Magnetic Properties of Extremely Fine Particles of Iron Prepared by Vacuum Evaporation on Running Oil Substrate

Extremely fine particles of iron were prepared by vacuum evaporation onto a running oil substrate. Particles thus prepared were suspended in the oil and their average diameter was about 25 A. From the electron diffraction analysis, it is found that the main constituent of the suspended particles is Fe3O4. Magnetic measurements revealed that these particles showed superparamagnetism whose blocking temperature was distributed between 10 and 30 K, and that the magnetic interaction among these particles was negligibly small.