Structural Modification and Enhanced Ferrimagnetism of Zn/Cr Co‐Substituted CuFe₂O₄ Spinels through Sol–Gel Synthesis

In this study, the impact of Zn/Cr co‐substitution on CuFe 2 O 4 spinel ferrites synthesized by the sol–gel method is investigated using various techniques. The Zn/Cr concentration is varied systematically, resulting in a phase transition from tetragonal I 4 1 / amd to cubic structure. Lattice constants show a gradual contraction as the Zn/Cr substitution level increases. UV–vis spectroscopy indicates a bandgap energy range of 1.35–2.75 eV, with the lowest energy observed for the highest Zn/Cr co‐substitution level. Magnetic characterization reveals a hard‐to‐soft phase transition, with coercivity decreasing and saturation magnetization increasing with increasing Zn/Cr content. In these results, the tunable structural, optical, and magnetic properties of CuFe 2 O 4 spinel ferrites with Zn/Cr co‐substitution are highlighted.