Comparison of DC-bias superposition characteristics of low-temperature-fired NiCuZn and MgCuZn ferrites with low Bi₂O₃ doping mode

Low-temperature-fired MgCuZn (Mg_0.3+XCu_0.2Zn_0.5−XFe_1.98O₄: X = 0, 0.02, 0.04, 0.06, 0.08, 0.1) and NiCuZn (Ni_0.3+YCu_0.2Zn_0.5−YFe_1.98O₄: Y = 0, 0.02, 0.04, 0.06, 0.08, 0.1) ferrites under low Bi₂O₃ doping mode were prepared by the conventional solid-state reaction method. Their magnetic properties, especially DC-bias superposition characteristics, were compared. With 0.3 wt% Bi₂O₃ as sintering aid, the NiCuZn ferrites could obtain higher permeabilities compared with the MgCuZn ferrites under the same Zn content. However, when the same permeabilities were obtained, the MgCuZn ferrites presented better DC-bias superposition characteristics than the NiCuZn ferrites. The increase in H_c (coercivity) was beneficial to promote DC-bias superposition characteristics. For the same reason, the incremental permeability of the MgCuZn ferrites decreased slowly than that of the NiCuZn ferrites when the permeabilities decreased below 30%. However, when the applied DC-bias superposition became larger, the incremental permeability of NiCuZn decreased slower than that of MgCuZn, which was mainly attributed to the former’s higher B_s (saturation flux density) compared with the latter. Possible mechanisms contributing to the above results were discussed.