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We describe a theoretical approach for determining the permeability tensor of polycrystalline ferrites regardless of their magnetization state. To take into account both the demagnetizing dynamic fields related to the magnetic domain and grain shapes and the magnetic interactions between adjoining domains and between adjoining grains, we transform the classical Landau-Lifschitz-Gilbert equation into a coupled two-equation system. We introduce statistical distribution laws for both the domain and grain demagnetizing coefficients into the calculation to take the domain and grain shape diversity into account and derive static vectorial quantities such as the internal magnetic dc field and magnetization in each domain that depends on the applied dc magnetic field from the Stoner-Wohlfarth hysteresis model. We compare results with those for existing models for various magnetized states. Then we apply the model to predict the permeability tensor behavior of barium hexaferrite thin film, especially in the remanent state, which is of great interest for the design of self-biased Y-junction circulators in the millimeter-wave range. [ABSTRACT FROM AUTHOR]

This paper describes a mathematical model enabling the calculation of the effective permeability tensor of heterogeneous magnetic materials set in various magnetization states. The theoretical approach we propose permits to predict the microwave behavior of unsaturated magnetic loaded composites as well as those of unsaturated polycrystalline ferrites. The model gives all the complex components of the permeability tensor in a single calculation phase whatever the magnetization state of the material is. This is useful for the computer-aided design of microwave magnetic devices. The calculation of the effective permeability tensor is carded out from a limited number of parameters: saturation magnetization, anisotropy field, damping factor, external dc field strength, concentration, and shape of the magnetic particles or domains. The model is predictive in the way that the magnetization state of the material is determined from the strength of the external dc magnetic field applied on the material. [ABSTRACT FROM AUTHOR]

Presents a study that compared the diagonal µ and off-diagonal κ permeability tensor components of magnetized polycrystalline ferrites given by a theoretical model with experimental ones at microwave frequencies. Application of a broad-band and noniterative measurement technique in determining the ferrite magnetization state; Discussion of the experimental validation of the model; Suggestions regarding the association of the model with the technique in the design of nonreciprocal and tunable planar microwave ferrite devices.

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.

Proposes a model which provides integral expressions for all magnetic permeability tensor components, that can be treated numerically without difficulties, in microwave devices. How the causal aspect that is required when numerical time-domain methods are used is provided by the model; Demonstration of the validity of the model.

Presents a study which outlines the finite-difference time-domain (FDTD) treatment of partially magnetized ferrites which are characterised by a permeability tensor model. Comparison of numerical and analytical results of study; Information on a classical FDTD model; Description of an FDTD algorithm for an unsaturated ferrite.

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.