具有条纹畴结构磁性薄膜的高频微波磁性和磁化动力学及其机制研究

The high frequency permeability of stripe domain with rotatable anisotropy can be adjusted randomly in all directions of the film, which makes it more flexible in the application of microwave devices. However, some questions and challenges are still confused about their high frequency magnetic properties. In this project, the suitable resonance equation for the striped domain thin film is deduced and corrected by the experimental results and micromagnetics simulation. The dynamic hysteresis found in the magnetic spectra of the striped domain would show some relation with rotatable anisotropy, and the reason of the dynamic hysteresis would also be given. Based on the change of acoustic mode and optical mode, the results can realize controllable both high frequency and high permeability properties in the optical mode of the stripe domain thin film, and the physical mechanism of the optical mode is also revealed. In addition, the transforming reasons, physical mechanism and the magnetization dynamics between two modes are expounded by the experimental results and micromagnetics simulation in the situation when the directions of microwave field, magnetic field, and strip are changed respectively. As the results, it can provide the development for the future application of high frequency devices through this project by using the optical mode of strip domain with both high resonance frequency and high permeability, and also it can serve for the applications in the conversion of acoustic mode and optical mode, high- low frequency and multi-band frequency devices.

条纹畴具有的转动各向异性有利于高频磁导率随角度全方位调整，使它在微波器件应用中更加灵活，然而在其高频微波磁性的研究中还面临新的问题和挑战。本项目通过实验和微磁学模拟推导和修正适用于条纹畴薄膜模型的共振频率方程；通过条纹畴薄膜磁谱中发现的动态磁滞现象，研究其与转动各向异性的关系，揭示薄膜动态磁滞的原因；通过调控条纹畴光学模和声学模共振模式，实现条纹畴薄膜光学模式下高频率高磁导率调控，揭示光学模共振的物理增强机制；通过研究微波场、外加磁场和条纹方向不同位向关系下条纹畴薄膜声学模和光学模的共振变化规律，结合微磁学模拟揭示影响两种共振模式转换的因素，阐述其中的物理机制和磁化动力学过程。通过本项目研究，促进具有全方位转动同时具有高共振频率和高磁导率特性的光学模共振高频器件应用的发展，为实现铁磁共振声学模和光学模的转换优势以及高低频和多频段综合利用的器件提供依据。

条纹畴结构薄膜具有的周期性交替向上或向下偏离膜面排布的磁矩分布，使其表现出很多新颖且极具应用价值的动态磁特性，本项目主要以条纹畴结构软磁薄膜为研究对象，对条纹畴薄膜的条纹畴薄膜的图像、结构、基本磁性和高频磁性进行的系统研究。主要研究结果如下：.（1）薄膜厚增加会引起条纹畴结构增强和薄膜的垂直各向异性常数、品质因数和畴宽的增加。动态各向异性随着膜厚度或外加磁场的增加而减小，表明可旋转磁各向异性的面内磁化分量增加，而面外磁化分量减小，这导致膜厚增加时面外各向异性增强，面内各向异性减小。.（2）条纹畴中的自旋分布状态高度依赖于条带域的方向，高频微波磁特性被选择性地激发，出现了动态磁滞，声学模式，光学模式和垂直自旋驻波模式响应。.（3）薄膜的自旋分布从面内分布到条纹畴转变的过渡区域主要由自旋过渡涡旋和弯曲的条纹畴组成。过渡区域中非均匀自旋分布使磁谱线宽较宽但表现出更高的共振频率。具有明显条纹畴结构不利于提高样品声学模和光学模的共振频率。.（4）FeNi薄膜的bcc和bcc+fcc混合相显示出较小的晶粒尺寸和良好的磁滞回线矩形比以及明显的条纹畴图案，且具有良好的声学和光学模式共振磁特性，特别是当Ni原子的比例在25％-38％之间时，而且其对应的光学膜共振在较大的外磁场范围内共振仍可以保持。.（5）条纹畴薄膜加工成条带固定间隔3 μm，条带宽度为3-8 μm时，微纳加工对薄膜内的磁畴结构影响不大，薄膜依旧表现出条纹畴结构。但样品中声学模和光学模共振频率随微米条带宽度的减小而减小，其共振峰的吸收强度因样品中坡莫合金薄膜面积的减小而减弱。.（6）磁畴中的缺陷和钉扎会严重改变条纹畴的规则性和均匀性，从而降低了条纹畴薄膜的共振频率和强度，且较大钉扎会抑制了条纹畴薄膜共振以及自旋波的激发。.这些结果不仅有利于理解铁磁共振和自旋波在磁畴中的激发和共振，而且对条纹畴结构薄膜微波器件的开发很有帮助。.