Nanoparticles of CoFe₂O₄ and CoIn_0.15Fe_1.85O₄ ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In³⁺ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ε′) and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ε′, tan δ, and ac conductivity (σ_ac) with frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general and the hopping of charge between Fe²⁺ and Fe³⁺ as well as between Co²⁺ and Co³⁺ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.

We propose Mg doping in zinc oxide (ZnO) films for realizing wider optical bandgap in highly c-axis oriented Zn_1−xMg_xO (0 ≤ x ≤ 0.3) thin films. A remarkable enhancement of 25% in the bandgap by 30% Mg doping was achieved. The bandgap was tuned between 3.25 eV (ZnO) and 4.06 eV (Zn_0.7Mg_0.3O), which was further confirmed by density functional theory based wien2k simulation employing a combined generalized gradient approximation with scissor corrections. The change of stress and crystallite size in these films were found to be the causes for the observed blueshift in the bandgap.