<p>Nanoparticles of cobalt ferrite (CoFe₂O₄) and strontium-doped cobalt ferrite (Co₁₋ₓSrₓFe₂O₄, where <i>x</i> = 0.0–0.4) were produced using a diethylamine-assisted sol-gel method, followed by calcination at 600 °C. The microstructural properties were studied through Rietveld refinement of X-ray diffraction (XRD) data, which revealed the presence of a cubic spinel phase, alongside secondary Sr-containing phases at higher doping levels. The crystallite size decreased from 41 nm (for <i>x</i> = 0.0) to 34 nm (for <i>x</i> = 0.4), indicating grain refinement due to lattice strain and limited solubility of Sr. Scanning electron microscopy (SEM) analysis revealed a homogeneous formation of nanoparticles, while Fourier-transform infrared spectroscopy (FTIR) confirmed that the spinel structure was maintained, with band shifts caused by the dopant. Magnetic studies demonstrated a significant decrease in saturation magnetization as the Sr content increased, reaching 30.27 emu/g at <i>x</i> = 0.4. This reduction is ascribed to the weakening of the effect of magnetic ions and the formation of non-magnetic secondary phases. Coercivity peaked at <i>x</i> = 0.2, indicating an optimal enhancement of magnetic anisotropy. These findings confirm the impact of Sr²⁺ doping on both microstructural and magnetic properties, signifying promising applications in spintronics, magnetic storage, and various functional ferrite-based materials.</p> Graphical Abstract <p></p>