Effect of heat treatment on structural, optical and magneto-dielectric properties of Co–Cu spinel nano ferrites

Here, we have investigated the impact of heat treatment on structural, morphological, optical and magneto-dielectric properties of Co_0.5Cu_0.5Fe₂O₄ spinel nanoferrites prepared by sol–gel auto-combustion method. The prepared samples were sintered at 700, 800, and 900 °C and then characterized by XRD, FTIR, SEM, UV–Vis spectroscopy, VSM and impedance analyser techniques. The obtained XRD patterns were refined with Full Prof Suite Software which confirmed the cubic spinel structure of the prepared sample and it was observed that crystallite size increases from 38 to 44 m with increase in sintering temperature and the same is confirmed by W–H plot also. The SEM micro graphs represent the morphological features of the prepared samples and average particle size was calculated by using the imageJ software, which ranges 47–126 nm with increase in temperature. The FTIR spectra confirmed the presence of tetrahedral and octahedral sites in the prepared samples. Various optical parameters were recorded using UV–Vis spectroscopy and it was found that optical band gap energy decreased from 3.976 to 3.832 eV, whereas refractive index increased from 2.262 to 2.283, and high frequency dielectric constant varied from 5.114 to 5.210 with rise in temperature which was due to decrease in grain boundary area and porosity. The magnetic studies were carried out at room temperature using VSM and it was found that magnetic parameters get improved with increase in sintering temperature. Dielectric measurements were made by impedance analyser in a frequency range of 20 Hz to 10 MHz which were in consonance with Maxwell–Wagner polarization and Koop’s theory.