矩形单元面内自旋波激发的微磁学模拟研究

论文总字数：40843字

摘 要

Kittel于1958年首先提出了自旋波共振的概念，他指出在一定的边界条件下，在处于均匀交变磁场中的磁性薄膜上可以观察到自旋波共振的现象。同年，便有科研工作者在磁性薄膜中首次观察到自旋波共振谱，从此以后，薄膜的自旋波共振研究引起了科研工作者的广泛的兴趣。科研工作者们竞相用不同的材料进行实验，不断地改进实验的方法，对所得结果进行理论探讨。自旋波共振已经成为了研究磁性材料的内禀性质的一种有效手段。铁镍薄膜的自旋共振是研究得最多的也是最早的，七十年代以来科研工作者们相继对YIG单晶薄膜和非晶态薄膜的自旋波共振也进行了研究。研究自旋波的实验方法是利用自旋波与其他物理现象或因素的相互作用，例如磁共振方法、光散射方法和中子散射方法等。自旋波除了热激发外，还有其他的激发方法。例如，在铁磁共振中，在均匀恒定磁场作用下，利用均匀的高频磁场可激发k=0的自旋波(即一致进动)，亦可在薄膜中激发一定波数的自旋波驻波，称为自旋波共振；利用非均匀的高频磁场可激发k0的自旋波(即非一致进动)，大的自旋波称为交换波；小的自旋波称为静磁波；当很小以至其波长与样品线度相当时称为静磁模。在高功率铁磁共振中，当微波功率超过某临界值时，由于一致进动与自旋波的耦合，某种自旋波可被激发。此外利用光子或中子与磁振子的非弹性散射也可激发自旋波。由于实验条件的限制，实验制得的薄膜难免会有结构上以及成分上的缺陷，薄膜的尺寸大小也很难进行控制。后来随着计算机的发展以及计算机模拟计算的成熟，使得科研工作者可以在计算机上对薄膜上的自旋波进行模拟研究。

本文首先研究了在单层矩形单元薄膜上自旋波的激发、共振频谱以及空间分布情况，包括矩形单元的大小以及矩形比对自旋波的影响情况，随后研究了自旋波在双层膜矩形单元上的传播情况，最后，本文研究了多个矩形单元不同组合情况下（分为“头对尾”、“肩対肩”两种组合情况）单元间相互作用对自旋波的影响情况。

关键词：矩形单元，自旋波激发，自旋波共振，微磁学模拟

ABSTRACT

Kittel first put forward the concept of spin-wave resonance in 1958. He pointed out that, under certain boundary conditions, the phenomenon of spin-wave resonance could be observed on magnetic films in uniform alternating magnetic fields. In the same year, researchers first observed the spin-wave resonance spectrum in magnetic thin films. Since then, the study of spin wave resonance of thin films has aroused wide interest of researchers. Researchers are competing to conduct experiments with different materials, constantly improving the methods of experiments, and making theoretical discussions on the results obtained. Spin-wave resonance has become an effective means to study the intrinsic character of magnetic materials. Spin-wave resonance of Ni-Fe film the is more than just the first to be studied, but also the most frequent to be studied , since the 1970s, scientific research workers have studied spin wave resonance of the YIG crystal film and of the amorphous film. The experimental method of studying the spin wave is to use the interaction between the spin wave and other physical phenomena or factors, such as magnetic resonance method, light scattering method and neutron scattering method.  

In addition to thermal excitation, there are other methods of to excite the spin wave. For example, considering the ferromagnetic resonance, under the influence of uniform constant magnetic field, uniform high-frequency magnetic field can excite spin wave with k = 0 (that is, uniform precession), can excite spin standing wave with a certain wave number, which is called spin-wave resonance; The non-uniform high frequency magnetic field can excite spin wave with k 0 (non-uniform precession). Long-wavelength spin wave is called exchange wave. Short-wavelength spin wave is called magnetostatic wave. It is called magnetostatic mode when its wavelength is so short that it is almost the same as that of the sample. In high-power ferromagnetic resonance, when the microwave power exceeds a certain critical value, due to the coupling of uniform precession and spin wave, some kind of spin wave can be excited. In addition, the inelastic scattering by photons or neutrons and magnetic oscillators can also excite the spin wave. Due to the limitation of experimental conditions, the experimental film will inevitably have structural and component defects, and the size of the film is difficult to control. Nowdays, with the development of computers and the improvement of practicability

of computer simulation, researchers are able to simulate the spin waves on thin films on computers.

At first, I study spin wave excitation on the single-layer film and spin-wave resonance spectrum, then I study the influence of squareness ratio and the size of the film on the spin wave, at the same time, I study the spread of the spin wave on two-layer film. In the end, I study the influence of the relative location of the films (" head to tail ", "shoulder to shoulder") on the spin wave.

KEY WORDS: RECTANGLE ELEMENT, SPIN-WAVE RESONANCE, MICROMAGNETIC SIMULATION, SPIN-WAVE EXCITATION

目 录

摘 要 I

ABSTRACT II

绪 论 1

第一章 单层Ni₈₀Fe₂₀矩形单元薄膜中的自旋波 11

1.1 固定尺寸的单层Ni₈₀Fe₂₀矩形单元的自旋波激发 11

1.1.1 模型和参数设置 11

1.1.2 微磁学模拟过程 11

1.1.3模拟实验结果以及分析 12

1.2 Ni₈₀Fe₂₀矩形单元的矩形比对自旋波激发的影响 13

1.2.1 模型和参数设置 13

1.2.2 模拟实验结果以及分析 14

1.3 Ni₈₀Fe₂₀矩形单元的尺寸对自旋波激发的影响 15

1.3.1 模型和参数设置 15

1.3.2 模拟实验结果以及分析 15

1.4 双层Ni₈₀Fe₂₀矩形单元上的自旋波 16

1.4.1 模型和参数设置 16

1.4.2 模拟实验结果以及分析 17

第二章 单元间相互作用对Ni₈₀Fe₂₀矩形单元中自旋波的影响 19

2.1 矩形单元的间隔对自旋波激发的影响 19

2.1.1 模型和参数设置 19

2.1.2 模拟实验结果以及分析 20

致 谢 25

参考文献 26

附录 A 30

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