The initial permeability μ' (at 0.1 GHz) of Ba3Co2R0.1Fe23.9O41 (x=0.1, R= Gd, Dy, Ho, Yb) samples is higher than that of the Co2Z ferrite without substitution. In particular, μ' of Gd3+ substituted Z-type ferrite sample (x=0.1) is the highest of all samples. The substituted sample of Ba3Co2TixZnxFe24-2xO41 with x= 0.85 has a maximumμ' of 24, which is twice as large as that of the non-substituted sample with x=0. Ba3Co2-2x LixFe24+xO41(x=0-1.0) are also prepared. The sample with x=0 showsμ'of 8 at 50MHz. The maximumμ' is 24.5 at x=0.3. An apparent magnetic anisotropy constant K*, calculated by using HA* and MS, decreases. Therefore, the decrease of the magnetic anisotropy contributes to the increase of μ'.