Modeling and design of microwave devices based on ferromagnetic nanowires

As wireless communication systems are flourishing and operating frequencies
are progressively increasing, there exists nowadays a strong demand for RF
devices at millimeter wavelengths. Nonmetallic ferromagnetic materials, also
called ferrites, have found wide applications in RF technology as they possess
the combined properties of a magnetic material and an electrical insulator.
The remarkable flexibility in tailoring the magnetic properties, the very high
resistivity, price and performance considerations make ferrites the first
choice materials for microwave applications. However, the frequency range of
operation, the bandwidth, and the aptitude to be integrated in MMICs should be
improved.

In this work, a new class of magnetic materials which could overcome the main
disadvantages encountered when using ferrites in RF devices operating at
millimeter wavelengths is studied. This material, called magnetic nanowired
substrate (MNWS), is composed of an array of ferromagnetic nanowires embedded
in a polymer substrate. First, the ferromagnetic nature of nanowires yields
very high saturation magnetizations, thus operating frequencies higher than 40
GHz. Next, the nanometric wire diameter allows an easy penetration of
electromagnetic waves inside the MNWS. Moreover, due to the high aspect ratio
of nanowires the desired magnetic properties are obtained without an external
magnetic field. This leads to a considerable potential increase of the
compactness and ease of integration in MMICs. Various potential applications,
such as filters and circulators, of this new material are presented.