Dresden 2006 – scientific programme

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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.81: Poster

Tuesday, March 28, 2006, 15:15–19:15, P1

Magnetic Co nanoparticles in solution — •Mikhail Feygenson, Klaus Pollmeier, Emmanuel Kentzinger, Wiebke Sager, and Thomas Brückel — Forschungszentrum Jülich GmbH,Institut für Festkörperforschung, Streumethoden, Leo-Brandt-Straße, 52428 Jülich, Germany

Magnetic nanoparticles are of the high current interest for both possible applications as magnetic storage materials as well fundamental research. An open question and a challenge to experiment and theory is the magnetization density distribution within single particles, which is expected to be non-uniform. Here we report progress towards the aims to determine the averaged magnetization density within single particles and the response of the ensemble to an external field. Co nanoparticles were synthesized by employing the interior of water-in-oil (w/o) microemulsions as nanoreactors. Particle size and morphology depend on the microemulsion composition and the concentrations of the reactants. To separate the particles from the microemulsion medium we used dodecanethiol and/or octadecanethiol as stabilizing ligands and re-dispersed the particles after precipitation in either hexane or toluene. The Co nanoparticles were characterized by magnetization measurements, electron microscopy and scattering experiments. The re-dispersed Co nanoparticles display a relatively high saturation field (more then 1 T) and the absence of a net magnetization at room temperature in the SQUID magnetometer. Scattering experiments (small angle X-ray and neutron scattering) are reported for the microemulsion system employed as well as for the re-dispersed nanoparticles