Effects of grain size on the residual loss of Mn–Zn ferrites

The effect of grain sizes on the electromagnetic properties of Mn–Zn ferrites has been studied up to MHz range. The average grain sizes ranging between 2 and 5 μm were obtained by varying the sintering time from 2 to 12 h. The total power loss at 1 MHz, 25 mT, and 100 °C increased with grain size. The hysteresis loss decreased with increasing grain size, while the eddy current loss and the residual loss increased. The residual loss showed a drastic increase at the grain size around 4 μm, which confirms that the residual loss due to the domain wall resonance should be taken into account at a grain size greater than the monodomain dimension.