Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$g$ </tex-math></inline-formula> -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.
Highlights
E LECTRODYNAMIC analysis of structures such as resonant cavities [1] or circulators [2] loaded with gyrotropic samples constitutes a contemporary research area [3]
The main systematic error source present in the described ferromagnetic linewidth measurements is primarily due to the size dependence of the magnetic energy filling factor
The resulting negative relative error is independent of ferromagnetic linewidth and increases in absolute value with increasing electrical size of the sample
Summary
E LECTRODYNAMIC analysis of structures such as resonant cavities [1] or circulators [2] loaded with gyrotropic samples constitutes a contemporary research area [3]. Resonant modes in spherical cavities concentrically loaded with magnetized gyromagnetic spheres have been analyzed using. Jerzy Krupka is with the Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, 00-662 Warsaw, Poland. Adam Nabialek and Oleksandr Chumak are with the Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland
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