Measurement of the high-frequency complex permittivity and conductivity of magnetic fluids

Measurements of the permittivity, epsilon(w) = iepsilon"(w) - and conductivity, sigma(w) = wepsilon(0)epsilon"(w), of two ferrofluid samples of ferrite particles in a hydrocarbon carrier, isopar M, over the frequency range 0.1-6 GHz are presented. It is shown that the sample with the highest concentration of particles has the highest permittivity and by means of profile fitting it is demonstrated, for the first time, that sigma(w) has a Debye-type profile. The frequency limitation of the used measurement technique is highlighted and a possible alternative technique capable of measuring in the 20-30 GHz region is presented. (C) 2002 Elsevier Science B.V. All rights reserved.