Resonance in a ferromagnetic sphere, known in the body of literature as the mode of uniform precession, has recently been proven to be magnetic plasmon resonance (MPR). This finding has prompted research which is presented in this paper on the relation between the Q-factor at the MPR and the ferromagnetic resonance (FMR) linewidth ΔH, which is a parameter of magnetized gyromagnetic materials. It is proven in this paper that ΔH can be unequivocally determined from the Q-factor measured at the MPR, if all losses in the resonance system are properly accounted for. It can be undertaken through a rigorous but simple electrodynamic study involving the transcendental equation, as proposed in this paper. The present study also reveals that electric losses have a substantially reduced impact on ΔH due to the large magnetic to electric energy storage ratio at the MPR. Theoretical results are supported by measurements of the Q-factors on a monocrystalline yttrium iron garnet (YIG) sphere.

Co2Fe0.4Mn0.6Si (CFMS) and Co2FeGa0.5Ge0.5 (CFGG) Heusler alloys are among the most promising thin film materials for spintronic devices due to a high spin polarization, low magnetic damping and giant/tunneling magnetoresistance ratios. Despite numerous investigations of Heusler alloys magnetic properties performed up to now, magnetoelastic effects in these materials remain not fully understood; due to quite rare studies of correlations between magnetoelastic and other magnetic properties, such as magnetic dissipation or magnetic anisotropy. In this research we have investigated epitaxial CFMS and CFGG Heusler alloys thin films of thickness in the range of 15–50 nm. We have determined the magnetoelastic tensor components and magnetic damping parameters as a function of the magnetic layer thickness. Magnetic damping measurements revealed the existence of non-Gilbert dissipation related contributions, including two-magnon scattering and spin pumping phenomena. Magnetoelastic constant B11 values and the effective magnetic damping parameter αeff values were found to be in the range of − 6 to 30 × 106 erg/cm3 and between 1 and 12 × 10–3, respectively. The values of saturation magnetostriction λS for CFMS Heusler alloy thin films were also obtained using the strain modulated ferromagnetic resonance technique. The correlation between αeff and B11, depending on magnetic layer thickness was determined based on the performed investigations of the above mentioned magnetic properties.

Electrodynamic theory applied to the analysis of TE n0p mode resonances in ferromagnetic spheres placed either in metallic cavities or in the free space is compared with Walker-Fletcher's theory of so-called magnetostatic modes. The influence of the diameter of the sample, its permittivity and the permittivity of the surrounding media on the resonance frequencies of a few modes is analyzed. It is shown that the dominant resonances are essentially related either to negative values of the diagonal component of the permeability tensor or, for clockwise circularly polarized magnetic fields, to negative effective permeability. The electrodynamic theory is used to determine the saturation magnetization (Ms) from measured TE n01 frequency differences.Measurements on different samples confirmed that Ms can be determined using an electrodynamic approach with uncertainties of the order of 2% regardless of sample sizes, metal enclosures or static magnetic field values.

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A rigorous electrodynamic approach to the modeling of ferromagnetic resonance (FMR) in ferrimagnetic films of arbitrary thickness placed in a rectangular microwave cavity is presented in this letter. It is shown that the coupling of the cavity mode with the FMR mode of an in-plane magnetized ferrimagnetic film occurs when the real part of its intrinsic diagonal permeability component m approaches zero. The obtained theoretical prediction of frequency vs. magnetic bias is confirmed by experiments performed on a 3 mm thin thin yttrium iron garnet (YIG) layer grown on a 500 mm thick gadolinium gallium garnet (GGG) substrate for both even and odd cavity modes. It is also shown that the proposed rigorous electrodynamic approach agrees well with perturbation theory in the high damping regime, however, leads to qualitatively different conclusions for low damping. Finally, it is demonstrated that the experimentally observed higher-order FMR modes can be attributed to the longitudinal modes distributed across the thickness of the film at frequencies corresponding to negative values of m approaching zero. This letter paves the way for further study of, among others, the magnonmicrowave photon coupling strength and the development of ferromagnetic linewidth characterization methods.Strong coupling between cavity modes and magnetic samples, also known as the hybrid CMP (cavity-magnon-polariton) mode, currently represents a highly active research area [1] that can lead to applications in quantum information processing. If a microwave cavity is loaded with a magnetic sample, hybrid CMP modes can occur when the cavity mode and ferromagnetic resonance (FMR) mode couple. [2,3] The coupling takes place for samples that are sufficiently large with respect to the cavity and whose ferromagnetic linewidth ΔH is narrow enough. Many existing descriptions of this phenomenon utilize quantum mechanics [3,4] in the macrospin formalism. [5] A few involve electrodynamics, [6,7] however, to the authors' knowledge all of these methods have their limitations as compared to the rigorous but straightforward approach discussed in this letter. The presented method concerns not the more common extrinsic [8] but intrinsic permeability tensor of the ferromagnet [9] related to internal sample fields, with the relationship between the internal and external fields imposed by boundary conditions for electromagnetic fields. The diagonal and offdiagonal components m and κ of the relative tensor permeability of a saturated ferromagnet in the low magnetic loss regime (α ( 1) can be conveniently expressed as follows: [9] where α is the Gilbert damping factor, H r ¼ H= 4πM s ð Þis the relative internal magnetic bias,ŵ ¼f = γ4πM s ð Þis the relative; 4πM s is the saturation magnetization of the sample, γ % 2:8 MHz Oe À1 is the gyromagnetic ratio, and Q 0 is the unloaded quality factor of the resonant system including the sample. In this work, a model of an in-plane (IP)-magnetized [111] yttrium iron garnet (YIG) layer grown on a gadolinium gallium garnet (GGG) su...