Activated carbon confined Mn_0.25Fe_2.75O₄ nanocomposites embedded in PVA-PVP ferrogels for magnetic hyperthermia applications

This study reports the synthesis of Mn_0.25Fe_2.75O₄/AC nanocomposites via coprecipitation and the fabrication of PVA–PVP-based ferrogels to address the limited integration of Mn-composition control, activated-carbon-assisted dispersion, and magnetothermal evaluation in ferrite-based systems for tunable magnetic heating and hyperthermia-related applications. Characterization was conducted using XRD, FTIR, SEM, TEM, SAXS, VSM, and magnetothermal testing at 965 Hz. XRD confirmed the spinel magnetite phase with characteristic reflections (220), (311), (400), (422), (511), and (440), alongside amorphous AC peaks at 2θ 25°–30°. Rietica refinement revealed a reduction in crystallite size from 15.95 to 3.66 nm and crystallinity from 76.45 to 56.45% after AC incorporation. FTIR spectra identified Fe–O vibrations at 430 cm⁻¹ and 651 cm⁻¹. The composite exhibited 67.34% porosity, while SAXS analysis indicated particle sizes of μ₁ = 2.51 nm and μ₂ = 6.23 nm. VSM results showed decreased saturation magnetization (Ms) from 6.72 to 2.72 emu/g and coercivity (Hc) from 92.45 to 4.12, indicating enhanced magnetic softness. Magnetothermal evaluation showed Tmax of 71.93 °C and SAR of 34.38 W/g for Mn_0.25Fe_2.75O₄, and 65.5 °C and 31.51 W/g for Mn_0.25Fe_2.75O₄/AC. The ferrogel exhibited improved performance with increasing filler (5–15%), achieving SAR of 22.93–28.42 W/g and T_max of 72.54–77.13 °C. ILP increased from 0.26 to 0.32 nH m² kg⁻¹ in gels and reached 0.39–0.36 nH m² kg⁻¹ in powders, indicating enhanced energy dissipation with filler addition despite reduced gel heating due to thermal loading and dispersion effects.