Quantitative analysis of the factors increasing coercive force of iron powder cores-influence of porosity

The effect of porosity on coercive force was analyzed quantitatively about iron powder cores with different porosities. The coercive force of the iron powder cores decreased 11.0 A m-1 with a decrease in porosity by 0.01. From the in-situ observation of Kerr effect microscopy, the nucleation of the reverse domain was observed at the local areas along narrow gaps such as a contact interface between particles / the fine pores among the particles, and there are no nucleation of the reverse domain at the coarse pores. It indicates that the local decrease in the diamagnetic field with a decrease in porosity might be reduced in these areas resulting in the coercive force decreases. From this result, densification of iron powder cores can be an effective measure to reduce coercive force.