Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

Nanoparticles of CoFe₂O₄ and CoIn_0.15Fe_1.85O₄ ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In³⁺ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ε′) and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ε′, tan δ, and ac conductivity (σ_ac) with frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general and the hopping of charge between Fe²⁺ and Fe³⁺ as well as between Co²⁺ and Co³⁺ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.