Effects of Porosity and Grain Size on the Magnetic Properties of NiZn Ferrite

The effects of porosity and grain size on the magnetic properties of NiZn ferrites were examined on groups of specimens with controlled porosity and grain size; both the permeability and the B-H loop were measured. The demagnetizing factor, which is proportional to porosity, was estimated on the basis of the permeability-porosity relation determined. The discussion of the permeability-grain size relation takes into consideration the dependence of domain wall spacing on grain size. The experimental results for the B-H loops indicate that the remanent magnetic flux density is independent of grain size and the coercive field is independent of porosity. Both the remanent magnetic flux density-porosity and the coercive field-grain size relations are explained via the formulas proposed.