Permeability Characterization of Ferromagnetic Nanowires Arrays From Transmission-Line Measurements

A broad-band transmission-line technique suitable for measuring magnetic and dielectric parameters of ferromagnetic nanowire arrays is discussed. Complex permittivity and permeability are obtained from analytical equations applied to S-parameter measurements of a coplanar line propagating the dominant mode. Measurements were made on crystalline Co and an amorphous alloy (Co₉₄Fe₅B₁) in the 0.05-40 GHz frequency range. The particular geometrical and electromagnetic properties of ferromagnetic nanowire arrays offer good stopband performances in the frequency range of 12-40 GHz, which cannot by achieved by classical microwave materials. Our results indicate that ferromagnetic nanowire arrays could have important technological applications for microwave devices, such as variable attenuators, phase shifters, modulators, stop-band filters and power absorbing terminals.