Magnetic and dielectric behavior of terbium substituted Mg1−xTbxFe2O4 ferrites

The effects of concentration of terbium (Tb) on ferromagnetic resonance (FMR), relative initial permeability, morphology, and dielectric properties of MgFe2O4 ferrites were studied. It is found that FMR line-width and FMR position of magnesium–terbium (Mg–Tb) ferrites are found to fluctuate with the increase of Tb-content. The increase in FMR line-width is attributed to the charge transfer mechanism and inhomogeneity in the samples (TbFeO3). The relative initial permeability decreases gradually as a function of Tb-content. The magnetic loss factors of substituted samples exhibit decreasing behavior in the frequency range 1 kHz to 10 MHz. Terbium substituted samples have lower dielectric constant as compared to the pure MgFe2O4 ferrite. The decrease in dielectric constant is attributed to the retardation in electron exchange mechanism caused by lockup among iron and terbium ions. An irregular behavior of the dielectric loss is found, which is related to the hopping probability of charges in these ferrites. A decrease in the ac conductivity is observed beyond 8 MHz and this corresponds to the occurrence of dielectric loss. The low magnetic and dielectric behavior makes these ferrite materials suitable for their applications in microwave devices.

Eleven samples of the nominal compositions Mg1−xTbxFe2O4 were prepared by ceramic method. The influence of terbium substitution on the FMR, relative initial permeability, loss factor, and dielectric properties has been studied in details. The sample Mg0.98Tb0.02Fe2O4 exhibits minimum FMR line-width (ΔHFWHM = 746 Oe). The incorporation of terbium elucidates small values of relative initial permeability and loss factor. A significant reduction in the values of dielectric constant has been observed with the increase of terbium ions. These properties make these materials suitable for microwave devices applications.Figure optionsDownload as PowerPoint slideHighlights
► The synthesized samples Mg1−xTbxFe2O4 exhibit minimum FMR line-width (i.e. 746 Oe) as compared to reported line-width of spinel ferrites.
► The substituted samples exhibit smaller values of the magnetic loss factors.
► The dielectric constant is decreased by the terbium incorporation.
► The substituted samples revealed small values of dielectric loss.
► Low magnetic and dielectric properties make ferrites suitable materials for microwave devices applications.