Effect of diamagnetic substitution on the structural, electrical and magnetic properties of CoFe2O4

Polycrystalline samples with the general formula Col-xCdxFe2O4 (0 less than or equal to X less than or equal to 1) were synthesized by calcining the respective oxalates mixtures at 1000 degreesC for 5 h. Their structural, electrical and magnetic properties are studied using X-ray diffraction, Fourier transform infrared and Mossbauer spectroscopy, and electrical conductivity and magnetic susceptibility techniques. With cadmium ion substitution, the lattice parameter, X-ray density, oxygen parameter, inversion factor and radii of tetrahedral and octahedral sites are calculated. The Fourier transform infrared spectra showed two dominant bands in the high- and low-frequency range which are assigned to the tetrahedral and octahedral complexes, respectively. The relationship between bands position and cadmium content was also investigated. The Mossbauer spectroscopy was carried out to study the cation distribution in this system. It was found that ions at octahedral site moved to the tetrahedral site, and that this system varied from an inverse to a normal spinel structure. The temperature variation of the conductivity showed a definite kink, except for the CdFe2O4 sample, which corresponds to the ferrimagnetic to paramagnetic transitions. The effective magnetic moment of the samples and their Curie temperature were observed to decrease by the substitution effect. (C) 2004 Elsevier B.V. All rights reserved.