Attenuation of spin waves due to four-magnon scattering

The contribution from the four-magnon exchange scattering to the parameter of dissipation of spin waves with a frequency of approximately 18GHz and wave numbers to 10 6 cm-1 has been isolated. It has been measured by the longitudinal pumping technique in an yttrium-iron garnet in the temperature range from 120 to 300 deg K. The contributions from the three- and four-magnon processes are separated: a) disregarding the temperature dependence of the magnetization Msub(0) and the exchange 'constant' D and b) considering the experimental dependences Msub(0)(T) and D(T). When the temperature dependence of the magnetization and the exchange 'constant' are taken into account, the agreement between theory and experiment is the best