Effect of cobalt substitution on the properties of nickel–copper ferrite

Abstract

Cobalt-substituted nickel–copper ferrite samples having the chemical formulaNi0.95−xCoxCu0.05Fe2O4,where x varies as 0.01, 0.02 and 0.03, were prepared by the standard double sintering ceramictechnique. The formation of the ferrite phase was confirmed by x-ray diffraction (XRD)studies. Resistivity and thermo-emf variation with temperature were studied in thetemperature range from room temperature to 773 K as a function of cobalt content. As thecobalt content increases, the resistivity of the ferrites decreases. AC conductivitymeasurements made in the frequency range 100 Hz–1 MHz show that conduction in theseferrites is due to small polaron hopping. The dielectric constant and loss tangent(tanδ) were measured at room temperature as a function of frequency in the range 20 Hz to1 MHz. The room-temperature dielectric measurements show dispersion behaviourwith increasing frequency. To understand the conduction mechanism, compleximpedance measurements were carried out. The variation in saturation magnetization(Ms) with variation of cobalt content is also studied.