We fabricated by solid-state ceramic technique single-phase mixed spinel ZnxMg0.3−xCu0.7Al0.3Fe1.7O4 with x index from 0.05 to 0.25, step 0.05 for the first time. The goal was to study the effect of cation doping on internal structure and magnetic properties of the material. The ferrites werefirst characterized by X-ray diffraction to confirm their purity. Magnesium and Zinc cations showed tetrahedral site preference, while Aluminum cations preferred the octahedral site. The effective magnetic moment and exchange interaction increased with the Zinc content. The pure single phase structures allowed us to investigate the vibrational spectra based on the symmetry conditions. We found only two infrared bands, while based on symmetry calculation of the factor group, four bands are predicted. The number of atoms and their relative arrangement in the crystal are the main criteria to define the active vibrational bands as predicted by factor group theory and the magnetic response of the material.