Cu2+ substituted Mg-Co ferrite has improved dc electrical resistivity and magnetic properties

•The samples Cu2+ substituted Mg0.5-xCuxCo0.4Fe2O4 were successfully prepared by a solid-state reaction method.•Larger ionic radii of Cu2+ than that of Mg2+ decreases the lattice constant.•SEM micrographs exhibit uniform size cubic crystals with average grain size values between 1 and 1.5 µm.•Two absorption bands given by FTIR within the range of spinel structure confirm their nature.•The activation energy and the DC electrical resistivity decrease with Cu2+ substitution while the samples' magnetic saturation and coercivity decrease with Cu2+ concentration.