Effects of Co-substitution on wide temperature ranging characteristic of electromagnetic properties in MnZn ferrites

MnZn ferrites with the chemical formula Mn0.700-xZn0.233CoxFe2.067O4 have been prepared by conventional ceramic technique. Toroidal cores were sintered at 1350 deg. C for 4 h in N2/O2 atmosphere with 4% oxygen. Then the influence of Co-substitution on the temperature dependence of electromagnetic properties in MnZn ferrites were investigated by measuring the magnetic properties and DC resistivity over a wide temperature ranging from 25 to 120 deg. C. The results show that Co-substitution in MnZn ferrites results in the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to lower temperature. The Curie temperature, resonance frequency, DC resistivity and the activation energy of electron hopping increase with the increase of Co-substitution. Moreover, the drift mobility decreases with the increase of Co-substitution. However, there is little influence of Co-substitution on the microstructure with the increase of Co-substitution.