Effect of optical phonon–magnon interaction on the magnon damping at finite temperature

A magnon–phonon interaction model is set up in a two-dimensional ferromagnetic compound square-lattice system. By using Matsubara Green function theory we have calculated the magnon damping on the main symmetric lines in the Brillouin zone, compared the influences of magnetic ion optical-mode phonon and non-magnetic ion optical-mode phonon on the magnon damping of the system, and discussed the influences of the parameter variations and temperature on the magnon damping. The results show that the coupling of the optical-mode phonon and the magnon plays an important role for the magnon damping, especially the longitudinal optical-mode phonon contributes the most for the magnon damping. It is also found that the effect of the non-magnetic ion’s optical-mode phonon on magnon damping is more significant than that of the magnetic ion. By the expression −ImΣ∗(1)(k)=ħ/(2τ), the magnon life-time and the magnon line-width are discussed either.