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M-type hexaferrites BaFe 12− x M x O 19 (M = Ga, Al, Cr) were prepared by ball milling and sintering. X-ray diffraction patterns indicated the formation of the hexaferrite phase at a sintering temperature of 1100 °C, with small amounts of α-Fe 2 O 3 secondary phase in the Al and Cr substituted hexaferrites. Scanning electron microscopy indicated that the particle size does not change with Ga substitution, and decreases with increasing Al and Cr substitutions. The atomic ratios determined by energy dispersive X-ray spectroscopy were close to stoichiometric ratios. Mossbauer spectra were used to determine the site preference for each type of cationic substitution. The results of the magnetic measurements indicated constancy of the anisotropy filed and similarity of the behaviors of the first anisotropy constant ( K 1 ) and the saturation magnetization with increasing substitution level for all types of substitutions. The coercivity was found to increase with increasing the concentrations of the substituents, and a maximum increase in the coercivity for the Al substituted hexaferrites was observed. |
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