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. (c) 2012 Elsevier B.V. All rights reserved.