AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuP

Paper MI-TuP3
Surfactant Effects on the Growth of FePt Nanoparticles: Toward Core-Shell Nanomagnets

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: A.C.S. Samia, Argonne National Laboratory
Authors: A.C.S. Samia, Argonne National Laboratory
X.-M. Lin, Argonne National Laboratory
J.A. Schlueter, Argonne National Laboratory
J.S. Jiang, Argonne National Laboratory
S.D. Bader, Argonne National Laboratory
Correspondent: Click to Email
Nanosized magnetic materials offer interesting possibilities to investigate fundamental physics and create new technologies in sensors, biomedicine and data storage applications. Particularly, magnetic alloy nanoparticles have attracted great interest due to their potential in ultra high-density recording media applications. Among the different nanomaterials being developed for this application is the FePt system. The high magnetic anisotropy, good chemical stability and resistance to corrosion of this material make it an ideal candidate for permanent magnet applications. Furthermore, monodispersed FePt nanoparticles can be readily obtained from the simultaneous reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of organic ligand stabilizers. To date most synthetic work has focused on the use of oleic acid and oleyl amine as passivating surfactants. Using this surfactant combination, spherical FePt nanoparticles in the size range of 3-10 nm have been reported. As prepared, the magnetic nanoparticles are superparamagnetic and requires an annealing step to transform them to a more stable magnetic state. Here we report the effects of other surfactant systems on the particle size and growth of FePt nanoparticles. We will present the effects of oleic acid and trioctylphosphine oxide (TOPO) surfactants on the particle size, size distribution and shape of FePt nanoparticles. By gaining insights on the role of these surfactants in regulating the growth of FePt nanoparticles we are able to synthesize larger FePt nanoparticles. To overcome the superparamagnetic limitation in ferromagnetic nanoparticles we are also developing novel core-shell exchange-spring nanomagnets, which consist of hard magnetic (CoPt, FePt) and soft magnetic components (Co). Such combination results to the interaction of the two phases by exchange coupling that leads to a high magnetic energy product.