Magnetically uniform and tunable Janus particles

Magnetic particles serve as an important tool for a variety of biomedical applications but often lack uniformity in their magnetic responsiveness. For quantitative analysis studies, magnetic particles should ideally be monodisperse and possess uniform magnetic properties. Here we fabricate magnetically uniform Janus particles with tunable magnetic properties using a spin-coating and thermal evaporation method. The resulting 2 mu m ferromagnetic particles exhibited a 4% magnetic response variability, and the 10 mu m ferromagnetic particles exhibited a 1% size variability and an 8% magnetic response variability. Furthermore, by reducing the film thickness, the particle behavior was tuned from ferromagnetic to superparamagnetic. c 2011 American Institute of Physics. [doi:10.1063/1.3541876]