The spinel ferrite of compositions Ni0.2Mg0.8−x ZnxFe2O4 (x = 0.2, 0.4, 0.6, 0.8) are synthesized using microwave double sintering technique. X-ray diffraction study reveals formation of single phase spinel cubic structure. The lattice parameter (a), average crystallite size (D) and bulk density (ρb) are increasing with zinc content. Fourier-transform infrared spectra are recorded to locate octahedral and tetrahedral sites. The dielectric constant (εr), loss tangent (tanδ), ac, dc-electrical conductivities (σac and σdc) are increasing while Curie transition temperature (Tc) and activation energies (Ea) are decreasing with zinc substitution. Power law fit is applied to logσ versus logω plots to evaluate dc-electrical conductivity and exponent (n) at room temperature. Electrical conduction mechanism and relaxation time (τ) are reported from impedance analysis. Hysteresis loop attributes that saturation magnetization (Ms), anisotropy constant (K1) and coercivity (Hc) are decreasing with substituent. Low coercivity of 1.96–2.89 G obtained is suitable for magnetic recording applications. © 2016 Elsevier B.V.