Fabrication of uniform half-shell magnetic nanoparticles and   microspheres with applications as magnetically modulated optical nanoprobes
  Magnetically Modulated Optical Nanoprobes (MagMOONs) are magnetic particles that indicate their angular orientation by emitting varying intensities of light for different orientations and have shown promise for a variety of applications. In this letter we describe a new method to fabricate uniform magnetic half-shell particles that can be used as MagMOONs. Cobalt was deposited onto commercially made polystyrene nanospheres and microspheres, using ultrahigh vacuum vapor deposition, producing particles with uniform size, shape and magnetic content. Additionally, the coercivity of the cobalt deposited on the nanospheres was enhanced compared to its bulk value. 
Brandon H. McNaughton, Vladimir Stoica, Jeffrey N. Anker, Roy Clarke,   and Raoul Kopelman