Novel nanomagnetic materials for high-frequency RF applications

Abstract

This paper describes leading-edge research to explore and demonstrate new and unique nanoscale magnetic composites for high-frequency RF applications. Passivated cobalt nanoparticles were chemically synthesized and dispersed in epoxy to fabricate nanocomposite thick films. The high permeability comes from enhanced coupling between the metal nanoparticles while the insulating polymer matrix prevents eddy current loss and improves stability with frequency. Test vehicles were fabricated to demonstrate integration of these composites in organic substrates and to characterize the high-frequency properties.The frequency-dependent magnetic properties in 100-500 MHz range were extracted by impedance spectroscopy. Magnetic toroids were mechanically pressed with the metalinsulator powder. By refining the processing, permeability of 2.7 was demonstrated at VHF frequencies. The loss tangent was less than 0.04 at these frequencies.The GHz frequency-dependent material characteristics of the magneto-dielectric films were extracted from cornerprobing of parallel-plate resonators and strip inductors. By engineering the composite structures at nanoscale, a combination of stable permeability of ~2 at 1-5 GHz and permittivity of 7, not previously reported, was achieved with polymer composites for antenna miniaturization. The magnetic nanomaterials with low loss, described in this paper, can benefit several other RF and power components, leading to their miniaturization and performance enhancement in emerging RF sub-systems. The metal composite structures also lead to high permittivity in the GHz frequencies which can benefit such RF components as antennas, by allowing closer impedance matching with air.

Polymer Magnetic Composite Core Based Microcoils and Microtransformers for Very High Frequency Power Applications

“…In addition, particle shape and size further influence the eddy current losses and coercivity, thereby, the overall frequency dependent magnetic response of the core [ 18 , 19 ]. These factors depend on the preparation and processing methods of the magnetic alloy powders [ 20 ].…”

Extraction of electrical properties of nanomagnetic materials through meander-shaped inductor and inverted-F antenna structures

“…The accuracy of the characterization can be improved by increasing the number of inductor samples with different resonant frequencies. The permittivity and electric loss tangent for this magnetic nanocomposite were assumed as 7 and 0.05 respectively based on the result in [3]. As discussed in Section 3, with this method, permittivity is not sensitive to resonant frequency shift.…”

“…Nanomagnetic composite materials have opened new dimensions to miniaturize the antenna size without compromising on performance [2]. Toroid shaped disks of nanomagnetic composites have been used for permeability characterization in [3] but this method is limited to a frequency of up to 1 GHz. On the other hand, various inductive resonator structures have been used to characterize the permeability [4] but these methods require complex via drilling, and via metallization by electroplating.…”

Inkjet Printed High-Q RF Inductors on Paper Substrate With Ferromagnetic Nanomaterial

“…The inductors are designed for a commercially available photo paper substrate with a thickness 220 μm. The paper substrate has a permittivity of approximately 2.9 and a loss tangent of 0.06 below 10 GHz [7]. To fabricate the inductors, four layers of Cabot CCI-300 silver nanoparticle ink are printed onto a commercially available photo paper and then cured in an oven at 150 • C for 1 h to sinter the nanoparticles together.…”