Abstract
In this work, we studied the substitution effect of iron by gallium on the structural, magnetic and electrical properties of the ferrite system; Ni0.5Cu0.25Zn0.25Fe2-xGaxO4 (x = 0-1.0), synthesized by using the urea combustion method. XRD patterns of the samples calcined at 700 C show only cubic spinel ferrite with an average crystallite sizes in the range of 40-54 nm. The lattice parameters were slightly changed with increasing Ga content which can be explained on the basis of the relative ionic radii of Ga3+ and Fe3+ ions. FT-IR measurements show two fundamental absorption bands, assigned to the vibration of tetrahedral and octahedral complexes, which were slightly changed with increasing Ga content. Mossbauer measurements enable us to predict the possible cation distribution of the system. It was found that Ga3+ ion prefer to substitute Fe3+ ions located in the octahedral site. Superparamagnetic state was observed in the Mossbauer spectra of the samples with Ga content >0.5. The decrease of the magnetic hyperfine field with gallium concentration was explained on the basis of supertransferred hyperfine interaction. A semiconducting behavior was inferred for all samples and the conductivity values were found to decrease with increasing the Ga content. The conduction mechanism in the spinel ferrite compounds was explained in terms of the hopping conduction process. The dielectric constant measured as a function of frequency and temperature was found to be dependent on the Ga concentration. The determined transition temperature was found to decrease with increasing Ga content. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.