In this paper, we studied the substitution of Fe3+ ions in BaFe12O19 crystal by Co2+-Ti4+ and Cu2+-Nb5+ ions. Two systems of single cry stals of BaFe12-2xCoxTixO19(with x=0, 0.04, 0.09, 0.13, 0.27, 0.68) and BaFe12-x(Nb1/3Cu2/3)xO19(with x = 0, 0.28, 0.44, 0.60) were grown from Bi2O3 melts. Magnetization a and anisotropy constant K1 of the above samples were measured in the temperature range of 100-300K. For the substitution with Co2+-Ti4+ ions, it was found that when x = 0.09 σ and K1 increased slightly with x at the beginning and decreased rapidly when x > 0.09 until K1→ O at x≈ 1.1. In the case of substitutions with Cu2+-Nb5+, the σ value was nearly the same in the studied compositions and showed a slightly increasing trend with increasing x; while K1 decreased monotonously with x. Our results were qualitatively discussed with the model of site occupation of substitution ions in the M-type hexagonal ferrite.
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