Near-field Magneto-optical Microscope for Observation of Nano-spin Structure

本文介绍了在文部科学研究助学金(批准号：07555099)的支持下研制的扫描近场磁光显微镜。近年来，纳米制造技术的快速发展导致了亚微米结构磁性材料的实现，这就要求亚微米到纳米区域的观察技术的发展。人们已经研究了各种观察技术，如磁力显微镜(MFM)、电子束全息术(EBH)和自旋极化扫描电子显微镜(SPSEM)。虽然磁力显微镜和电子轰击能提供关于磁性材料周围磁场的丰富信息，但它们不能直接给出样品的磁化强度信息。表面扫描电子显微镜是一种直接观察表面自旋极化的优秀技术，但要想进行…，还需要进行大量的基础研究由于它对样品的表面条件过于敏感，因此将其作为一种通用的测量技术。与这些类型的显微镜相比，扫描近场光学显微镜(SNOM)可以直接提供材料本身的磁化信息。首先，我们关注了弯曲光纤探头中的偏振传输特性，在我们所采用的系统中，弯曲光纤探头同时作为AFM的悬臂。研究发现，仔细选择光纤探头和优化补偿光学元件可以提供良好的偏振特性。利用优化后的光纤探头，在交叉偏振器配置下，成功地观测到了含镝铁石榴石薄膜的磁光光盘上记录标记的磁光图像。其次，为了提高磁光信号的灵敏度，我们引入了利用光弹调制器(PEM)的偏振调制技术。我们成功地在亚微米长的铂/钴圆盘上获得了人字形的痕迹。利用聚焦离子束(FIB)技术制备了亚微米尺寸的钴微结构。我们获得了微结构的磁光图像。结果表明，该微结构可以作为磁光近场光学显微镜的标准图形。较少

This report describes the research and development of a scanning near-field magneto-optical microscope conducted under the support of Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture (Category No.07555099).Recently the rapid development in the nano-fabrication technique has lead to the realization of magnetic materials with a sub micron structure, which requires development of observation technology for the Sub-micron to nanometer region. There have been studied various observation techniques such as the magnetic force microscopy (MFM), the electron beam holography (EBH), and the spin-polarized scanning electron microscope (SPSEM). Although MFM and EBH provide ample information on the magnetic field around the magnetic materials, they do not give information of the sample magnetization directly.SPSEM is an excellent technique to observe the spin polarization of the surface directly, it still requires much fundamental studies in order to g … More et a position as a versatile measuring technique, since it is too sesitive to the surface condition of the sample. Compared with these sorts of microscopy the scanning near-field optical microscopy (SNOM) can provide direct information of the magnetization in the material itself.First we took attention on the polarization transmission properties in the bent-fiber probe, which simultaneously work as a cantilever for AFM in the system we employed. It is found that careful selection of the fiber-probe and optimization of the compensating optics can provide a good polarization characteristics. Using the fiber probe with optimized optics we successfully observed magneto-optical-images of the recorded marks on a MO disc with the dysprosium iron garnet film under the crosspolarizer configuration.Next in order to increase sensitivity of the magneto-optical signal we introduced the polarization-modulation technique using the photoelastic modulator (PEM). We successfully obtained the chevron-shaped marks on the platinum/cobalt disk with submicron length. The resolution attained was 90nm.We prepared microstructures of cobalt with sub-mirometer size using focused ion beam (FIB) technology. We obtained magneto-optical images of the microstructure. It is confirmed that the microstructure can be used as a standard pattern for the magneto-optical SNOM. Less