Intrinsic Coercivity of BaFe12−xCrxO19

The influence of the partial substitution of Cr for Fe in BaFe12O19 on the intrinsic coercive force has been investigated. The specimens BaFe12−xCrxO19 (x = 0 to 3.0) were prepared by the ordinary powder method. The intrinsic coercive force iHc, saturation magnetization Is, and anisotropy constant K, at room temperature and Curie temperature Tc were measured. A large increase in coercive force under the effect of Cr (iHc = 8000 Oe at x = 3.0) was observed. The critical radius Rc for single-domain particles was determined for each composition. It becomes larger when the Cr concentration is increased. For instance, the value of Rc at x = 3.0 is three times larger than the value of Rc at x = 0. The increase in anisotropy field could not be expected. It is concluded that the rapid rise of coercive force with Cr concentrations is due to the onset of single-domain behaviour at higher concentrations.