Fundamental Study on magnetic-granular films with fine structures

本研究的主题是制作磁性颗粒薄膜的精细结构。磁性颗粒膜是一种新型的磁性物质。具体地，其目的是在非晶薄膜中产生小于几十纳米的精细磁性颗粒区域。迄今为止，还没有一种方法可以研究如此小范围内的磁状态。因此，首先，我们必须实现对小于10 nm的微小颗粒的磁性的观察。为了制作颗粒状区域的图案，要求原始基体为非晶或直径小于1nm的超细颗粒的多晶。i）找到了用直流磁控溅射法制备Fe_8Mo_2非晶薄膜的条件。通过使用配备有场发射电子枪和磁屏蔽电子透镜的透射电子显微镜仪器的洛伦兹电子显微镜，在Fe颗粒嵌入MgO单晶和Fe颗粒沉淀在Fe_8Mo_2非晶薄膜中的情况下，我们成功地观察到了小于10 nm的具有单磁畴的细颗粒的磁性状态。利用透射电子显微镜的加热台，实现了200keV电子辐照Fe_8Mo_2非晶薄膜中部分细小颗粒的析出。在非晶薄膜中发现了一个宽度小于100 nm的颗粒状区域的“N”字。用Lorentz显微镜观察发现，该区域内的部分颗粒具有自磁化，小面积X射线分析证实，该区域内的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.