Structure–Property Relationships in Hydrothermally Synthesized Co _1‐X Zn _X Fe ₂ O ₄ Nanocrystalline Spinel Ferrites

ABSTRACT Cobalt–zinc spinel ferrites are promising multifunctional materials due to their tunable magnetic, dielectric, and electrical properties governed by cation distribution and lattice defects. In this work, Co 1‐x Zn x Fe 2 O 4 (x = 0.1–0.9) nanocrystalline spinel ferrites were synthesized via a hydrothermal method to investigate the relationship between microstructural strain and functional properties. X‐ray diffraction confirmed the formation of a single‐phase cubic spinel structure with lattice parameters increasing from 8.329 to 8.401 Å with Zn 2 + substitution. Microstructural analysis using Scherrer, Williamson–Hall, Halder–Wagner, and size–strain plot models revealed crystallite sizes of 2–7 nm along with notable variations in lattice microstrain and defect density. Scanning electron microscopy showed agglomerated particle clusters with sizes between 167 and 311 nm, while energy dispersive x‐ray spectroscopy confirmed the presence of Fe, Co, Zn, and O without detectable impurities. Vibrating sample magnetometry measurements indicated soft magnetic behavior with saturation magnetization values ranging from 10.76 to 15.33 emu g − 1 , influenced by Zn‐induced cation redistribution and surface spin disorder. Dielectric analysis revealed strong low‐frequency permittivity and Maxwell–Wagner polarization behavior. The composition x = 0.5 exhibited optimal magnetic ordering and dielectric response, indicating potential for high‐frequency electronics and electromagnetic interference shielding applications.