Soft magnetic composite materials find increasing use in electrical motors, replacing existing laminate materials. In this study, the composites have been fabricated with micro- and nano-sized highly pure iron powders coated by polyester and phenolic resins. Soft magnetic composite materials have been pressed into ring type for magnetic properties measurement, and bar type for mechanical properties measurement over the pressure range up to 870 MPa. Some
samples have subsequently been heat treated to 300°C. The effect of the amount of organic materials on the magnetic properties like as permeability, magnetic flux density, core loss and green density were investigated. And electrical resistivities were also examined. On the addition of the organic coating materials of 5 wt%, green density of the compacted composites is most high of 6.9 g/cm3, and magnetic properties are also better. For the case of 5 wt% polyester resin, the effect of powder size with 100 nm, 3 μm, 10 μm and 53 μm were examined. Both the green density and the magnetic properties are best for the particle size of 10 μm. Fine particles below 3 μm easily agglomerate each other, and
homogeneous coating of each particle surface is difficult.