Facile sol–gel synthesis of trivalent Al³⁺-Gd³⁺ ions co-doped nanoscale cobalt spinel ferrite for magneto-electronic applications

The magnetic spinel ferrites nanomaterials simultaneously doped with multivalent cations have gained a lot of interest from many researchers during the last decade. Also, the doping of trivalent rare-earth ions in spinel ferrites is promising for many technological applications. Considering these facts, in this work we investigated the trivalent Al³⁺-Gd³⁺ ions co-doped cobalt ferrite nanoparticles with nominal composition as CoFe_2-2xAl_xGd_xO₄ (x = 0.00, 0.03, 0.05, 0.07, 0.10). The sol–gel auto ignition route assisted by citric acid as a chelating agent was utilized to synthesize the series of nanoparticles. The Rietveld refined X-ray diffraction (XRD) patterns were analyzed to ensure the single-phase formation of nanoparticles with spinel cubic structure. The spherical-shaped grain morphology of the nanoparticles was indicated by scanning electron microscopy (SEM) images. The elemental analysis obtained by energy dispersive X-ray analysis (EDAX) revealed stoichiometric formation of the samples along with high purity. The two prominent frequency modes analogous to the spinel ferrite structure were noted in the infrared spectra assuring the successful formation of all the samples. The soft magnetic behaviour with a lower coercivity of the prepared nanoparticles was confirmed by the vibrating sample magnetometer (VSM) technique. The DC electrical resistivity plots indicated that resistivity decreases with an increase in Al³⁺-Gd³⁺ co-doping. The dielectric studies of all the samples showed increasing behaviour with an increase in Al³⁺-Gd³⁺ co-doping. All the results suggest that the Al³⁺-Gd³⁺ co-doped cobalt ferrite nanoparticles can be useful for real-world applications, specifically in nanoelectronics devices.