Effects of Co-substitution on DC-bias-superposition characteristic of the NiCuZn ferrites

Low-temperature-fired Ni0.5−xCu0.2Zn0.3CoxFe1.95O4 (0.00≤x≤0.10, with 0.02 intervals) ferrites were produced by the conventional ceramic technique. Both microstructure and sintering density changed little in samples sintered at 900 °C. Saturation magnetic flux density gradually increased with increase in Co-substitution content. Coercive force first decreased with x value and obtained the minimum with x=0.04, then it continuously increased with x value. Permeability presented a fully opposite variation trend compared with coercive force. Furthermore, coercive force had a more important influence on DC-bias-superposition characteristic than that of saturation magnetic flux density. The sample with 0.04 Co-substitution favored to obtain a higher incremental permeability (permeability with magnetic field superposition) under a relatively low superposition magnetic field. And the sample with 0.08 Co-substitution favored to obtain a steady incremental permeability under different superposition magnetic fields.