Permittivity model for ferromagnetic nanowired substrates

This letter presents the influence of ferromagnetic nanowires on permittivity and losses on a so-filled membrane. For this purpose a theoretical permittivity model has been developed by considering geometrical parameters of the substrate such as the porosity of the membrane and the height of the nanowires. It has been validated by microstrip line measurements on a composite substrate filled with cobalt nanowires. The ferromagnetic nanowires enhance the permittivity, but give no further contribution to the losses beyond the ferromagnetic resonance. This is confirmed by measurements on a similar topology including non ferromagnetic copper nanowires.