Fabrication of Magnetically Half-Coated Nanoparticles Using Molecular Beam Deposition

The top-down approach of building nanodevices can be combined with the bottom-up to create half-coated nanoparticles with well controlled magnetic, optical, electronic, and chemical properties. A type of half-coated nanoparticle particle that utilizes both optical and magnetic control is Magnetically Modulated Optical Nanoprobes (MagMOONs) (JN Anker, and R Kopelman, Appl. Phys. Lett., 82, 1102-1104 (2003).). MagMOONs emit modulated fluorescence or reflection intensities when externally manipulated by a magnetic field. We have fabricated functional MagMOONs by coating a thin layer of polycrystalline cobalt onto micro and nanospheres using molecular beam deposition (MBD). Additionally, vectorial magneto-optical Kerr effect was used to study the magnetization reversal of the coated spheres supported by a substrate. Hysteresis loop variations associated with the sphere size changes are observed and compared with the case of planar deposited films.