Fuel-dependent tailoring of magnetic properties in strontium ferrite nanoparticles (SrFe2O4) synthesized via gel combustion for enhanced magnetic hyperthermia performance

This study investigates the effect of fuel chemistry and oxidizer-to-fuel ratio on the synthesis of Sr–Fe–O nanoparticles by gel combustion and evaluates their magnetic properties, cytotoxicity, and magnetic hyperthermia performance. Rietveld refinement revealed a multiphase crystalline structure dominated by Fe 3 O 4 (71.4–92.6%), accompanied by different Sr-containing phases, including Sr 2 FeO 4 , Sr 5 Fe 6 O 15 , Sr 3 Fe 2 O 6 , and residual SrCO 3 , depending on fuel type and Ψ. Increasing Ψ strongly reduced the Sr 2 FeO 4 fraction, while citric acid favored the formation of Sr 5 Fe 6 O 15 and TRIS favored Sr 3 Fe 2 O 6 . These results demonstrate that fuel chemistry and oxidizer-to-fuel ratio govern not only particle size and magnetic response but also the phase-evolution pathway of the Sr–Fe–O system. Cytotoxicity tests showed cell viability above 85 % for all samples, indicating biocompatibility. Among the investigated compositions, SrAcΨ0.8 showed the best hyperthermia response, reaching 45 °C rapidly and presenting the highest SAR value.