Structural, Optical and Magnetic Properties of Gd3+ Substituted Ni0.7Zn0.3Fe2O4 Ferrites

<title>Abstract</title> <p> For the last several decades, ferrites have been widely studied due to their unique magnetic properties and their potential applications in magnetic hyperthermia and targeted drug delivery. The current study explores the structural, optical, and magnetic properties of Gd-substituted nickel–zinc ferrites at the nanoscale. Ni _0.7 Zn _0.3 Gd _x Fe _2−x O ₄ (where <italic>x</italic>  = 0, 0.005, 0.010, 0.015, 0.020, and 0.025) compounds were synthesized through a citric-acid-assisted sol-gel self-ignition method. HRTEM images confirm that the particles of synthesized compounds are spherical in shape, with particle sizes ranging from 33–45 nm. SAED patterns confirmed the stabilization of the cubic spinel phase with no apparent change in lattice dimensions. A distinct blue shift of the absorption edge in UV–Visible spectra with increasing Gd ³⁺ concentration indicates an increase in the optical band gap. Photoluminescent spectra confirm a marginal decrease in intensity of the peaks with increasing Gd concentration. Gd substitution also induces soft magnetic characteristic features in all the compounds with an S-type hysteresis profile. ESR spectra further revealed enhanced spin-coherence and narrower peak-to-peak line widths upon Gd³⁺ incorporation, suggesting modified magnetic interactions. </p>