Ferromagnetic resonance in ruthenium‐doped yttrium–iron garnet

The ferromagnetic‐resonance field and the linewidth of ruthenium‐doped yttrium‐iron garnet (YIG) have been studied at 9.25 GHz in the temperature range 4.2 to 300°K. The behaviour of the resonance field can be well explained with the single‐ion model which yields the ratio of trigonal field to spin‐orbit coupling ν/ξ = −0.6 and the g‐factor times the exchange field gHe = 1.04 × 107 Oe. The linewidth can be qualitatively interpreted in terms of the longitudinal relaxation model, which requires a very short relaxation time of about 10−13 s.