Permeability tensor of magnetized ferrites at microwave frequencies:: A comparison between theory and experiment

The permeability tensor of partially magnetized ferrites or composite materials, given by a recent mathematical model developed in our laboratory, is compared with measured one over the 50 MHz-6 GHz frequency range. The characterization method used to measure the tensor components mu, kappa is based on the broadband determination of the S parameters of a nonreciprocal strip transmission line. The quasistatic electromagnetic analysis of the measurement cell permits the expression of mu and kappa analytically from the S parameters. The theoretical approach used to calculate mu and kappa is based on the extension of the effective medium approximation (EMA) to the case of anisotropic magnetic materials. The interactions between magnetic domains and the hysteresis phenomenon are taken into account in our calculations. The good agreement observed between simulated and measured mu and kappa data for polycrystalline ferrites and ferrimagnetic or ferromagnetic loaded composites provides an experimental validation of the model. (C) 2003 American Institute of Physics.