Ferrimagnetic Resonance in a Single-Crystal Disk of Yttrium Iron Garnet

The use of a disk instead of a sphere for the investigation of the uniform mode is discussed briefly. The discussion and the experiments are restricted to a disk with the dc field perpendicular to the plane, and to a single-crystal sample of YIG. Resonance measurements have been carried out on a disk 0.157 cm in diam and 0.0085 cm in thickness. The linewidth and saturation curve were determined in a shorted coaxial line by detecting changes in VSWR with a slotted line and probe. The frequency was 1980 Mc. The linewidth was (0.78±0.05) oe, and the line shape appeared to be Lorentzian. The critical rf field for saturation was found to be ${\text{(5.2±0.3)×10}}^{\text{−3}}\hspace{0.17em}\mathrm{oe}$ by extrapolation of the ${\text{1/h}}_{\mathrm{rf}}$ portion of the saturation curve. The resultant linewidth of the unstable z-directed spin wave 0.08 oe. This is 20 times smaller than the value reported for a sphere at 6200 Mc.