Abstract EN:

Magnetic nanoparticles are of great interest for hyperthermia treatment of tumours. Their efficiency depends on their size, their surface state and the material used. We realised a fundamental study of the iron nanoparticles synthesis, of their specific magnetic properties and of their hyperthermia response. A detailed analysis of theoretical models could enlighten the optimised properties (superparamagnetism/ferromagnetism transition, high saturation magnetisation MS ). Monodisperse iron nanoparticles are synthesized by the decomposition of the organometallic precursor (Fe{N[Si(CH3)3]2}2)2. The growth mechanism was studied by kinetic studies using electronic microscopy, Mössbauer spectrometry and SQuID measurements. The key role of lamellar structures and acid concentration was described. A new approach, never reported so far, based on the ripening of small iron germs was used for the first time. Particle with tuneable sizes ranging from 1. 5 to 11. 2 nm were obtained with Ms = 220 Am2. Kg-1. An increase of the anisotropic constant was reported for small particles regarding bulk iron (10 for 1. 5 nm and 3 for 5. 5 nm). Magnetic configurations have been directly imaged in 30 nm nanocubes thanks to the electronic holography technique. Micromagnetic simulations coupled with holography permit to quantitatively analyse a vortex structure in an isolated cube. A frequency adjustable electromagnet was designed. The first hyperthermia measurements are reported for superparamagnetic iron (of 5. 5 and 7. 5 nm). A ferromagnetic behaviour corresponding to Stoner-Wohlfarth model was for the first time observed for 14. 2 nm FeCo nanoparticles