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Surface chemical control and characterization of magnetism of nano-scale thin films, wires and clusters

纳米级薄膜、线材和团簇的表面化学控制和磁性表征

基本信息

批准号：
15087211
负责人：
YOKOYAMA Toshihiko
金额：
$ 34.82万
依托单位：
Institute for Molecular Science (2004-2006)Okazaki National Research Institutes (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

The main subject of the present research is to control the magnetism of magnetic thin films, nanowires and nanoclusters by means of surface chemical techniques such as adsorption of atoms and molecules and surface reactions. Especially, adsorption induced spin reorientation transitions have been investigated from the microscopic point of view. Throughout this project, we discovered a novel important phenomenon, which provides a new characterization technique for nanoscale magnetism. We have found surprising enhancement of the ultraviolet magnetic circular dichroism (MCD) of the photoemission near the work function threshold. The photoemission MCD allows us to observe nanoscale magnetism using photoelectron emission microscopy (PEEM), whose typical special resolution is 10〜40 nm. Usually, MCD PEEM measurements have been performed using third-generation synchrotron radiation soft x rays as a light source, limiting the availability of this method. Moreover, time-resolving power using sync … More hrotron radiation cannot reach subpicosecond (-70 ps in ESRF), which is easily overcome by using ultraviolet lasers. The fact that the enhancement of the UV photoemission MCD was not discovered may be attributed to the poor preconcept that the UV MCD is weak due to small spin-orbit coupling in the valence shell and to the experimental finding that the UV MCD is actually weak when the photon energy is not tuned correctly. In the present study, we found noticeable enhancements of the UV photoemission MCD from Fe, Co and Ni films, which were justified by means of simple band-structure calculations including spin-orbit couplings. The enhancements are as much as two orders of magnitude compared to the usual condition (no photon energy tuning), and the MCD contrast in Ni films amounts as much as 10%. We have constructed UV MCD PEEM systems and have successfully observed beautiful magnetic domain images in. Cs-coated Ni films on Cu(001). We are now preparing a femtosecond time-resolving setup. Less

目前研究的主要课题是通过原子和分子的吸附以及表面反应等表面化学技术来控制磁性薄膜、纳米线和纳米团簇的磁性。特别地，吸附诱导的自旋重取向转变已经从微观的角度进行了研究。在整个项目中，我们发现了一个新的重要现象，这为纳米磁性提供了一种新的表征技术。我们已经发现了令人惊讶的增强的紫外磁圆二色性（MCD）的光电子附近的功函数阈值。光电子发射MCD允许我们使用光电子发射显微镜（PEEM）观察纳米尺度的磁性，其典型的特殊分辨率为10 ~ 40 nm。通常，MCD PEEM测量已经使用第三代同步辐射软X射线作为光源进行，限制了这种方法的可用性。此外，使用同步的时间分辨能力 ...更多信息 hrotron辐射不能达到亚皮秒（ESRF中约70 ps），这通过使用紫外激光器容易克服。没有发现紫外光致发射MCD的增强的事实可能是由于差的先入之见，即紫外MCD是弱的，由于小的自旋-轨道耦合的价层和实验发现，紫外MCD实际上是弱的光子能量时，没有被正确地调谐。在本研究中，我们发现显着增强的紫外光发射MCD从Fe，Co和Ni薄膜，这是合理的通过简单的带结构计算，包括自旋轨道耦合。的增强是多达两个数量级相比，通常的条件下（没有光子能量调谐），和MCD的对比度在Ni膜的金额多达10%。我们已经建立了紫外MCD PEEM系统，并成功地观察到美丽的磁畴图像。在Cu（001）上镀Cs的Ni膜。我们现在正在准备一个飞秒时间分辨装置。少