Microwave Power‐Tuned Synthesis of Magnetic Nanoparticles: Correlation Between Structural Ordering, Magnetic Properties, and Hyperthermia Performance

ABSTRACT Achieving precise control over particle size, phase purity, and magnetic response remains a major challenge in synthesizing Fe 3 O 4 nanoparticles for magnetic hyperthermia. Here, Fe 3 O 4 nanoparticles were synthesized by a microwave‐assisted co‐precipitation method at microwave powers between 180 and 900 W to investigate the influence of power on structural, magnetic, and hyperthermia properties. Synthesis was completed within 15 min, substantially reducing processing time compared with conventional methods. Rietveld refinement revealed that powers above 450 W promoted secondary Fe 2 O 3 formation, reaching approximately 30 wt% at 540–720 W before decreasing at 900 W because of oxygen depletion during vigorous boiling, consistent with O 1s XPS analysis. Electron microscopy showed a transition from spherical agglomerates to faceted, plate‐like structures with increasing power. Magnetic characterization, including ZFC/FC measurements from 5–300 K, indicated SPM‐like behavior approaching the superparamagnetic regime near room temperature. The 450 W sample (IO3) exhibited the highest saturation magnetization (68.00 emu g − 1 ) and the lowest lattice strain. Hyperthermia studies showed that 3 mg mL − 1 nanoparticle suspensions reached 42°C within 600 s, with IO3 exhibiting the highest SAR (109.32 W g − 1 ) and ILP (2.13 nH m 2 kg − 1 ), identifying 450 W as the optimum synthesis power.