AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+NS-MoA

Paper MI+NS-MoA1
Self-assembly and Magnetism in Novel Core-shell Microspheres

Monday, November 4, 2002, 2:00 pm, Room C-205

Session: Self-Assembly and Nanomagnetism
Presenter: E.L. Bizdoaca, Halbleiterphysik und Optik, TU Braunschweig, Germany
Authors: E.L. Bizdoaca, Halbleiterphysik und Optik, TU Braunschweig, Germany
M. Spasova, Halbleiterphysik und Optik, TU Braunschweig, Germany
M. Farle, Halbleiterphysik und Optik, TU Braunschweig, Germany
Correspondent: Click to Email
We report on the fabrication and characterization of new composite core-shell particles with a defined shape, composition and multilayer shell thickness. These colloids can be produced by the layer-by-layer technique.@footnote 1@ They consist of a core of a polystyrene (PS) microsphere (640 nm diameter) coated with consecutive shells of Fe@sub 3@O@sub 4@ nanoparticles (12 nm diameter) / polyelectrolytes /Au nanoparticles (15 nm). For the formation of the gold shell Au nanoparticles encapsulated in a very thin layer of silica (2 nm) were used. Composite core-shell particles were self-assembled into 1D periodic long-chain structure (up to 600 µm) by magnetophoretic deposition.@footnote 2@ The length and separation of the chains were found to depend on the magnitude of the magnetic field and on the concentration of the water-based colloidal solution. The self-organization and the homogeneity of the colloidal coating were characterized by transmission electron and atomic force microscopy. Magnetic properties were determined by angular dependent ferromagnetic resonance (FMR) and SQUID-magnetometry between 5 and 300 K. FMR reveals long-range magnetic order at 300 K due to the dipolar coupling and an easy axis in plane, along the chains. We report a reduced magnetic moment in comparison with the magnetite bulk value. The remanence magnetization and the coercivity field (240 Oe) are not temperature dependent between 5 and 300 K. Supported by Deutsche Forschungsgemeinschaft. . @FootnoteText@ @footnote 1@ F. Caruso et al, Chem.Mater.13 (2001) 109.@footnote 2@ E. L. Bizdoaca et al, J. Magn. Magn. Mater. 240 (2002) 44.