Ferrite samples of the general formula Mg1+x Ti (x) Er (y) Fe2-2x-y O-4; 0.1 <= x <= 0.9, y = 0.025 were prepared using the standard ceramic method. The final sintering temperature was 1,200 degrees C with heating rate 4 degrees C/min during 100 h. X-ray diffraction analysis was carried out to assure the formation of the spinel structure. The effect of Ti4+ ion concentration on the structural and the electrical properties of the investigated samples is studied. It change the iron ion concentration from 2 to 2-2x thereby decreasing the number of ferrous ions on octahedral sites, with a consequent decrease the dielectric constant. The most important result of gamma-irradiation on the electrical properties is the change of ratio Fe2+/Fe3+ on the octahedral site leading to increase the conductivity as well as the dielectric constant. The variation of the thermoelectric power with a temperature is performed, the common feature of all compositions is the fluctuation of Seebeck coefficient between positive and negative over the whole range of temperature. This indicates that the charge carriers are electrons and holes, depending on both the temperature range and the additive in the ferrite samples.