Effect of Tb3+ substitution on structural, electrical and magnetic properties of sol-gel synthesized nanocrystalline nickel ferrite

A series of NiTbxFe2−xO4 (x = 0.0, 0.1, 0.2, 0.3) nanoparticles with small size have been prepared using sol-gel technique. The effect of Tb3+ substitution on the crystalline phase, crystallite size and magnetic, electrical and dielectric properties has been investigated in detail. The lattice constant shows an increasing trend with increase in Tb3+ ion concentration. The high frequency tetrahedral vibration band ν1 and the low frequency octahedral vibration band ν2 in the FTIR spectra are in the reported range. The observed shift in ν2 towards lower wave number side with increase in terbium concentration suggests the occupation of Tb3+ ions predominantly on octahedral sites. Saturation magnetization is found to decrease with terbium addition. Magnetic hysteresis loss is observed to decrease up to x = 0.2 and then increases. The room temperature resistivity values are found to increase with terbium content. The observed dielectric dispersion with frequency is explained on the basis of Maxwell-Wagner two-layer model and electron hopping mechanism which is responsible for conduction and polarization. Dielectric constant and dielectric loss are found to decrease by terbium addition and is explained in terms of the decrease in hopping rate due to the substitution of Fe3+ ions by Tb3+ ions on the octahedral sites. The increased resistivity and reduced dielectric loss attained in terbium doped ferrite is promising as it is desirable for high frequency applications.