Measurement of Magnetism in Composite Materials

This paper focuses on the measurement of the effective magnetic permeability mu_eff in composite structures built from nonmagnetic materials. Starting from recent studies of magnetism in microstructures, we present the results of a new theoretical and experimental analysis performed at frequencies below the medium frequencies. Mainly, we focus on how ldquospatial averagingrdquo can affect the estimation of the parameter mu_eff and show how expressions of mu_eff derived for a single ldquounit-cellrdquo configuration find analogy with that relevant to composite structured arrays. Finally, we show how to obtain negative values of mu_eff for composite materials in the industrial frequency range and make some remarks on how future technologies can impact on the measurement of magnetism in composite materials.