The dependence of the coercivity on the volume packing fraction for magnetic particles

The advanced method of the dilution of magnetic particles with α-FeOOH particles was studied. This method permits the determination of the dependence of coercivity on the packing fraction and the evaluation of Hc(0) has become possible. The coercivity of Co-adsorbed γ-Fe2O3or CrO2particles decreases rather slowly with the packing fraction compared with γ-Fe2O3or Co-doped γ-Fe2O3particles. This behavior is interpreted by the existence of some nonmagnetic surface layers on the particles. These layers are thought to make the magnetic particle interactions weak to prevent the apparent coercivity from decreasing steeply.