A broadband method to measure magnetic spectra of thin films

Abstract

Conventional single-port strip-line techniques to measure permeability of thin films are based on the quasistationary approximation. In this paper, wave phenomena in the measurement cell are taken into account. Particularly, the dielectric response of the sample may be accounted for and removed by the consideration of the geometry of the cell and the sample. An additional measurement with a reference sample with known constitutive parameters allows the directivity error and the frequency response error to be removed from the experimental reflectivity data; accounting for the field inhomogeneity inside the strip cell is also introduced. A proper selection of the reference sample is shown to be critical for the measurement accuracy. The measurement results may also be affected by the demagnetization of the sample. With these corrections introduced, the operating frequency range of the technique is extended up to 8GHz. The measurement results are validated by the data obtained with either standard materials or by conventional techniques.