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Improvement of the magnetic properties of new compound SmFe_7 by nitrogenation

氮化提高新型化合物SmFe_7磁性能

基本信息

批准号：
12650321
负责人：
NAGATA Yujiro
金额：
$ 2.3万
依托单位：
AOYAMA GAKUIN UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650321/
关键词：
hard magnetic material SmFe_7 single crystal magnetic anisotropy Sm_6Fe_<23>

项目摘要

SmFe_7 is known to have large spontaneous magnetic moment and magnetocrystalline anisotropy, which are equivalent to those of NdFeB hard magnetic material. However, although single crystal of SmFe_7 was obtained by a flux method, polycrystalline specimen has not been obtained. This seems to be due to that SmFe_7 phase exists in a narrow composition and temperature region. This study was performed to identify SmFe_7 phase in the phase diagram of Sm-Fe system, to improve magnetic properties by nitrogenation or substitution, and to search new materials in Sm-Fe system. SmFe_7 phase was identified by x-ray diffraction studies for arc-melted specimens that were annealed at 900℃〜1200℃ and quenched into water. It was revealed that SmFe_7 phase appears at temperatures between 1030℃〜950℃. However, it was unsuccessful to obtain single SmFe_7 phase.Nitrogenation of SmFe_7 crystal was unsuccessful. This is due to the oxidation of Sm. It is well known that Sm is the most oxidizable metal in the rar … More e-earth metal. When SmFe_7 crystal was heated in the stream of nitrogen gas, it was oxidized easily by the residual oxygen even at lower temperatures below 400℃ and decomposed. To overcome this difficulty new annealing system, which can be evacuated to a vacuum level more than 10^<-7> Torr, is necessary. However, we could not equip these type of system at present study. Therefore, we studied the effect of substitution of non-magnetic Al to the crystallographic and magnetic properties of SmFe_7 by comparing with the effect to other compounds in the Sm-Fe system. It was for the first time to study Al substitution effect systematically by using single crystal specimens of various phases in Sm-Fe system. Although Al substitution decreases saturation moment of Sm-Fe compounds, it is effective to increase Curie temperature and magnetocrystalline anisotropy. Moreover, in the process of crystal growth of SmFe_3, new compound with a formula of Sm_6Fe_<23> was discovered in this study. Sm_6Fe_<23> contains a lot of Fe atoms in unit cell, and, therefore, it is very interesting as a practical magnetic material. Less

SmFe_7具有较大的自发磁矩和磁晶各向异性，与NdFeB硬磁材料相当。然而，虽然通过助熔剂法获得了SmFe_7单晶，但尚未获得多晶样品。这似乎是由于SmFe_7相存在于较窄的成分和温度范围内。本研究旨在识别Sm-Fe系相图中的SmFe_7相，通过氮化或取代来改善磁性能，并寻找Sm-Fe系新材料。通过X射线衍射研究，对900℃〜1200℃退火并在水中淬火的电弧熔炼样品进行了SmFe_7相的鉴定。结果表明，SmFe_7相在1030℃〜950℃之间出现。但未能成功获得单一SmFe_7相。SmFe_7晶体的氮化未成功。这是由于Sm的氧化造成的。众所周知，Sm是稀土金属中最易氧化的金属。 SmFe_7晶体在氮气流中加热时,即使在400℃以下的较低温度下也很容易被残余氧氧化而分解。为了克服这个困难，需要新的退火系统，该系统可以抽真空至超过10^<-7>托的真空度。然而，我们目前的研究还无法配备此类系统。因此，我们通过与Sm-Fe系中其他化合物的比较，研究了非磁性Al的替代对SmFe_7晶体和磁性能的影响。首次利用Sm-Fe系各相单晶样品系统研究Al替代效应。尽管Al取代降低了Sm-Fe化合物的饱和矩，但它对于提高居里温度和磁晶各向异性是有效的。此外，在SmFe_3晶体生长过程中，本研究还发现了分子式为Sm_6Fe_<23>的新化合物。 Sm_6Fe_<23>晶胞中含有大量Fe原子，因此作为实用的磁性材料非常有趣。较少的