Abstract: Co-doped manganese-zinc(Mn-Zn) ferrites were prepared by a sol-gel auto-combustion method.Effect of a small amount of cobalt substitution on the structure and magnetic properties of the Mn-Zn ferrites was investigated.As-synthesized Mn_0.4 Zn_0.6-x Co_x Fe₂ O₄ ferrites,characterized by X-ray diffraction(XRD),have demonstrated the pure phase of spinel structure.The saturation magnetization and lattice parameter increase with increasing Co content.It is interesting to note the μ_i-T curve exhibits two maximum peaks and the secondary maximum peak of initial permeability shift to a lower temperature with the increasing of Co content.The temperature of secondary maximum peak could be adjusted by the Co content.The corresponding mechanism was clarified based on the magnetocrystalline anisotropy compensation model.