三种Fe基磁性薄膜的磁畴结构、磁各向异性及其高频性质的研究

发布时间：2018-09-06 10:55

【摘要】：磁各向异性是磁性薄膜最重要的基本特征之一,它的强度决定了磁性薄膜的自然共振频率。利用传统的调控方法产生一个方向确定的静态磁各向异性。若该薄膜用于高频磁性器件时则表现出明显的方向性,当微波磁场偏离磁各向异性的垂直方向时,器件则无法达到最佳性能。然而,利用条纹磁畴的转动磁各向异性可以解决高频电子器件方向性的问题。本论文研究了多晶NiFe磁性薄膜、非晶CoFeB磁性薄膜的制备工艺参数对条纹磁畴结构及其磁性能的影响规律。并为了满足电子器件柔性化的发展需求,利用具有超弹性的聚二甲基硅氧烷衬底结合倾斜溅射与衬底预应变研究了柔性褶皱薄膜的表面形貌、静态及动态磁性能。首先,通过磁控溅射生长多晶的NiFe磁性薄膜,系统地研究了NiFe薄膜的厚度、溅射功率密度、溅射气压等制备工艺参数对条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律。研究发现,高溅射功率密度可以降低薄膜出现条纹磁畴的临界厚度。NiFe薄膜的断面结构表明柱状晶的形成是表现出条纹磁畴结构的本质原因,高功率密度下低溅射气压有利于柱状晶结构的形成,表现出规整的条纹磁畴结构,高溅射气压会导致柱状晶纤细化,面内转动磁各向异性与面外垂直磁各向异性增强,条纹磁畴结构变得混乱。其次,利用倾斜磁控溅射的方法制备了非晶CoFeB磁性薄膜,并研究了通过改变倾斜溅射的角度对非晶CoFeB薄膜的磁畴结构、面内磁各向异性及其垂直磁各向异性的影响,并对非晶薄膜出现条纹磁畴结构的原因进行了分析。倾斜溅射可以诱导非晶的CoFeB薄膜出现条纹磁畴结构,并且随着倾斜角度的逐渐增大,薄膜的面内磁各向异性与垂直磁各向异性均呈现增加的趋势。通过对倾斜生长的薄膜进行断面结构分析,结果表明正是由于薄膜具有倾斜柱状结构的形状各向异性,从而导致薄膜的面内磁各向异性与垂直磁各向异性均显著增加。最终,利用具有超弹性的聚二甲基硅氧烷衬底研究了倾斜磁控溅射与衬底预应变对FeCoTa柔性褶皱薄膜的表面形貌、静态与动态磁性能的影响。在预拉伸的PDMS衬底上生长非磁性Ta释放拉伸后诱导形成表面呈现符合正弦函数的褶皱条纹结构。然后垂直于褶皱条纹方向倾斜溅射FeCoTa磁性薄膜,由于表面的褶皱条纹增强了倾斜溅射的自遮挡效应从而导致柔性磁性薄膜单轴各向异性和共振频率的增加。在柔性FeCoTa磁性薄膜中通过增大倾斜溅射角度与衬底预应变可以增强薄膜的单轴磁各向异性,从而致使薄膜的磁化机制偏向于畴壁形核。
[Abstract]:Magnetic anisotropy is one of the most important basic characteristics of magnetic thin films. Its intensity determines the natural resonance frequency of magnetic thin films. Traditional control methods are used to generate a directional static magnetic anisotropy. If the film is used in high frequency magnetic devices, it shows obvious directionality, and when the microwave magnetic field deviates from the vertical direction of magnetic anisotropy, the device can not achieve the optimal performance. However, the directional problem of high frequency electronic devices can be solved by using the rotational magnetic anisotropy of stripe domain. In this paper, the influence of the preparation process parameters of polycrystalline NiFe magnetic thin films and amorphous CoFeB magnetic thin films on the stripe domain structure and magnetic properties has been studied. In order to meet the development of flexibility of electronic devices, the surface morphology, static and dynamic magnetic properties of flexible pleated films were studied by using the superelastic polydimethylsiloxane substrate combined with slant sputtering and substrate pre-strain. Firstly, polycrystalline NiFe magnetic thin films were grown by magnetron sputtering. The thickness, sputtering power density and sputtering pressure of NiFe thin films were systematically studied to determine the stripe domain structure and in-plane static magnetic anisotropy. The effect of rotating magnetic anisotropy and vertical magnetic anisotropy in plane. It is found that high sputtering power density can decrease the critical thickness of stripe domain. The sectional structure of nife thin film shows that the columnar crystal formation is the essential reason for the stripe domain structure. Low sputtering pressure at high power density is favorable to the formation of columnar crystal structure, showing regular stripe domain structure. High sputtering pressure will result in the columnar crystal becoming fine, and the in-plane rotation magnetic anisotropy and the out-of-plane vertical magnetic anisotropy will be enhanced. The stripe domain structure becomes chaotic. Secondly, amorphous CoFeB magnetic thin films were prepared by inclined magnetron sputtering. The effects of the angle of tilt sputtering on the magnetic domain structure, in-plane magnetic anisotropy and perpendicular magnetic anisotropy of amorphous CoFeB films were studied. The reason of stripe domain structure in amorphous thin films was analyzed. Tilt sputtering can induce stripe domain structure in amorphous CoFeB films, and the in-plane magnetic anisotropy and vertical magnetic anisotropy of amorphous CoFeB films increase with the increasing of tilt angle. The results show that the in-plane magnetic anisotropy and perpendicular magnetic anisotropy of the films are significantly increased due to the shape anisotropy of the tilted columnar structure. Finally, the effects of inclined magnetron sputtering and substrate prestrain on the surface morphology, static and dynamic magnetic properties of FeCoTa flexible fold films were investigated by using polydimethylsiloxane substrates with hyperelastic properties. Non-magnetic Ta was grown on pre-stretched PDMS substrate, and the surface was induced to form a fold stripe structure with a sinusoidal function after releasing and stretching. Then inclined sputtering FeCoTa magnetic thin films perpendicular to the direction of fold stripes. Due to the enhancement of the self-occlusion effect of slanting sputtering the uniaxial anisotropy and resonance frequency of the flexible magnetic thin films are increased due to the wrinkle stripes on the surface. The uniaxial magnetic anisotropy of flexible FeCoTa films can be enhanced by increasing the angle of oblique sputtering and the substrate prestrain, which results in the magnetization mechanism of the films being biased towards the domain wall nucleation.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2

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