多物理场下多层膜结构的自旋相关输运性质的研究

发布时间：2018-06-05 16:03

  本文选题：多层膜 + 反常能斯特效应　； 参考：《中国科学院大学(中国科学院物理研究所)》2017年硕士论文

【摘要】：含有铁磁层/非铁磁层界面的多层膜体系一直以来作为自旋电子学的重要研究对象,可以提供多种特别的物理性质,如空间对称性破缺、垂直磁各向异性,从而为电流翻转磁矩、高密度存储等多种具有巨大应用价值的器件功能的实现提供了可靠的物理基础。因此,对多层膜结构的输运特性的研究,特别是输运性质对多种物理场的响应特征及其内在机制的阐明,可为今后材料开发和器件应用提供诸多借鉴。就此方面问题,本文主要阐述以下两方面工作:(1)通过磁控溅射生长铂/钴多层膜,并加工为反常能斯特或反常霍尔效应的测量结构。通过电学输运测量来表征体系中两个效应的特征量——反常霍尔角和反常能斯特系数,讨论二者随着铁磁/非磁界面数量增多的变化,以及二者之间的依赖关系。同时基于线性响应理论,通过已有的唯象输运模型来推导出二者间的关系式,并与实验得到的结果作比较。综合模型及实验结果,得出二者存在着线性的正相关性,以及都随着界面数量增多引起的体系自旋轨道耦合增强而增长的结论。(2)磁控溅射生长的铁磁/氧化物势垒/重金属结构经过退火工艺诱导出面内易磁化轴。经微加工制备出具有一个顶电极和三个底电极的隧道结样品。通过加载电流于结区,实现自旋极化电流从铁磁层注入重金属层。注入的自旋可通过逆自旋霍尔效应在两个底电极之间探测到。另外,采用三端法加载交流电流测量结区电阻随垂直膜面磁场变化引起的汉勒效应,得到结区电阻的磁场依赖特性,进行拟合得到重金属铂和钽中的自旋弛豫时间。进一步结合电阻率的温度依赖关系,推测出铂中的自旋弛豫机制来自于E-Y机制。
[Abstract]:The multilayer system with ferromagnetic / non-ferromagnetic layer interface has been an important research object of spin electronics, which can provide a variety of special physical properties, such as space symmetry breaking, vertical magnetic anisotropy. This provides a reliable physical basis for the realization of the functions of many devices with great application value, such as current-flipping magnetic moment, high-density storage and so on. Therefore, the study of the transport characteristics of multilayer membrane structures, especially the response characteristics of transport properties to various physical fields and the elucidation of their internal mechanisms, can provide many references for the development of materials and the application of devices in the future. In this respect, this paper mainly describes the following two aspects of work: 1) growth of platinum / cobalt multilayers by magnetron sputtering and fabrication into anomalous Nernst or anomalous Hall effect measurement structures. The anomalous Hall angle and anomalous Nernst coefficient of the two effects in the system are characterized by electrical transport measurements. The variation of the two effects with the increase of the number of ferromagnetic / non-magnetic interfaces and their dependence are discussed. At the same time, based on the linear response theory, the relationship between the two is derived through the existing phenomenological transport model, and compared with the experimental results. By synthesizing the model and the experimental results, it is concluded that there is a positive linear correlation between the two models. The results show that the ferromagnetic / oxide barrier / heavy metal structure grown by magnetron sputtering is induced by annealing process to induce the internal magnetization axis. Tunnel junction samples with one top electrode and three bottom electrodes were fabricated by microfabrication. The spin-polarization current is injected into the heavy metal layer from the ferromagnetic layer by loading the current in the junction region. The injected spin can be detected by inverse spin Hall effect between two bottom electrodes. In addition, a three-terminal method is applied to measure the Hansel effect caused by the variation of the junction resistance with the magnetic field of the vertical film surface. The magnetic field dependence of the junction resistance is obtained, and the spin relaxation time in the heavy metal platinum and tantalum is obtained by fitting. Combining the temperature dependence of resistivity, it is inferred that the spin relaxation mechanism in platinum comes from the E-Y mechanism.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2
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本文编号：1982564