THE FORMATION AND THE MAGNETIC PROPERTY OF Fe, Co AND Ni FINE METAL PARTICLES
铁、钴、镍金属超微粒的制备与磁性

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.