Co-based magnetic nanostructured material for high frequency applications

The RF circuits are difficult to be miniaturized without compromises concerning the technical performances. The inductors and antennas are the major constraints for systems miniaturization, due to the lack of magnetic materials with adequate high frequency properties. The paper presents novel Co-based magnetic nanostructured materials, with improved characteristics which recommend them as potential candidates for transformers and inductors in electronic components: higher level for saturation magnetisation and electric resistivity in comparison with commercial ferrites. The magnetic nanocomposites are prepared by sol-gel route and consist on Co magnetic nanocrystallites, arranged in a crystalline matrix (silicates, for example). The main physical characteristics of the Co/SiO2 nanopowders are developed after appropriate calcination and annealing, being dependent on the SiO2 amount and on the thermal treatment parameters: saturation magnetisation Ms = 81.7 – 130.4 emu/g, coercivity Hc = 21.7 – 26.9 kA/m (273 - 338 Oe) and increased resistivities for the sintered samples, due to the presence of the SiO2 layers.