Effects of NiO addition on the structural, microstructural and electromagnetic properties of manganese–zinc ferrite

Structural, microstructural and electromagnetic properties of NiO doped manganese–zinc (MnZn) ferrites prepared by a solid-state reaction method have been investigated. The continuous doping of NiO resulted in an increase in lattice constant (a), porosity (P) and electrical resistivity (ρ), a decrease in average grain size (D) and bulk density (db), while no obvious change in X-ray density (dX). Hysteresis loss (Ph) increased monotonically with increasing NiO, and its variation could be explained by the relation: Ph∝1/μi3, where μi was initial permeability. Eddy current loss (Pe) first reduced before achieving its minimum, and then rose gradually. The variation of Pe was inconsistent with the classical expression, Pe,cl ∝ D2/ρ, where D and ρ were average grain size and resistivity, respectively, and the excess loss (Pe,exc) could contribute to the Pe. Residual loss (Pr) reduced slowly due to D’s decrease and fr’s increase which were caused by the increase in NiO, where fr was resonance frequency. Finally, the sample doped with 0.10 wt% NiO showed the lowest losses of 207 kW m−3 at 100 °C, 1 MHz and 30 mT.