界面状态调控反常霍尔效应薄膜材料性能的研究

发布时间：2018-02-14 12:19

本文关键词： 磁性薄膜反常霍尔效应垂直磁各向异性热稳定性　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：自旋电子学是研究电子自旋相关输运过程及相应器件的一门新兴交叉学科,基于电子的电荷与自旋属性发展起来的自旋电子器件广泛应用在量子计算机、纳米逻辑器件、磁存储、卫星、个人电脑等先进领域。新型的自旋电子器件与传统的电子器件相比具有非易失性、高集成度、处理速度快、能耗低等显著优势,能够更好的满足未来电子器件微型化、集成化、智能化的需求。因此优化设计具备高性能的自旋电子材料就显得尤为重要。目前自旋电子材料广泛实用化还面临着一些问题：(1)作为存储器件的磁性薄膜材料要有良好的垂直磁各向异性；(2)输出信号要大：(3)同时做成器件时要与后续的半导体结构和工艺技术相兼容,材料需要经过350℃的退火处理过程,因此还要具有较好的热稳定性。本论文的研究工作就围绕这三个问题展开。由于之前研究者的工作主要是从界面的原子尺度和几何角度出发,如薄膜厚度以及界面的匹配程度、应力、缺陷、粗糙度、扩散等方面对磁性能及输运性能进行了研究,而更微观的界面状态的影响其实更为重要,需深入研究。因此,本论文通过引入催化剂、金属插层及氧化物覆盖层等手段制备了不同系列的多层膜材料,研究了界面状态对磁性及输运性能的影响,通过调控界面状态优化了多层膜的性能。丰要研究内容及成果如下：研究了过渡金属Ru的催化能力对MgO/CoFeB/Ta/MgO多层膜垂直磁各向异性的调控作用。我们发现催化剂Ru较强的氧储存／释放能力可以调控界面氧迁移使界面处原子获得适度的氧化,从而在无需退火制备态下就可以成功诱导MgO/CoFeB/Ta/MgO多层膜呈现良好的垂直磁各向异性。该研究成功利用催化剂促进了界面氧迁移,为调控自旋电子材料垂直磁各向异性提供了一种新的方法。研究了重金属元素Ru和轻金属元素Mg插入CoFeB多层膜体系后界面电子散射作用及其对反常霍尔效应的影响。结果发现,引入Mg后形成的MgO纳米颗粒弥散在界面处增加了杂质散射中心,对传导电子具有较强的漫散射作用,从而能够显著提高反常霍尔电阻率,而Ru引入后形成的金属／金属界面产生的散射中心较少,漫反射作用较弱,加之金属的分流作用反而较低了反常霍尔电阻率。研究了Fe／氧化物界面化学状态对于[Pt/Fe]_3多层膜反常霍尔输运性能的影响。我们发现在[Pt/Fe]_3氧化物覆盖层的异质结构中,Fe／氧化物界面的化学状态的变化对反常霍尔电阻率具有重要影响。当[Pt/Fe]_3多层膜上层覆盖MgO时,退火前反常霍尔电阻率变化350%,而上层覆盖物为SiO_2时,反常霍尔电阴率儿乎没有变化。通过XPS发现,MgO的引入使[Pt/Fe]_3多层膜的Fe/MgO界面处原子化学状态发生了明显的改变,从而导致了饱和磁化强度增大,这是其反常霍尔效应增强的丰要原因。研究了HfO_2覆盖层和Pt插层对Co/Ni多层膜垂直磁各向异性退火稳定性及其反常霉尔输运性能的影响。实验发现,引入HfO_2覆盖层后,Co/Ni多层膜的垂直磁各向异性的退火稳定性提高到了400℃,反常霍尔电阻率在375°时最高达到0.85μΩ·cm,与制备态相比提高了211%。同时发现随着Pt插层厚度的增加,有效磁各向异性能Keff随之增加。说明HfO_2覆盖层和Pt插层都能有效的提高Co/Ni体系的垂直磁各向异性性能。
[Abstract]:Spintronics is a new interdisciplinary research on electron spin transport process and corresponding devices, spin electronic devices developed in the electronic charge and spin properties based on extensive application in quantum computer, nanometer logic devices, magnetic storage, satellite, personal computer and other advanced fields. Electronic devices spin electronic devices with the traditional model compared with a non-volatile, high integration, fast processing speed, low power consumption advantages, can better meet the future miniaturization of electronic devices, integrated, intelligent demand. So the optimal design with high performance spintronic materials is particularly important. At present, the application of spintronic materials is also facing some question: (1) as the magnetic thin film memory device has good perpendicular magnetic anisotropy; (2) output signal to: (3) at the same time to do nothing and after The semiconductor structure and technology compatible materials need to be continued, after annealing process of 350 DEG C, and therefore also has good thermal stability. The research work of this thesis will focus on these three issues. Because of the researcher's work mainly from the perspective of the interface of the atomic scale and geometry, such as matching degree, thin film the thickness and interfacial stress, defects, roughness, diffusion and other aspects of the study on magnetic properties and transport properties, and the effect of the interface state of the micro is more important, need further study. Therefore, this paper through the introduction of catalyst, multilayer materials of different series of prepared metal intercalation and oxide coatings and other means, the interface of state transport properties of magnetic and, through the regulation of interface state to optimize the performance of multilayer film. The main research contents and results are as follows: Research on the transition of gold Regulation of Ru on the catalytic ability of MgO/CoFeB/Ta/MgO multilayer films with perpendicular magnetic anisotropy. We found that the catalyst Ru strong oxygen storage / release capacity can control the interface at the interface of atomic oxygen transfer to moderate oxidation, which is induced by power MgO/CoFeB/Ta/MgO multilayers exhibiting perpendicular magnetic anisotropy can be good without annealing preparation state. This study successfully used catalyst interface oxygen migration promoted, provides a new method for the manipulation of spin electronic materials perpendicular magnetic anisotropy. The effects of heavy metal elements Ru and light metal element Mg is inserted into the CoFeB multilayer system interface electron scattering and its effect on the anomalous Holzer effect. The results showed that MgO the nano particle dispersion is formed after the introduction of Mg increased the impurity scattering centers at the interface, has a strong role in the diffuse scattering of conduction electrons, which significantly To improve the anomalous Holzer resistivity, metal / metal interface and after the introduction of Ru to produce scattering center less diffuse reflection effect is weak, and the shunt metal has relatively low resistivity anomalous Holzer. Study on the chemical state of Fe / oxide interface transport properties for [Pt/Fe]_3 films. We found that the anomalous heterogeneous structure in Holzer [Pt/Fe]_3 oxide covering layer, changes in the chemical state of Fe / oxide interface has an important influence on Holzer. When the abnormal resistivity of [Pt/Fe]_3 multilayer upper cover MgO, annealing before the anomalous Holzer resistivity change 350%, while the upper cover is SiO_2, Holzer anomalous resistivity almost no change. Discovered by XPS the introduction of MgO, the Fe/MgO atom at the interface chemical state of [Pt/Fe]_3 multilayers changed significantly, which leads to the increase of saturation magnetization, which is abnormal The Holzer effect enhanced the main reason. On the HfO_2 layer and the Pt intercalation of Co/Ni multilayers with perpendicular anisotropy, annealing stability and abnormal mold transport performance. The experimental results showed that, the introduction of HfO_2 coating after annealing stable perpendicular magnetic anisotropy of Co/Ni multilayer film is increased to 400 DEG C, Holzer in 375 degrees when abnormal resistivity reaches 0.85 mu. Cm, and preparation of state higher than 211%. also found that with the increase of the Pt thickness, the effective magnetic anisotropy of Keff increased. HfO_2 layer and Pt layer are perpendicular magnetic anisotropy properties effectively improve Co/ Ni system.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.2

【参考文献】