt/Co interface. (4) studied the Pt intercalation of Co/Ni multilayer perpendicular magnetic anisotropy and the annealing effect on the stability of the. The experimental results revealed that with increasing Pt layer, perpendicular magnetic anisotropy of Co/Ni multilayers was significantly enhanced. At the same time, the introduction of 0.6 m Pt after annealing, the stability of perpendicular magnetic anisotropy from no Pt intercalated 350 degrees up to 480 DEG C. Analysts believe that the introduction of Pt intercalation was enhanced hybrid effect interface electronic track, while the introduction of Pt with (200) orientation, resulting in perpendicular magnetic anisotropy and its annealing stability improved. (5) the interface of oxygen transfer effect on magnetic Pt/Co/MgO/Pt and Pt/Co/SiO2/Pt multilayers. The experimental results show that in the process of film preparation and subsequent annealing in the migration of Co/MgO interface and the Co/Si02 interface are oxygen atoms, oxygen atoms by reduction reaction with the oxidation of Co to realize the interface migration process. It can not only make the oxygen transfer at the interface of Co 3d-O 2p orbitalhybridization beneficial, but also can improve the crystal quality of the interface the multilayer film changes, in-plane magnetic anisotropy to perpendicular magnetic anisotropy. The study shows that interface oxygen transfer is a universal phenomenon existing in the ferromagnetic / oxide interface, magnetic properties of nano multilayer materials has important influence.

【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：O484.43;TB383.1

【共引文獻】

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本文編號：1464734