Frequency Dependence of the Two-Magnon Ferrimagnetic Resonance Linewidth

The Sparks-Loudon-Kittel (SLK) two-magnon linewidth theory is modified in a way that takes into account a more reasonable model of the scattering center due to magnetic inhomogeneities. The inverse-square frequency dependence of the linewidth at high frequencies given by SLK is eliminated, and a weak frequency dependence similar, but not identical, to that found by the theories of Geschwind and Clogston and of Schlömann is obtained. Experimental data ranging over a factor of about ten in applied field divided by magnetization ($\propto$ frequency) gives excellent agreement with the modified SLK theory.