Magnetic Properties of Ferromagnetic Metal Fine Particles Prepared by Evaporation in Argon Gas

Abstract

Fine particles of Fe, Co and Ni were prepared by evaporation in the atmosphere of argon gas at low pressure. The diameters of the particles ranged from about 100 Å to 2000 Å. Magnetization of particles was measured by magnetic balance. For Fe and Co the saturation magnetization of the finest and the most coarse particles were about 20 per cent and 90 per cent of those of bulk metals, respectively. For Ni, it was more than 80 per cent and the particle size dependence was less than for Fe and Co. The remanent magnetization and the coercive force were largest for the particle diameter of 300 Å of Fe and Co. The effect of superparamagnetism for smaller particles was not observed. When deposited in magnetic field, long chains of particles appeared along the field direction. Such specimens showed hysteresis curves much more convex than that of randomly oriented ones and remanent magnetization twice as large.