Superparamagnetic behavior and AC-losses in NiFe2O4 nanoparticles

• Nanosized particles of the NiFe2O4 compound for medical application.
• Preparation from nonaqueous solution using diethylene glycol as solvent.
• Particles with a narrow size distribution (mainly 3–6 nm) are synthesized.
• Powders prepared are superparamagnetic at 300 K.
• Magnetic susceptibility and specific loss power are sensitive to particle size.

Crystallographic, microstructural and magnetic properties of NiFe2O4 nanoparticles synthesized by precipitation from nonaqueous solutions have been studied in the work. The transmission electron microscopy studies reveal particle sizes ∼5 nm for the as-prepared particles which increase up to ∼20 nm upon annealing at 500 °C. Quasistatic magnetic measurements show superparamagnetic behavior with blocking temperature below room temperature for both the as-prepared and annealed particles. Characteristic magnetic parameters of the particles including average magnetic moment of an individual nanoparticle and effective anisotropy constant have been determined. The specific loss power which is released on the exposure of an ensemble of synthesized particles to an electromagnetic field is calculated and measured experimentally.

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