Electrical and Dielectrical Properties of Low-Temperature-Synthesized Nanocrystalline Mg²⁺-Substituted Cobalt Spinel Ferrite

Abstract

Nanocrystalline samples of Co _1−x Mg _x Fe ₂ O ₄ (x = 0.0, 0.25, 0.50, 0.75, and 1.0) ferrite were synthesized by wet chemical sol-gel auto combustion method. The spinel cubic phase formation of Co _1−x Mg _x Fe ₂ O ₄ ferrite samples was confirmed by X-ray diffraction (XRD) data analysis. All the Bragg planes observed in XRD pattern belong to the cubic spinel structure of ferrite. The microstructural studies were investigated through scanning electron microscopy (SEM) technique. Pellets of Co–Mg ferrite were used to study the electrical and dielectric properties. The DC electrical resistivity studies of the prepared Co _1−x Mg _x Fe ₂ O ₄ (x = 0.0–1.0) ferrite samples were carried out in the temperature range of 300–873 K using a standard two-probe method. Ferrimagnetic to paramagnetic transition temperature known as Curie temperature (T _c) for all samples was noted from resistivity data. The Curie temperature decreases linearly as concentration of magnesium content is increased. The activation energy below and above T _c was calculated. The dielectric parameters such as dielectric constant $(\varepsilon ^{\prime })$, dielectric loss $(\varepsilon ^{\prime \prime })$, and loss tangent (tan δ) were measured with frequency at room temperature in the frequency range 10 kHz to 1 MHz. The dielectric constant $(\varepsilon ^{\prime })$ measurements with increasing frequency show two peaks at room temperature of measurements for all samples under investigation. The peaks observed show compositional dependences as a function of frequency. The observed behavior in the electrical and dielectric behavior of nanocrystalline Co _1−x Mg _x Fe ₂ O ₄ spinel ferrites is discussed in this work.