Techniques of microwave permeability characterization for thin films

We review the microwave methods to characterize the material properties, including the established and the emerging techniques in material characterization, especially the permeability spectra of the magnetic thin films. Almost all aspects of the microwave techniques for characterizing the permeability of thin films at microwave frequencies, including the new methods developed by our group, are presented. Firstly, the introduction part is presented. Secondly, the coaxial-line with transmission/reflection methods and the pickup coil with electromagnetic induction method are presented. Thirdly, the most widely used shorted microstrip technique is discussed in detail by the equivalent circuit method, transmission line method, and electromagnetic induction method. Fourthly, the coplanar waveguide method and the near-field probe method are also introduced. Finally, the high temperature permeability characterization by using the shorted microstrip line, the near-field microwave probe, and the shorted microstrip line probe are described in detail. This paper may be useful for researchers or engineers who will build up such measurement fixture to make full use of the existing methods or to develop original methods to meet the requirements for ever-rising measurements.