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We compare the diagonal [micro] and off-diagonal [kappa] permeability tensor components of magnetized polycrystalline ferrites given by the theoretical model of Gelin and Berthou with experimental ones at microwave frequencies. We used a broad-band and noniterative measurement technique recently developed within our research group. Whatever the ferrite magnetization state is, simulated and measured [micro] and [kappa] points agree well. This study provides an experimental validation of the Gelin--Berthou model. Moreover, by using this characterization method, we show how the measurement of the magnetic properties can be affected by the size of the ferrite sample under test. Index Terms--Anisotropic media, demagnetizing fields, ferrites, permeability, scattering parameters.

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 μ, κ 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 μ and κ analytically from the S parameters. The theoretical approach used to calculate μ and κ 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 μ and κ data for polycrystalline ferrites and ferrimagnetic or ferromagnetic loaded composites provides an experimental validation of the model. [ABSTRACT FROM AUTHOR]

The permeability spectra of composite magnetic materials (NiZn ferrite composites and YIG composites) has been experimentally studied on a wide range in magnetic load C. The resonance frequency decreases with the increasing magnetic load of the mixture. This is attributed to the fading of the magnetic pole on the surface of the magnetic inclusions. A theory is developed which is intended to give an expression for the gyroresonance frequency of magnetic composites in their unsaturated magnetic state. It fits the experimental data over its full range of volume fraction C without any corrective factors. The proposed relation, which is an extension of the Kittel’s expression for the resonance frequency of a saturated body, points out a noteworthy close link between the concept of reciprocity and the one of demagnetization. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This paper describes a microwave measurement technique enabling the automatic and broad-band determination of the complex permeability tensor components, μ, κ of magnetized materials. The method is applicable to ferrites, as well as magnetic composite materials. The measurement cell is composed of a nonreciprocal strip transmission line partly filled with the sample that is to be characterized. The data-processing program based on a quasi-static approach is valid whatever the magnetization state of the material is from the total demagnetization state to the saturation. The scattering matrix of the cell is measured in a wide frequency range (130 MHz-6 GHz) with a network analyzer setup. The stripline is set in the air gap of an electromagnet to magnetize the material. The electromagnetic parameters of the sample under test are deduced from the scattering matrix using analytical relations. General equations for μ and κ are proposed. Some measurements of magnetized ferrites are reported and compared with values predicted by Polder's relations to validate the technique in the saturation state. To our knowledge, this is the first noniterative measurement method giving μ and κ simultaneously in a wide range of frequency. [ABSTRACT FROM AUTHOR]

Presents a physical model of the properties of polycrystalline ferrites below magnetic saturation. Characterization of properties through permeability tensor as functions of magnetization states, anisotropy field and frequency; Homogeneity of medium through medium approximation; Comparison of results for different states with empirical formulations of permeability tensor components.

Develops a nonreciprocal rectangular waveguide cell to provide a broad-band method for measuring the complex permeability tensor components of magnetized ferrites. Utilization of a network analyzer setup; Measurement of cell scattering parameters; Computation of complex permittivity from a data-processing program.

Describes a broad-band characterization method for measuring the complex permeability tensor components and complex scalar permittivity of magnetized ferrities. Anisotropic media; Microwave measurements; Permeability measurement; Waveguide discontinuities.

Presents information on a study which determined the permeability and permittivity of magnetic and dielectric thin films using a microstrip line. Selection of the measurement cell; Description of the method; Thin-film characterization; Conclusions.

Presents a study which proposed a measurement method that permits the determination of the complex permeability and permittivity of rectangular samples of various thickness. Electromagnetic analysis of the cell; Experimental results; Conclusion.