Accurate Characterization of Both Thin and Thick Magnetic Films Using a Shorted Microstrip

We report an improvement on a single coil technique allowing the measurement up to 6 GHz of the permeability of magnetic films, both thin and thick. The permeability is deduced from two impedance measurements, with and without a saturating magnetic field. An equivalent electrical circuit model is used to retrieve the impedance solely due to the film from the measured one. The improvement discussed in this paper is obtained by considering a single coil as a shorted microstrip and proceeding to a transmission line analysis. From it, we obtain an expression for the scaling coefficient (SC) common to thin film techniques. We prove its consistency by comparing it favorably with SCs determined from a thin film reference sample. Our technique is therefore no longer restricted by the choice of reference samples. We illustrate this by measuring magnetic films hundreds of micrometers thick and comparing the results with a coaxial line measurement.