Magnesium is replaced systematically by zinc in Ni0.2Mg0.8-xZnxFe2O4 (x = 0.2–0.8) prepared by microwave-assisted solid-state reaction route. The structure is confirmed by X-ray diffractograms. An improvement in initial permeability is observed with substituent in Ni0.2Mg0.8-xZnxFe2O4 due to increase in average grain size. The obtained permeability values are varying between 106 and 687 at 1 MHz. The permeability plots revealed that Curie-transition temperature (Tc) is decreasing with increase in zinc. Both x = 0.2 and 0.4 compositions show low relative loss factor of order 10−5 to 10−4, which are exhibiting required magnetic properties for transformer and inductor core applications. © 2016 The American Ceramic Society