Ferromagnetic Microdisks: Novel Magnetic Particles for Biomedical Applications
V. Novosad, F. Fradin, K.S. Buchanan, K.Yu. Guslienko, V. Yefremenko, A.J. Rosengart, S.G. Guy and S.D. Bader
Argonne National Laboratories, US
biomagnetics, nanoparticles, magnetic properties
Biomagnetic technologies rely on the ability of biological substances to form supra-molecular structures when they are mixed with magnetic nanoparticles. In this report we will demonstrate how thin film growth technique combined with traditional mask-transfer lithography can offer a new concept of magnetic nanoparticles with superior properties for bio-medical application . The experimental results, micromagnetic simulations and analytical theory for small (from hundred nanometers to few microns) microdisks will be reported. This system possesses a number of unique features that are especially valuable for biomedical applications. The microdisks have zero remanence due to formation of magnetic vortices in each particle, which results in independent behavior of the assembly of disks, e.g. no agglomeration. A very high Ms can be achieved by applying relatively small magnetic fields. Furthermore, the properties of the microdisks can be tailored by choosing the appropriate geometrical aspect-ratio. Due to the resonant collective behavior of spins, there are additional possibilities for detection by using alternating current susceptibility measurements. Finally, the geometry of the disk has two distinguishable surfaces, top and bottom, that can be coated with different metal layers (thin films) during the sputtering process. Therefore, one has the unique possibility of targeted delivery of two different types of bio-molecules at once.  V. Novosad and F. Fradin, “Magnetic nano-particles for bio-medical applications”, US Patent application pending.
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Nanotech 2005 Conference Program Abstract