Study of electronic structure and dielectric properties of Gd-doped cobalt nanoferrites

The current article explores the dielectric and electronic properties of cobalt ferrite nanoparticles with Gd substitution in a series CoGdxFe2-xO4 (0 <= x <= 0.1, in step x = 0.02) synthesized by the sol-gel self-combustion way. All the samples were studied with Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and impedance (dielectric) analyzer. One absorption band (upsilon(1)) was observed in FTIR measurements, which is the characteristic feature of spinel nanoferrites in fcc type structure. The presence of active Raman modes in Raman spectra at room temperature demonstrated single phase formation of cobalt nanoferrites with metallic-metallic and metallic-oxygen bonding vibrations in the tetrahedral and octahedral sites. XPS data analysis confirmed phase purity and revealed incorporation of Gd ion in the spinel fcc lattice. The valence states of Fe, Co & Gd atoms in all these nanoparticles are found as Fe3+, Co2+, & Gd3+. The dielectric constant and dielectric loss are measured in a broad frequency range of 100 Hz to 120 MHz. The dielectric constant reduces with a rise in Gd concentration and frequency. This study reveals that electronic and dielectric properties could be effectively tuned by varying concentrations of gadolinium in cobalt ferrite nanoparticles.