Fine iron particles having super high coercivity

Fine iron particles having coercivity higher than 2000 Oe were produced by the conventional method which is conmercially used,i.e, the reduction of acicular goethite particles with hydrogen gas. This could be done by adsorption of Nd
³⁺
or Ce
³⁺
ions together with B
³⁺
ions on the surface of the goethite particles. Electron micrographs show that the particles have very smooth surface and few micropores, and are isolated from each other. The optimum size of the iron particles is around 0.13 μm in length and 0.02 μm in width. The specific surface area of this powder is about 38 m
²
/g, which is much lower than the ordinary ones. This super high coercivity may be due to the peculiar microstructure of the amorphous iron oxide layer which is coupled with the iron core, together with the well defined single domain behavior of the iron particles.