Impedance and DC resistivity studies on chromium substituted cobalt ferrite

Nanocrystalline chromium substituted cobalt ferrite has been prepared by the sol-gel method. XRD analysis reveals that the samples crystallize to cubic symmetry with spacegroup. Two transition temperatures (T (D) similar to 450 and T (M)similar to 600 K) have been observed from the impedance versus temperature measurement. T (D) increases with the increase in frequency due to dipole response to the frequency. T (M) is comparable with the para-ferrimagnetic transition temperature of cobalt ferrite, which is independent of frequency. This result is well supported by the temperature dependent DC resistivity measurement. The modified Debye relaxation could explain the impedance spectra of CoFe2-xCrxO4. The grain and grain boundary effect on impedance spectroscopy has been observed from Cole-Cole analysis. The ac conductivity follows Arrhenius behavior at different frequencies. All the samples exhibit the negative temperature coefficient of resistance behavior which reveals the semiconducting behavior of the material. The Mott VRH model could explain the DC electrical resistivity. Both ac impedance and DC resistivity are well co-related with each other to explain the electron transport properties in Cr substituted cobalt ferrite. The electrical transport properties could be explained by the electron hopping between different metal ions via oxygen in the material.