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[en] Magnetic properties of Fe3O4 and magnetic tunnel junctions with Fe3O4 bottom electrode have been investigated. Highly conductive V/Ru layers were used as an underlayer of the Fe3O4 films. The V/Ru/Fe3O4 on  out-of-plane oriented MgO single crystal substrate show an anisotropy and high squareness along [11(bar sign)0] direction, while the Fe3O4 films with an underlayer of just Ru show isotropic behavior and low squareness. X-ray diffraction shows tensile stress on Fe3O4 for V/Ru/Fe3O4 samples. The anisotropy was shown to be induced by the stress. Finally, magnetic tunnel junction stacks of MgO/V/Ru/Fe3O4/AlO/CoFe/NiFe/Ru were deposited and the magnetic tunnel junctions with a junction size ranging from 2x2 μm2 to 9x9 μm2 were fabricated by optical lithography. The junctions show magnetoresistance ratios of ∼14% and no geometrical effect due to the junction size
[en] A granular magnetic material, Co-Fe-Hf-O, has been developed-using dc pulsed magnetron reactive sputtering. The deposition rate is as high as 1.3 nm/s. The electrical and magnetic properties of Co-Fe-Hf-O film can be tuned by changing O2 during deposition. A highly resistive, magnetically soft film has been achieved in a small range of the O2/(Ar+O2) gas flow ratio. The origin of the dependence of magnetic and electrical properties of this material is studied and explained by monitoring the evolution of the film microstructure, using x-ray diffraction and transmission electron microscopy
[en] Optical observations of 100 nm metallic magnetic nanoparticles are used to study their magnetic field induced self assembly. Chains with lengths of tens of microns are observed to form within minutes at nanoparticle concentrations 1010/mL. Chain rotation and magnetophoresis are readily observed, and SEM reveals that long chains are not simple single particle filaments. Similar chains are detected for several 100 nm commercial bio-separation nanoparticles. We demonstrate the staged magnetic condensation of different types of nanoparticles into composite structures and show that magnetic chains bind to immuno-magnetically labeled cells, serving as temporary handles which allow novel magnetic cell manipulations.
[en] A microfabricated magnetic sifter has been designed and fabricated for applications in biological sample preparation. The device enables high-throughput, high-gradient magnetic separation of magnetic nanoparticles by utilizing columnar fluid flow through a dense array (∼5000/mm2) of micropatterned slots in a magnetically soft membrane. The potential of the sifter for separation of magnetic nanoparticles conjugated with capture antibodies is demonstrated through quantitative separation experiments with CD138-labeled MACS nanoparticles. Capture efficiencies ranging from 28% to 37% and elution efficiencies greater than 73% were measured for a single pass through the sifter.
[en] We present proof-of-concept experiments and modeling towards a high-sensitivity magnetic microarray which 'tags' a DNA fragment (or other biological samples) with a high-moment magnetic nanoparticle (NanoTag), which is in turn detected by a high-sensitivity spin valve (SV) or magnetic tunnel junction (MTJ) detector array. The detector can count the number of magnetic tags with a resolution of 1-20 magnetic NanoTags, potentially counting individual biomolecules