Effect of Surface Layer on the Magnetic Characteristics of Mn-Zn Ferrite

It was found that mechanical polishing of Mn-Zn ferrite cores after annealing to remove the surface oxide layer results in great improvements in magnetic properties. The small-signal and large-signal characteristics of ring-shaped cores were measured, and then about 50 μm of surface material on the upper and lower surfaces, as well as on the inner and outer circumferences, was removed by polishing. The μ_s was found to be increased by about 30 percent, and the tanδ value was also slightly higher. It was inferred that removal of oxidized (nonmagnetic) material enabled freer domain wall motion, for lower hysteresis losses.