Influence of Cr3+ ion on the structural, ac conductivity and magnetic properties of nanocrystalline Ni–Mg ferrite

Nanocrystalline samples of the Ni–Mg ferrite with the general chemical formula Ni0.5Mg0.5CrxFe2−xO4 (0≤x≤1.0, in the step of 0.2) have been synthesized by the citrate-gel auto combustion route. The synthesized samples were characterized by means of XRD, EDAX, FT-IR, UV–visible, dielectric, ac impedance spectroscopy, and AFM, SEM, TEM and FC/ZFC measurements. X-ray powder diffraction of all the samples were carried out at room temperature to check the formation of the required products and structural related properties. The elemental analysis as obtained from the EDAX measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. IR studies confirm two main absorption bands in the frequency range of 400–800 cm−1, arising due to the tetrahedral (A) and octahedral [B] stretching vibrations. Impedance spectroscopy techniques have been used to study the effect of grain and grain boundary on the electrical properties of the prepared samples. The samples were zero field cooled (ZFC) to 100 K. Typical blocking temperature effects were observed below the temperature of about 129 K. The obtained results have been discussed so as to bring out the role of chromium substitution on the structural, dielectric and magnetic properties of Ni–Mg ferrites.