Ferromagnetic relaxation in yttrium-iron garnet and the relation to applications

Ferromagnetic relaxation measurements in single-crystal yttrium-iron garnet (YIG) are given over the range of 4.2° to 300°K. This is a report on the present status of YIG in which care has been taken to remove the extraneous rare-earth impurity ions and ferrous impurity ions. The measurements are reported in terms of the linewidth, ΔHk→0, of long-wavelength spin waves, which has been found to be approximately equal to the intrinsic linewidth of the uniform precession. ΔHk→0 is related to the spin lattice relaxation time by the following: ΔHk→0 ≃ 1/γT10. The values of ΔHk→0 were obtained using the parallel pumping technique, in which spin waves of known wavelength are generated at one-half the microwave frequency. A discussion is given of the usefulness of YIG in low-frequency microwave devices, low-temperature microwave power limiters and the Denton ferromagnetic amplifier.