Fe1-yO nanoparticles:: Organometallic synthesis and magnetic properties

Non-stoichiometric wustite particles (Fe1-yO) are synthesized using the controlled room-temperature hydrolysis of the organometallic precursor {Fe[N(SiMe3)(2)](2)}. Particles stabilized by hexadecylamine with a diameter of similar to 5 nm are obtained. For such small nanoparticles, a distorted crystallographic structure is evidenced by wide-angle X-ray scattering at room temperature and reported for the first time. The study of the magnetic properties indicates that these particles are composed of an antiferromagnetic core surrounded by a ferromagnetic shell. According to the Neel theory, we demonstrate that this shell consists of 1.5% of Fe3+ ions ferromognetically coupled with Fe2+ ions.