Electromagnetic properties of Mn-doped NiCuZn-ferrites

In this paper, the effect of Mn3+ doping on the high- and low-frequency electromagnetic properties of NiCuZn-ferrites is investigated. There is an optimum Mn3+ concentration at which low-frequency properties such as initial permeability and power losses attain maximum and minimum values, respectively. Simultaneously, the high-frequency losses increase. This optimum Mn3+ concentration is found to depend on iron deficiency of material composition. The low- and high-frequency behaviors of the material are found to be very consistent with the characteristics of the microstructure. An explanation according to which manganese, when added at concentrations where the total trivalent cation amount of the material remains slightly below stoichiometry (i.e. Fe3++Mn3+⩽2), acts as grain growth promoter is proposed. At higher concentrations, the fill of the cation vacancies depresses grain growth and results to fine microstructures, which is negative for the low-frequency but positive for the high-frequency properties.