Effect of annealing on phase formation, microstructure and magnetic properties of MgFe2O4 nanoparticles for hyperthermia
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In this study the effect of annealing time is confirmed to alter the morphology (shape and size) of magnesium ferrite nanoparticles (MgFe2O4) synthesized by autoclave route, employing ferric and magnesium nitrate salts as precursors. Annealing was applied at 1000 °C for different durations (2, 30 and 60 h) and Rietveld refinements of X-ray diffraction patterns confirm the formation of pure spinel phase and show that the annealing time has a dominant effect on the crystallite size as it increases from 29 up to 89 nm for 2 to 60 h, respectively. Scanning electron microscopy observations confirm that longer annealing time enhances particle growth, in agreement with the crystallite size obtained by X-ray diffraction analysis. Room temperature magnetic measurements reveal a ferromagnetic behavior with a saturation magnetization (Ms) ranging from 25.84 emu/g for annealing at 2h and 29.49 emu/g at 60 h. Self-heating characteristics under an alternating current (AC) magnetic field of 17mT and frequency of 331 kHz were investigated for hyperthermia applications using Magnetherm from Nanotherics. Temperature-time curves indicate that the as-prepared MgFe2O4 nanoparticles show a considerable heating rate, with a maximum temperature of 48 °C in a very short period of time of 15 min and specific absorption rate (SAR) of 19.23 W/g, when annealed for 60 h.