Some ac electrical properties of Li–Mg ferrites

The ac resistivity (ρac), dielectric constant (ϵ′), dielectric loss tangent (tan δ) and initial permeability (μi) of mixed Li0.5−x/2MgxFe2.5−x/2O4 (where x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) ferrite system were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The resistivity of all the samples decreased with increase in frequency, indicating that the samples exhibited normal ferrimagnetic behavior. The compositional variation of resistivity and dielectric constant indicated the inverse trends of each other. The sample with x = 0.3 showed the lowest resistivity and the highest dielectric constant. The dielectric loss tangent showed maxima at 3 kHz for x = 0.2 samples and at 15–20 kHz for x = 0.3 and 0.4 samples. All of the variations are explained on the basis of Fe2+/Fe3+ ion concentration on octahedral sites as well as the electronic hopping frequency between Fe2+ ⇔ Fe3+ ions.