Magnetic Properties of Ferromagnetic Metal Alloy Fine Particles Prepared by Evaporation in Inert Gases

Abstract

Single domain fine particles about 150 Å in diameter, of alloys of Fe, Co and Ni were prepared by evaporation in an atmosphere of argon at 3 Torr. The particles were coupled with each other like a necklace. The X-ray diffraction analysis revealed that the lattice parameters of the alloy particles agreed with those of the original bulk alloys within an experimental error of 0.3%. It was indicated, however, that they might be smaller than the latter within that error. The maximum coercive force observed in Fe–Co alloys was about 1.5 kOe. It was found that the oxidation of Fe–Co alloys can be prevented by adding some Ni. The magnetic orientation of particles caused by application of a magnetic field during the evaporation was studied. In a magnetic field of 0.5 kOe the necklace structure was aligned parallel to the field and a magnetic anisotropy of 3.5×10⁵ erg/g appeared in this oriented sample. This strong anisotropy is considered to be due to a shape anisotropy induced by alignment.