An improved permeameter for thin film measurements up to 6 GHz

We report a broad band technique allowing the measurement of the permeability of thin ferromagnetic films up to 6 GHz. The permeameter is based on a single coil technique. The input impedance of the loop is measured with and without the sample. The permeability is deduced from the impedance measurement using two approaches: the first one uses an equivalent electrical circuit model and the second a transmission line theory model. This leads to significant corrections compared to previous models. Calibration of the apparatus is presented using a known sample. Our two approaches are compared to the theoretical spectral permeability. The validity of the measurements is proven by showing a full spectral gyromagnetic response of a saturated magnetic sample at different fields. (C) 1999 American Institute of Physics. [S0021-8979(99)29608-9].