Core losses and magnetic properties of Mn-Zn ferrites with fine grain sizes

Mn-Zn ferrite with fine grains was obtained by sintering hydrothermal-precipitated ferrite powders. The average grain sizes of the hot isostatically pressed specimens were 1.0-6.8 μm and the relative densities were above 99.3%. The frequency at which the maximum value of μ″ was obtained for the ferrites tends to increase with decreasing grain size, and the core loss at 5 MT and 1-2 MHz attained a minimum value for the ferrite with grain size of 2-3 μm. At 80°C, which is practically the usual operating temperature, the core loss of this specimen is also considerably smaller than those of the commercial ferrites with grain sizes of 7.7-10.9 μm at 0.5-1 MHz. Therefore, the fine-grain ferrite is expected to be useful as a material for high-frequency transformers.