Fundamental Study on magnetic-granular films with fine structures

本研究的主题是制备磁性颗粒薄膜的精细结构。磁性颗粒膜被认为是一种新型的磁性物质。具体地说，它的目标是在非晶态薄膜中产生小于几十纳米的细小磁性颗粒区。到目前为止，还没有一种方法可以确定在如此小的区域内的磁态。因此，我们首先要实现对小于10 nm的细小颗粒磁性的观测。为了制作颗粒区的图案，要求原始基质为非晶态或直径小于1 nm的超细晶多晶。I)我们找到了用直流磁控溅射方法制备Fe_8Mo_2非晶膜的条件。ii)利用配备场发射电子枪和磁屏蔽电子透镜的透射式电子显微镜，我们成功地观察到了Fe颗粒嵌在氧化镁单晶中和Fe颗粒在Fe_8Mo_2非晶薄膜中析出的情况下，小于10 nm的具有单一磁畴的细小颗粒的磁性状态。非晶态薄膜中弥漫着宽度小于100 nm的颗粒区“N”字样。用Lorentz显微镜观察到该区域内的一些颗粒具有自磁化现象，小区X射线分析证实这些颗粒中的Fe原子浓度大于80%。

The theme of this research is to make fine structures of magnetic granular thin films. Magnetic granular films have been remarked as one of new magnetic substances. Specifically, it has been aimed to produce fine magnetic-granular areas less than a few tens nanometers in an amorphous thin film. No method to investigate the magnetic state in such small region bad been confirmed, so far. Therefore, first of all, we had to realized the observation of the magnetism of fine particles less than 10 nm. In order to make a pattern of granular area, the original matrix is required to be amorphous or a poly-crystal of ultra fine grains less than 1 nm in diameter.Following results have been obtained in this project ;i) We have found the condition to make an amorphous film of Fe_8Mo_2 using a DC magnetron sputtering method.ii) By Lorentz electron microscopy using a transmission electron microscope instrument equipped with a field emission electron gun and a magnetically shielded electron lens, we observed successfully the magnetic states of fine particles less than 10 nm which have single magnetic domains in the case of Fe particles embedded in a MgO single crystal and Fe particles precipitated in a Fe_8Mo_2 amorphous film.iii) We have realized to precipitate partially fine particles in the Fe_8Mo_2 amorphous film by 200 keV electron irradiation with an assist of a heating stage for transmission electron microscopy. A character "N" of granular area wi th the width less than 100 nm was drown in the amorphous film. Some particles in such area was found to have self magnetization by Lorentz microscopy, and small area x-ray analysis confirmed that the atomic concentration of Fe in such particles is la rger than 80% on the matrix.