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Study of X-ray magnetic circular dichroism in magnetic chemistry and surface chemistry

X射线磁圆二色性在磁化学和表面化学中的研究

基本信息

批准号：
10304059
负责人：
OHTA Toshiaki
金额：
$ 21.38万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10304059/
关键词：
XMCD XAFS Surface magnetism Magnetic thin film molecular adsorbate 磁気円偏光二色性(XMCD)磁気異方性

项目摘要

The purpose of this research proposal is to investigate the magnetic interaction between magnetic thin films and adsorbed molecules by use of the X-ray Magnetic Circular Dichroism (XMCD) method. In this year, we have constructed a new soft x-ray beamline in the Photon Factory, whose performance is much higher than that we used before. Thus, it turned out that even very weak XMCD signal can be detected with the new beamline. We have carried out following three subjects.(1) Co L-MCD and O K-MCD study of O and CO adsorbed Co thin films. The magnetism induced by O adsorbate is ferromagnetic, but that induced by CO is antiferromagnetic to the substrate Co magnetism. This result suggests that the adsorption site sensitively affect the magnetic behavior.(2) Ni L-MCD and O K-MCD of CO adsorbed Ni thin films. It is known that the magnetic easy axis is in plane in the Ni thickness of less than 10 ML, and perpendicular in the range of 10-50 ML, and again in plane above 50 ML.It was revealed that CO adsorption extends the region of perpendicular magnetic anisotropy (PMA) to 6 ML-50ML.Furthermore, the induced magnetic moment of CO is ferromagnetic at PMA, and antiferromagnetic at the in plane anisotropy. We succeeded in interpreting these phenomena by a simple chemical bonding scheme.(3) Mn L-MCD of Mn layer and oxidized Mn layer on Co films. Clean Mn has a ferromagnetic coupling with Co, but the exposure of O_2 only affects Mn and MnO is formed, which has, in turn, antiferromagnetic coupling with Co.These magnetic behaviors depend on many parameters such as the kind of adsorbed molecules, adsorption site, thickness of magnetic films. Systematic study is necessary to get a deeper insight in chemical bonding of molecules and metals.

本研究的目的是利用x射线磁圆二色性（XMCD）方法研究磁性薄膜与吸附分子之间的磁相互作用。这一年，我们在Photon Factory中构建了一条新的软x射线光束线，其性能比我们以前使用的要高得多。因此，事实证明，即使是非常微弱的XMCD信号也可以用新的波束线检测到。我们进行了以下三个课题。(1) Co和Co吸附Co薄膜的Co - L-MCD和O - K-MCD研究。O吸附物诱导的磁性是铁磁性的，而CO诱导的磁性是反铁磁性的。这一结果表明，吸附位置对磁性行为有敏感的影响。(2) CO吸附Ni薄膜的Ni L-MCD和O K-MCD。在Ni厚度小于10 ML范围内，磁易轴呈平面分布；在10 ~ 50ML范围内，磁易轴呈垂直分布；在50ML以上范围内，磁易轴又呈垂直分布。此外，CO的感应磁矩在PMA处为铁磁性，在平面各向异性处为反铁磁性。我们用一个简单的化学键图式成功地解释了这些现象。(3) Co膜上Mn层和氧化Mn层的Mn - L-MCD。干净的Mn与Co发生铁磁偶联，而O_2的暴露只影响Mn，形成MnO， MnO与Co发生反铁磁偶联。这些磁性行为与吸附分子的种类、吸附位置、磁膜厚度等参数有关。为了更深入地了解分子和金属的化学键，系统的研究是必要的。