磁力显微镜图像量化分析方法的研究

Quantification of nanoscale magnetic domains by MFM

磁力显微镜(magnetic force microscope,MFM)因测量不破坏样品、样品无需特别制备、以及纳米尺度的分辨率(10~50 nm)等优势,而广泛应用于各种磁性材料中磁畴结构的研究,尤其成为磁记录工业中研究磁介质和磁头的磁畴结构或磁场分布的有力工具.但是,标准MFM图像实际上是磁场力的二阶梯度图,而如何定量分析MFM图像、得到样品内部的磁矩分布信息,是近年来MFM研究领域迫切需要解决的问题,也是当前研究的热点.本文通过构筑精确的MFM成像理论发展一种磁力显微镜量化分析方法,为磁信息存储工业等重要领域关键技术的发展提供新型有力的工具.本文的关键在于构建MFM针尖的三维格林函数,通过格林函数方法解卷积MFM图像,获取样品中的有效磁荷结构.其次,建立和实际样品相符的微磁学模型,以有效磁荷驱动磁畴、畴壁的运动,构筑样品内部真实的磁畴结构,由此完成对MFM图像的量化解释.

The quantification of nanoscale magnetic domains in the area of magnetic force microscopy( MFM) has attracted great attentions due to its contributions to the development of next-generation products. MFM is well suited to exploring ferromagnetic domain structures. However,the quantification of magnetic domain structure cannot be achieved because the MFM signal only sensitive to the force gradients between tip and sample. Here,we develop a new method for quantifying the nanoscale magnetic domains,which is based on the basic principles of micromagnetics and deconvolution techniques. This method can locally quantify the magnetic domain structures in nanometer length scales. In this work,we use the MFM quantification method to locally observe and quantify the commercial SPT( single pole tip) head,hard magnetic thin films and polycrystalline LSMO films. Based on the theoretical analysis and experimental design,the quantification of magnetic field distributions and the evolution of magnetic domain structures have been demonstrated. The present method can be applied to investigate the microscopic magnetic domain structures in a variety of magnetic materials and devices,such as high-density recording media,recording and writing heads,ultrathin films,nanoparticles,patterned elements,as well as other magnetic features and nanostructures,which provides the possibility for directly observing the nanoscale magnetic features. It is a useful tool for the development of next-generation magnetic recording systems.