Microwave permeability spectra of ferromagnetic thin films over a wide range of temperatures

Ferromagnetic materials are of great interest today for high frequency applications in microelectronics (M-RAMs, planar inductors, etc.) or magnetic recording systems, taking advantage of the high levels of saturation magnetization of ferromagnetics. We are presenting a setup permitting permeability measurements from 10 MHz up to 6 GHz in the 77–400 K temperature range. An existing single-coil perturbation technique is modified to allow precise and accurate microwave measurements. An experimental validation of the technique is performed. Measurements on a CoFeSiB thin film are presented. The clear effect of the temperature on the whole permeability spectra is shown for soft ferromagnetic thin films, including CoNbZr.