Dielectric behaviour of erbium substituted Mn-Zn ferrites

Dielectric properties such as dielectric constant (e′) and dielectric loss tangent (tan□δ) of mixed Mn-Zn-Er ferrites having the compositional formula Mn0.58Zn0.37Fe2.05−xErx04 (where itx = 0.2, 0.4, 0.6, 0.8 and 1.0) were measured at room temperature in the frequency range 1–13 MHz using a HP 4192A impedance analyser. Plots of dielectric constant (e′) vs frequency show a normal dielectric behaviour of spinel ferrites. The frequency dependence of dielectric loss tangent (tan δ) was found to be abnormal, giving a peak at certain frequency for all mixed Mn-Zn-Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. Plots of dielectric constant vs temperature have shown a transition near the Curie temperature for all the samples of Mn-Zn-Er ferrites. However, Mn0.58Zn0.37Er1.0Fe1.05O4 does not show a transition. On the basis of these results an explanation for the dielectric mechanism in Mn-Zn-Er ferrites is suggested.