Measurement at microwave frequencies of the magnetic properties of small quantities of powdered or diluted samples

Transmission line techniques are a convenient way to determine the electromagnetic properties of a variety of materials in the ranges of radio and microwave frequencies. Traditional methods based on the measurement of the four scattering parameters can be successfully replaced for the method presented here, in which no change in the geometry is needed, since two independent measurements are carried out, with and without an applied magnetic field. In addition, given the small size of the sample holder, the required amount of material can be drastically reduced, and allow the use of a lumped circuit model, then reducing the inherent difficulties associated with the use of distributed parameters. Even though this kind of model requires the involved wavelengths to be much larger than the size of the system, this requirement can be overcome as long as the tested materials have relative epsilon or mu lower than 100. Furthermore, the use of short-circuited transmission lines simplifies sample holding and systematizes the measurement process, which is an important target when dealing with measurements within the radio and microwave frequency ranges. (C) 2015 AIP Publishing LLC.