Enhanced heating ability of Fe–Mn–Gd ferrite nanoparticles for magnetic fluid hyperthermia

This paper reveals the structural, magnetic and heating ability of citric acid coated Fe_0.3Mn_0.7Gd_xFe_2−xO₄ (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) nanocrystalline ferrites. The synthesis of Gd-doped Fe–Mn ferrite nanoparticles (NPs) is confirmed by XRD studies. Substitution of Gd³⁺ions in Fe–Mn ferrite causes the lattice constant enhancement from 8.3286 to 8.4699 Å. The cation distribution reveals that Gd³⁺ ions preferred the octahedral sites of Fe–Mn ferrite. The average crystallite size is around 10–12 nm. The Fe–Mn–Gd spinel ferrite NPs are also characterized by FTIR studies and supports its formation. The saturation magnetization increases with Gd-content, take its maximum value for x = 0.06 and drops further for higher x values. The change in saturation magnetization show a connection with the structural modifications; because of replacement of Gd³⁺ ions at the place of Fe³⁺ ions in the octahedral site (B-site), it modifies A and B sublattices superexchange interactions. The heating abilities of these nanoparticles are studied by applying different alternating magnetic fields at constant frequency 289 kHz. When referred to the Gd-content, the SAR exhibits similar variation as saturation magnetization (M_s) and anisotropy constant (K), the later being more dominant. The highest value of SAR is 640 W/g for Fe_0.3Mn_0.7Gd_0.06Fe_1.94O₄ sample under an applied field 251.4 Oe. It is seen that SAR is increased by nearly six times as compared to pristine Fe_0.3Mn_0.7Fe₂O₄ nanoparticles. The present results suggest that magnetic field controlled therapeutic temperature can be easily achieved within 1 min using such nanoparticles.