This paper describes the experimental results obtained by a broadband permeability measurement method based on the full-wave electromagnetic (EM) analysis of a non-reciprocal transmission line. The method offers a new experimental tool for measuring the broadband dynamic behavior of ferrites whatever their magnetization state. The methodology and experimental setup are presented with the aim of extracting both the permittivity and the two components (diagonal μ and off-diagonal κ) of the permeability tensor. Experimental data on commercial ferrites set in different magnetization states are presented and discussed. Furthermore, this method opens perspectives for the determination of other useful magnetic parameters such as resonance linewidth ΔH. This quantity can be then measured at different frequencies, where conventional resonant methods give a value at a fixed frequency.

A data processing program based on a full-wave electromagnetic (EM) analysis of a non-reciprocal transmission line partially filled with a ferrite sample is presented. A predictive permeability tensor model is introduced in the Maxwell equations to allow the program to work at any magnetization state. The dispersion diagram for the first significant modes inside the ferrite loaded region of the line is obtained. The presence of magnetostatic modes generated by magnetized ferrite inside the line is verified. Using a mode matching technique, the theoretical scattering parameters (S-parameters) of the non-reciprocal transmission line are calculated. The analysis is validated by the comparison between the calculated S-parameters with those obtained with a FEM based EM simulator and the measurements at limit cases.

The variation in the permeability of a multilayered polyvinylidene fluoride/CoFeB (piezoelectric/magnetostrictive) composite material under the action of a dc voltage is demonstrated. The driven-voltage permeability is first predicted using a finite element method-based multiphysics calculation. The simulation allows us to determine a magnetic anisotropy field of 45 Oe induced in the ferromagnetic layers by the mechanical coupling between magnetostrictive and piezoelectric layers due to the applied dc voltage. A variation of 30% for the permeability of the ferromagnetic layers is then measured using a radiofrequency permeameter and under the application of a dc voltage of 15 V applied on the ferromagnetic layers, which also act as electrodes for the bias of the polyvinylidene fluoride (PVDF). An additional measurement of the trilayered structure under the application of a dc magnetic field is finally performed to evaluate the magnetic field needed to get a 30% variation in the magnetic layers permeability in order to compare this value to the one predicted by multiphysics calculation. These experimental results are in good agreement with calculations and are very encouraging for the application of the CoFeB/PVDF/CoFeB composite material to ensure the tunability of microwave devices (filters, phase shifters, antennas, etc.)

broad-band characterization method based on the junction of the full-wave analysis of a nonreciprocal strip transmission line with a predictive permeability tensor model is presented. The aim of this method is the direct measurement of the permeability tensor components spectra of magnetized thick samples, whatever their magnetization state is. The propagation constants of the dominant transverse electromagnetic (TEM) and higher order modes inside the measurement cell are obtained along with its scattering parameters (S-parameters). The apparition of magnetostatic modes and the nonreciprocal nature of the structure are probed. Procedures based on the use of this method to find accurate values of gyromagnetic resonance and the resonance line width (¿H) are proposed. The direct analysis is validated by comparison of the calculated S-parameters with those obtained with an electromagnetic field simulator based on finite element methods (FEM).

Ce travail decrit l'analyse electromagnetique (E.M.) d'une structure de propagation de type triplaque dont la section transversale est partiellement remplie du materiau magnetique anisotrope a caracteriser. L'approche theorique retenue est basee sur l'analyse modale des differentes regions de la structure et, aux discontinuites, du raccordement des champs associes a chaque mode. Une methode particuliere de recherche, en variable complexe, des racines de l'equation caracteristique a ete developpee. Les diagrammes de dispersion et les parametres S traduisant le caractere non-reciproque de la structure sont presentes. Il s'agit de la premiere etape dans la mise en œuvre d'une nouvelle technique de mesure large bande in situ (environnement E.M. reel) des composantes du tenseur de permeabilite et de la permittivite des ferrites aimantes. Des procedures basees sur cette methode de caracterisation pour trouver la larguer de raie a mi-hauteur ΔH a differentes frequences et la frequence de resonance gyromagnetique des ferrites sont decrites.