有限温度下光频支声子-磁振子相互作用对磁振子寿命的影响

Effect of optical phonon-magnon interaction on the magnon life-time at finite temperature

在二维复式正方Heisenberg铁磁系统的基础上建立了磁振子-声子相互作用模型.利用松原格林函数理论研究了系统的磁振子寿命,计算了布里渊区的主要对称点线上的磁振子衰减的变化曲线,比较了磁性离子的与非磁性离子的光频支声子对磁振子衰减的影响以及各项参数的变化和温度对磁振子衰减的影响.发现光频支声子-磁振子耦合对磁振子衰减起主要作用,尤其是纵向光频支声子对磁振子衰减起更大的作用,并且非磁性离子的光频支声子对磁振子衰减的作用比磁性离子的光频支声子对磁振子衰减的作用更显著.根据关系式-Im∑*(1)(k)=/(2τ)可以对磁振子寿命进行判断.

A magnon-phonon interaction model is set up in a two-dimensional ferromagnetic double square-lattice system. By using the Matsubara Green function theory we have studied the magnon life-time of the system, calculated the magnon damping curves on the main symmetric line 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 magnon plays the main role in 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 nonmagnetic ion on magnon damping is more significant than that of the magnetic ion. According to the expression -Im∑＊（1）（k）=/（2τ）, the magnon life-time is discussed.