Magnetodynamic Study of Spin Resonances in Cylindrical and Spherical YIG Samples

Rigorous magnetodynamic (MD) study presented in this paper reveals what seems to be the real nature of ferromagnetic resonances occurring in gyromagnetic samples situated in larger resonant cavities. Experiments were performed with cylindrical and spherical YIG samples inserted into either cylindrical dielectric resonator or typical rectangular cavity. It is shown that the dominant mode present in the YIG sample, which was identified as the HE
₁₁₁
⁺
mode, satisfies the magnetic plasmon resonance condition defined by the effective permeability μ
_r
≈ -1 for cylindrical samples or μ
_r
≈ -2 for spherical samples. Experiments confirmed the existence of surface resonances, identified as magnetic plasmons, and volume resonances. Comparison between the MD model, the quasimagnetostatic model, and the perturbation theory was performed and limitations of the approximate approaches are shown.