铁镍合金薄膜中的自旋驻波研究

发布时间：2018-03-19 13:48

本文选题：自旋驻波　切入点：自旋整流　出处：《兰州大学》2015年硕士论文　论文类型：学位论文

【摘要】：LLG方程是描述磁性材料动态特性的理论基础,通常独立用于研究磁性材料的共振问题。然而,当铁磁金属薄膜中激发出自旋驻波时,磁矩的非一致进动会使得磁矩之间的交换作用等效场具有空间旋度,并随时间变化。此时,除了LLG方程之外,还需要额外考虑交换作用等效场的电磁效应。根据麦克斯韦方程组,磁场的空间旋度对应着传导电流,而时变的磁场会在空间中产生涡旋电场。因此,自旋驻波的交换作用等效场必然会在铁磁金属薄膜中产生振荡的电流,进而强烈地影响微波在铁磁金属薄膜中的传播。本文首先从麦克斯韦方程组出发,理论预言了这一电流的存在。考虑到铁磁金属薄膜中,电流分布的复杂性,本文继而采用自旋整流技术对这种电流进行探测。从实验结果中,我们发现了两个有力的证据：1.自旋驻波自旋整流信号的线型,始终表现为Dispersion线型；相比之下,铁磁共振的自旋整流信号则是Dispersion和Lorenz两种线型的混合线型。2.自旋驻波自旋整流信号随外加磁场的空间角度依赖关系,明显区别于铁磁共振。从这两条实验结果出发,本文利用LLG方程和麦克斯韦方程组,详细论证了上述电流的存在。紧接着这一工作,本文另外设计了一个利用ESR谱仪探究坡莫合金薄膜中自旋驻波的实验。从实验结果可以看出,不同于铁磁共振,自旋驻波会对TE011谐振腔中的微波分布产生剧烈地影响。本文认为这是由坡莫合金中自旋驻波激发的面内涡流导致的。这一结果是对自旋整流实验结果的补充,也进一步证明了,自旋驻波会在磁性金属薄膜中激发出振荡电流这一假说。
[Abstract]:The LLG equation is the theoretical basis for describing the dynamic characteristics of magnetic materials and is usually used independently to study resonance problems of magnetic materials. However, when self-rotating standing waves are excited in ferromagnetic metal thin films, The nonuniform precession of magnetic moment will make the equivalent field of exchange between magnetic moments have spatial curl and change with time. In this case, except for LLG equation, According to Maxwell's equations, the space curl of the magnetic field corresponds to the conduction current, while the time-varying magnetic field produces a vortex electric field in space. The equivalent field of spin standing wave exchange will inevitably produce oscillatory current in ferromagnetic metal film, which will strongly affect the propagation of microwave in ferromagnetic metal film. The existence of the current is predicted theoretically. Considering the complexity of the current distribution in ferromagnetic metal films, the spin rectifier technique is used to detect the current. We found two compelling evidence: 1. The lines of the spin standing wave spin rectifier signal always behave as Dispersion lines; in contrast, The spin rectifier signal of ferromagnetic resonance is a mixed linear type of Dispersion and Lorenz. 2. The spin rectifier signal of spin standing wave depends on the spatial angle of the applied magnetic field, which is obviously different from that of ferromagnetic resonance. In this paper, the existence of the above current is demonstrated in detail by using the LLG equation and Maxwell equation. In addition, an experiment was designed to investigate the spin standing waves in permalloy films by ESR spectrometer. The experimental results show that it is different from ferromagnetic resonance. The spin standing wave will have a severe effect on the microwave distribution in the TE011 resonator. It is believed that this is caused by the in-plane eddy current excited by the spin standing wave in permalloy. This result complements the experimental results of spin rectifier and further proves that, The hypothesis that a spin standing wave excites an oscillating current in a magnetic metal film.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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