Magnetic properties of polymer nanocomposites

Inorganic nanoparticles (NPs) dispersed within polymer matrices have been exploited for a number of applications, thanks to the interesting properties which result from the combination of inorganic components and polymers. Polymeric matrix Nanocomposite materials (NCs) containing either metallic or insulating NPs have been prepared to obtain interesting magnetic [1-4] properties for use in micro and nanoelectronics. In addition, important contributions to fundamental studies in nanoscale physics have been brought by studying those materials, such as quantum tunneling of magnetization, spin reversal mechanism in single-domain particles and quantum size effects [5–7], while we foresee advanced use of these materials for their magnetoresistance properties. In this case, a liquid ferrofluid containing an oligomer resin and a dispersion of magnetic NPs is made to polymerize by UV curing to form a solid film. Magnetite is a cheap material with a lower degree of toxicity than metallic ferromagnets and can be easily synthesized through a variety of low-cost techniques, such as the thermo-chemical route [8]. UV-curing is also a cheap technique, particularly appealing now for what concerns coatings. There a UV radiation is shone on a liquid precursor, driving some chemical modifications that allow the precursor to polymerize, producing a solid polymer having tailored physical characteristics. This process is environmentally friendly, since it is solvent-free and does not require operation at higher temperatures, since the substrate is kept at room temperature. Putting together magnetic dispersoids and polymeric matrix, it is possible to control the magnetism in the NPs by modifying the matrix properties. Novel smart materials may be engineered, traducing a certain stimulus into a dramatic variation of some physical properties, such as magnetization.