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The electromagnetic (EM) properties of shielded gyromagnetic spheres are characterized with the aid of an electrodynamic model formulated for the transverse electric (TE) modes of an isotropic sphere, in a similar way as dielectric resonators are commonly analyzed. Broadband characteristics of geometric and energy filling factors are presented. A new measure of the magnetic loss tangent is introduced which is positive despite the intrinsic permeability of the gyromagnetic medium being negative, where existing definitions yield a non-physical negative value. The sample size dependence of those quantities is also assessed. The conclusions from the analysis are applied to investigate and de-embed ferromagnetic linewidth errors which can occur in broadband measurements of magnetic garnet spheres. Magnetic anisotropy fields and the gyromagnetic $g$ -factor are also estimated from the measurement data. Experiments were performed in a two-port subwavelength cavity, covering a frequency range of up to 28 GHz. Additionally, two-port rectangular resonant cavity linewidth measurements at a few modes have been conducted. Good agreement between the two methods is found if the systematic error is accounted for. [ABSTRACT FROM AUTHOR]

Cavities that are partially filled with ferrite material provide a tunable resonance frequency by making use of the changing \mu-characteristics of ferrites when exposed to an external magnetic bias field. The concept of using either parallel or perpendicular magnetic biasing to reach a certain resonance frequency of a cavity has been known for many years. However, a cavity based on superposition of perpendicular and parallel magnetic fields to obtain improved ferrite characteristics was suggested in W. R. Smythe “Reducing ferrite tuner power loss by bias field rotation,” IEEE Trans. Nucl. Sci., vol. 30, no. 4, pp. 273–275, 1983, but to our knowledge was neither tested nor built. Such a 2-directional biasing is expected to provide a reduction in RF losses for an identical tuning range as compared with the classical 1-directional magnetic bias. We have successfully tested this theory with a measurement set-up consisting of a ferrite-filled cavity, exposed to external biases that allow the clear separation of the two orientations of superposed magnetic bias fields. The outcome is an enlargement of tuning range with high cavity Q and the possibility of fast tuning. In this paper, we describe the measurement set-up and present the tuning ranges that we attained by applying different bias schemes. [ABSTRACT FROM PUBLISHER]

Transmittance measurements on diluted barium ferrite materials in broadband millimeter-wave frequency range have been performed. The measurements have been done using free-space quasi-optical spectrometer in transverse magnetic field up to 7.5 kOe. A set of backward wave oscillators have been used as sources of high power coherent radiation tunable in 34–120 GHz frequency region. A magnetooptical approach has been employed for the separation of dielectric and magnetic effects in ferrites and simultaneous determination of complex dielectric permittivity and magnetic permeability of materials. It has been shown that a variation in the chemical composition of ferrites leads to a change in the magnetic properties and absorption of materials in the millimeter waves. [ABSTRACT FROM AUTHOR]