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铁、钴、镍金属超微粒的制备与磁性

李华 龚伟

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铁、钴、镍金属超微粒的制备与磁性

李华, 龚伟

THE FORMATION AND THE MAGNETIC PROPERTY OF Fe, Co AND Ni FINE METAL PARTICLES

LI HUA, GONG WEI
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  • 用气体蒸发法制备粒径在100—800?之间的铁、钴、镍金属超微粒。超微粒的生长机制与气压相关,在低气压下(P3Torr)为凝聚生长。电子显微镜观察到铁的非晶态超微粒。X射线衍射表明:铁、镍超微粒的晶格结构与相应的块物质相同,但钴超微粒有所不同,粒度为200—300?的钴为fcc结构。室温下,铁、钴、镍超微粒最高矫顽力分别为1000,1500和450Oe,对应的平均粒度为210,200和320?,其数值与理论计算的单畴颗粒尺寸大致相同。其饱和磁化强度随粒度的减小而单
    Fine particles of Fe, Co and Ni with average diameters from 120? to 800? were prepared by a gas evaporation method in the atmosphere of argon or nitrogen. We revealed that homogeneous nucleation growth was the dominant growth mechenism of the particles prepared at low pressure (<3 Torr). The zigzag chains could be explained by the magnetic connection of particles when each particld had a multi- domain structure, and the straight chains when each particle had a single domain. The X-ray diffraction revealed that the crystal structure of Fe and Ni fine particles was the same as the bulk materials and the crystal strcuture of Co fine particles with average diameter from 200? to 300? was f.c.c. which differed from h.c.p.of bulk cobalt at room temperature. When the diameter of the particles was about 210?, 200? and 320?, which is nearly the single domain size of Fe. Co and Ni particles, the maximum corecivity of Fe, Co, Ni fine particles was 1000 Oe, 1500 Oe and 450 Oe at room temperature respectively. The saturation magnetization decreased with the decrease ef panicle size due to the increase of the volume percent of the oxide layers and the numbers of the superparamag-netic particles. A noneollinear configuration of the magnetic moments existed in oxide surface layers for fine particles.
    • 基金项目: 中国科学院物理研究所磁学开放研究实验室资助的课题
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  • 文章访问数:  7043
  • PDF下载量:  620
  • 被引次数: 0
出版历程
  • 收稿日期:  1990-09-20
  • 刊出日期:  1991-04-05

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