​In the world of microelectronics, magnetic metals, which offer high permeability, are often used to improve the performance magnetic components like inductors and miniature antennas. However, magnetic metals are only effective at low frequencies. However, at high frequencies, it is necessary to break the metals’ electrical conductivity to make them both magnetic and insulating.

Researchers from Leti and LTM developed a thin-layer material made from metal nanoparticles whose magnetic properties are similar to those of the material in its solid form. To break conductivity, the researchers coated the nanoparticles with a very thin polymer film. “We came up with a subtle grafting technique that lets us control the thickness and uniformity of the polymer layer,” said one researcher. “We have filed patents for several of the film fabrication techniques.”

The magnetic nanoparticle film offers a volume charge density of more than 50%, making it a good potential replacement for metals for very-high-frequency applications. Another advantage is that the material is easier and much cheaper to deposit on wafers: spin coating can be used to spread and shape the material much like a lithography resin. The initial results are very encouraging, and the material could be a prime candidate for 5G mobile communications applications.