Theoretical investigation of some experimental data of Al-substituted MnZn spinel ferrites

The second approach was by trying to find a realistic theoretical model in the literature, then to study the fitting of its equations with the investigated experimental data. We have found that Dyre's macroscopic model is based upon some reasonable assumptions and has approximated end equation for electrical conductivity that fit satisfactorily with the studied experimental data. We have to mention here that its approximated end equation based upon the effective medium approximation (EMA) has fitted well the conductivity data at frequencies greater than a characteristic frequency fc-the onset of AC conduction-while its approximated end equation based upon the percolation path approximation (PPA) has fitted well the conductivity data at frequencies less than the characteristic frequency fc.