界面电子结构对纳米多层膜磁性的影响研究

发布时间：2018-01-26 04:56

本文关键词： 纳米磁性多层膜金属/氧化物界面界面电子结构垂直磁各向异性界面磁各向异性　出处：《北京科技大学》2015年博士论文　论文类型：学位论文

【摘要】：随着纳米尺度材料的发展,与尺寸、维度息息相关的表面、界面效应的研究一直是相关领域的热点。其中,由铁磁和反铁磁与非磁金属或氧化物界面组成的异质结纳米多层膜具有高的热稳定、高的磁电阻效应、高的磁光克尔效应、低的电流驱动磁化翻转电流密度以及易与半导体工艺兼容等优点,是自旋电子学领域的核心材料。有研究表明,薄膜厚度以及界面的匹配程度、应力、缺陷、粗糙度、扩散等对铁磁层和反铁磁层的磁性能(比如磁化强度、矫顽力、磁各向异性、磁阻尼和交换偏置效应等)都有重要影响。然而,前人的工作主要是从界面的原子尺度和几何角度出发,而更微观的界面电子结构比如界面处不同原子之间成键、电了轨道杂化等等对纳米多层膜磁性的影响更为重要,需深入研究。因此,本论文在自旋电子学领域具有广泛应用前景的纳米磁性多层膜中,通过插层等于段制备了不同系列的多层膜材料,研究了界面电子结构对磁性的影响,并通过调控界面的电子结构改善了多层膜的磁性能。本论文的主要研究内容如下(1)在Ta/CoFeB/MgO/Ta多层膜的CoFeB/MgO界面引入极微量的Fe原子,随着Fe原子的增加,CoFeB/MgO界面附近依次出现FeOx(x1)、Fe2O3和Fe304等Fe的化合物,说明微量Fe的引入调控了CoFeB/MgO界面的电子结构;同时,由于不同Fe氧化物中Fe-O键距离的不同,改变了界面处Fe 3d-O印轨道杂化的程度,导致多层膜的磁各向异性也出现了相应的变化。另外,Fe的引入还可以降低多层膜的有效磁阻尼(2)研究了IrMn/MgO界面引入超薄Mg层对具有隧穿各向异性磁电阻结构的Pt/NiFe/IrMn/MgO/Pt多层膜磁性的影响。研究发现Mg层的引入可以显著抑制IrMn/MgO界面处Mn-O键的形成,使多层膜的Blocking温度从远低于室温提高到了室温以上,同时交换偏置效应也获得了显著提高。另外,Mg层的引入还能促进高质量MgO(200)织构的生成。该研究对获得室温下应用的基于反铁磁的自旋电子器件具有重要意义。(3)研究了Co/Pt多层膜不同界面掺杂Fe原子对垂直磁各向异性的影响。实验结果表明当Fe原子掺杂在Pt/Co界面时可以同时提高多层膜的垂直磁各向异性及其退火稳定性。我们认为垂直磁各向异性的增强主要是由Fe引入后优化了Pt/Co界面的电子结构所致。(4)研究了Pt插层对Co/Ni多层膜垂直磁各向异性及其退火稳定性的影响。实验发现,随着Pt插层厚度的增加,Co/Ni多层膜的垂直磁各向异性获得显著增强。同时,引入0.6 m的Pt后,垂直磁各向异性的退火稳定性从没有Pt插层的350℃提高到了480℃。分析认为,Pt插层的引入增强了界面电子轨道的杂化效应,同时引入的Pt具有(200)取向,导致垂直磁各向异性及其退火稳定性的提高。(5)研究了界面氧迁移对Pt/Co/MgO/Pt和Pt/Co/SiO2/Pt多层膜磁性的影响。实验结果表明在薄膜制备和后续退火的过程中,Co/MgO界面和Co/Si02界面存在氧原子的迁移,氧原子通过与Co的氧化还原反应来实现其迁移过程。界面氧迁移不但可以使界面处获得有益的Co 3d-O 2p轨道杂化,还可以改善界面的结晶质量,使多层膜出现面内磁各向异性向垂直磁各向异性的转变。该研究表明界面氧迁移是一种普遍存在于铁磁/氧化物界面的现象,对纳米多层膜材料的磁性能具有重要影响。
[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.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O484.43;TB383.1

【共引文献】