兰州大学机构库 >物理科学与技术学院
利用磁力显微镜图像计算杂散场和分析磁畴结构
Alternative TitleCalculating stray field and analyzing magnetic domain structure by MFM image
尹格
Thesis Advisor白建民
2013-05-25
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword磁力显微镜 磁畴 杂散场 傅立叶变换
Abstract磁性材料的磁性与其精细磁畴结构有紧密的联系。因此,研究材料的磁畴结构对磁性纳米结构的磁性研究有重大的意义。磁力显微镜(MFM)是观察磁性材料表面微磁结构的重要仪器。但是MFM并不能对磁畴结构进行直接测量,而是测量得到磁性探针和样品表面的磁荷的相关作用。因此,发展和改进分析MFM图像的方法是有益于磁畴研究的。本文通过对磁性探针模型进行简化,从磁力显微镜的图像中计算得到了磁性薄膜样品的表面杂散场,并根据杂散场分布分析了样品的磁畴结构。 首先,MFM的图像可以认为是样品表面磁荷和探针的格林函数的卷积分,为计算方便,简化探针模型为一个点磁荷,通过去卷积的方法,就可以得到磁性样品表面的磁荷分布。样品表面上方空间的磁势满足Laplace方程,其中有一个边界条件与磁荷分布相关。利开离散傅立叶变换(DFT)的方法,可以求得磁势分布,对磁势分布求导,可以得到样品表面上方的杂散场分布。 之后,我们选取了厚度为 460 nm 的FeCoZr磁性薄膜样品的MFM图像,运用上面的方法计算出了杂散场。通过对杂散场分布的特征进行分析,我们认为有两种不同的磁矩分布方式可以产生这种特征的杂散场。其中一种是典型的Bloch 磁畴结构,另外一种是垂直磁各向异性导致的样品表面磁矩排列与样品表面成正弦分布的磁畴结构。结合样品的磁性和部分测量得到的样品参数,可以对这两种磁畴结构的能量值的估算,我们认为二者之中能量值较小的符合样品的实际磁畴结构,由此我们可以确定磁性薄膜样品的磁畴结构。 最后,我们计算了Co/Pd多层膜的比特图纹介质的杂散场分布并和理想比特图纹介质的杂散场分布进行了对比,发现两者符合得较好。
Other AbstractThere is larger correlation between the magnetic properties of the magnetic material and its fine magnetic domain structure, therefore, study the magnetic domain structure of materials have great significance in understanding magnetic properties of nanoscale magnetic material. The magnetic force microscopy (MFM) is an important instrument to observe the magnetic material surface micromagnetic structure. The MFM can not give the magnetic domain structure directly, but give the interaction between magnetic charges of the sample surface and magnetic probe. Therefore, the development and improvement of the methods of analysis of MFM images is beneficial to the study of the magnetic domains. Based on the simplified magnetic probe model, the surface of the stray field of the magnetic thin film sample can be calculated from the magnetic force microscopy image, and according to the distribution of the stray field the magnetic domain structure can be inferred and determined. First, the MFM image can be considered as the convolution of the MFM tip’s Green's function and the magnetic charge of the sample surface, for the convenience of calculation, a simplified probe model of a magnetic monopole type tip is effective in the deconvolution method, then we can obtain the magnetic charge distribution of the sample surface. The magnetic potential of the space above the sample surface satisfy the Laplace equation, which has a boundary condition with the distribution of magnetic charge. By using discrete Fourier transform (DFT) method, the magnetic potential distribution can be derived, and the stray field distribution of the sample surface is the gradient of magnetic potential distribution. After that, we select a MFM image of sample with a thickness of 460 nm FeCoZr thin film. Using the method above, the stray field of the sample can be calculated. By analyzing the characteristics of the stray field distribution, it’s believed that two different magnetic moment distributions can generate the stray field of such a feature. One kind of magnetic configuration is a typical Bloch magnetic domain structure, another is the sinusoidal distribution of magnetic moments resulting from the perpendicular magnetic anisotropy. Combining magnetic properties and other measured values of the sample, we can estimate the energy density value of the two kinds of the magnetic domain structure. It’s concluded that the smaller energy value of two is the actual magnetic domain structure o...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229620
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
尹格. 利用磁力显微镜图像计算杂散场和分析磁畴结构[D]. 兰州. 兰州大学,2013.
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