Metallic magnetic fluids containing Fe, Co or FeCo alloy ultrafine particles were prepared by vacuum evaporation method, and then the magnetic properties and particle sizes of magnetic fluids were studied. Magnetic fluids with alloyed Fe-Co particles were obtained by evaporating the mixed Fe and Co raw powders in vacuum onto the oil with surfactant. The particle sizes were in the range of 30Å to 35Å. In order to control the particle size Ar gas was introduced into the chamber and magnetic fluids were prepared at various pressures. The particle sizes in the fluids were increased from 30Å to 80Å with Ar pressure.
We also attempted to obtain a metallic magnetic fluid by arc-plasma method in Ar-H₂ atmosphere. The ultrafine particles were collected into the oil successfully with venturi scrubber, but further research is needed to generate smaller particles in order to obtain stable colloids.