Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Preparation and Coercivity of Cobalt Ultrafine Particles by Reduction of Multilayered CoO–SiO Films
Yoshichika BandoTakahito Terashima
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1986 Volume 59 Issue 2 Pages 607-612


Films containing Co ultrafine particles were prepared by hydrogen reduction of periodically multilayered CoO–SiO films which were formed by alternating deposition of CoO and SiO. The films containing Co particles maintained the periodicity similar to the original films. Using samples of CoO single layer sandwiched between SiO layers, highly dispersed Co particles in the reduced sample were observed by transmission electron microscopy. The average size of the Co particles was almost as large as the thickness of CoO layer. The coercivities of the multilayered films containing Co particles were measured at room temperature and 77 K; they decreased with decreasing particle size from 20 nm to 3nm. Superparamagnetism was observed for the Co particles with average sizes below 4nm at room temperature. The formation and the magnetic property of the Co ultrafine particles in the Co–SiO system is dicussed.

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