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.