Properties of ferromagnetic micropowders

Abstract

Very small particles of iron, cobalt, and iron-cobalt alloys have been prepared by an evaporation-condensation technique. The crystal structure and shape of these particles have been investigated by X-ray diffraction and electron microscopy. The iron and alloy particles were all found to be bcc and the cobalt particles fcc. No hcp cobalt was observed. The shape of all particles was predominantly spherical. The electron microscope showed that the particles possessed a distribution of sizes and were linked together to form chains. Magnetic measurements have been carried out at 290 K on assemblies of these particles. Coercivity, saturation and remanence curves obtained using a Faraday balance magnetometer and pulsed field magnetometer are presented. These show the particles to have fairly high coercivities (typically 1 kOe) but fairly low remanence to saturation ratios (typically 0.25).