Magnetic properties of fine iron particles

Iron particles were prepared by a gas evaporation method in a nitrogen atmosphere. The particle size, shape, and magnetic properties were influenced by the nitrogen pressure. Particles prepared by this method were relatively stable in air and were not seriously oxidized. The recoilless fraction is low for the oxide layer, so that it cannot be detected at room temperature by Mossbauer spectrum. A superparamagnetic peak associated with the oxide microcrystal layer did not occur in the Mossbauer spectra due to the action of the magnetic field from the iron core and the interaction between iron particles and the low Debye temperature. From the electron micrography, the magnetic reversal process seems to be determined by a chain‐of‐spheres mechanism but Hc∼T curve cannot coincide with the Ms∼T curve at low temperatures. An increase of Hc may be associated with magnetic anisotropy. It is found that the magnetization versus temperature shows an anomalous increase in M(T) at higher T. We think that this means tha...