MORPHOLOGY AND POROUS TEXTURE OF IRON FINE PARTICLES WITH RELATION TO THEIR MAGNETIC-PROPERTIES

The effects of a silica film as thin as 0. 4 nm on the variation of morphology of particles were investigated by gas adsorption, electron microscopy, X-ray diffraction and magnetic measurements. By introducing heat treatment of the silica-coated haematite particles at 700 degree C in air prior to reduction, acicular iron particles having the crystallites grown along the elongated direction of the particles were obtained. An increase in coercivity from 1075 to 1530 Oe is attributed to the increase in shape anisotropy.