Fabrication and characterization of tunable magnetic nanocomposite materials

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Fabrication and characterization of tunable magnetic nanocomposite materials M. Dikeakos1, L.D. Tung2, T. Veres1, A. Stancu3, L. Spinu2, and F. Normandin1 1 IMI – National Research Council Canada, Boucherville, Quebec, Canada 2 AMRI, University of New Orleans, New Orleans, LA 70148, USA 3 Faculty of Physics, Al. I. Cuza University, Iasi 6600, Romania ABSTRACT Ferromagnetic nanocomposites in which magnetic nanoparticles are embedded into a polymeric matrix can replace conventional ferrites in the near future in applications such as: filters, high frequency inductors, chokes, sensors, core-shape and planar transformers, hybrid circuits and transponders. These dense magneto-dielectrics will provide a new approach in the fabrication of soft magnetic materials. In a magnetic/polymeric nanocomposite solid, the resistivity can be drastically increased, leading to significantly reduced eddy-current losses. In addition, the coupling between neighbouring magnetic nanoparticles results in much better soft magnetic properties at high frequencies than those of conventional bulk materials or ferrites. In order to study the influence of dipolar interactions between ferritic nanoparticles, samples of varying ferritic density were prepared. A polymeric binder (pre-swollen in toluene) was added to the nanoparticles, which were then cold-pressed using a standard compaction method. Characterization of the materials was carried out by means of x-ray diffractometry, electron microscopy, magnetometry, and high-frequency complex permeability measurements. Initial results show that tunable static and dynamic magnetic properties of the nanocomposite materials may be achievable.

INTRODUCTION Development of new materials and their understanding at ever-increasingly smaller length scales is at the root of progress in the materials research industry [1 – 3]. Rapid advances in information, telecommunication, and energy technologies coupled with the need to reduce the size and cost of devices drive this search. In particular, smaller and inexpensive power converters for portable/wireless devices are required for integration into silicon IC circuitry working at GHz frequencies; conventional ferrite-based field amplifying components are ineffective. Suitability requirements of magnetic material for high-frequency applications entail a high saturation magnetization, combined with a low coercivity and a small (but finite) anisotropy field. In addition, the material should have a high electrical resistivity to reduce eddy-current induction. None of the existing bulk magnetic alloys satisfies these requirements for ultra-high frequency operations. As such, nano-scale materials for magnetic applications have become the focus of the scientific community [5 – 7]. Nanostructured magnetic materials exhibit properties stemming from the intrinsic character of the particles and the interactions between the particles [8 – 12]. These magnetic properties often differ from both the individual constituent atoms and the bulk crystalline counterparts. For so