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High-Quality-Magnetic Materials Fabricated by Cluster-Assembling

通过团簇组装制备高质量磁性材料

基本信息

批准号：
08505004
负责人：
SUMIYAMA Kenji
金额：
$ 36.03万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

We would like to establish the new paradigm, functional-material-fabrication from nano-scale clusters, which correspond to units of functional elements. The summaries of our resarch activities for three years are as follows.1) We designed and constructed a laser-vaparization type cluster deposition system with a time-of- flight mass spectrometer. The mass-spectrometric studies of transition metal clusters indicate that the clusters consiting of 7,13,15,19 atoms are magic numbers for Fe, Ti, Ta, Nb and Zr, while no marked magic number effect for Ni and Co.2) We analyzed the Fe-oxide cluster formation process by mass-spectrtometry. The abundnances of Fe_<13>O_8, Fe_<43>O_<20> are much stronger the others'. This feature is confirmed by the first principle molecular orbital calculations.3) Superparamagnetic to ferromagnetic transition is detected at around 9 nm for mono-dispersive Co clusters produced by plasma-gas-condensation.4) The assemblies of CoO coated Co clusters show very large tunneling type magnetoresistance. The logarithmic conductivity shows T^<-1> dependence, indicating monodispersivity in the cluster size and uniformity of the CoO layer thickness.5) XAFS, MCD and Magneto-optical Kerr spectra were observed for Co cluster assembled films. Two monolayered CoO is formed at the cluster surface. In the inner metallic Co cores , fcc is predominant for the cluster size, d= 6 nm. With increasing d from 6 to 13 nm, the volume fraction of hcp increases. The magneto-optical Kerr effect is enhanced at the low wave length region.

我们希望建立新的范例，功能材料制造从纳米尺度簇，这对应于功能元素的单元。本文对三年来的研究工作进行了总结，主要内容如下：1）设计并搭建了一套激光蒸发式团簇沉积系统，并配备了飞行时间质谱仪。过渡金属原子团簇的质谱研究表明，Fe、Ti、Ta、Nb和Zr的7、13、15、19原子团簇是幻数效应，而Ni和Co的幻数效应不明显。Fe_O_8<13>、<43>Fe_2O_3<20>的丰度明显高于其它两种。第一性原理分子轨道计算证实了这一特征; 3）等离子体-气体凝聚法制备的单分散Co团簇在9 nm附近发生了超顺磁到铁磁的转变; 4）CoO包覆Co团簇组装体表现出很大的隧穿型磁电阻。对数电导率表现出T^<-1>依赖性，表明团簇尺寸的单分散性和CoO层厚度的均匀性。5）观察到Co团簇组装膜的XAFS、MCD和磁光克尔谱。在团簇表面形成两个单层CoO。在内部的金属Co核，fcc是占主导地位的集群的大小，d= 6 nm。随着d从6增加到13 nm，hcp的体积分数增加。磁光克尔效应在低波长区增强。