低温下二维绝缘铁磁体的磁振子寿命

在二维正方绝缘铁磁系统基础上建立了一个磁振子-声子相互作用模型. 利用格林函数方法研究了磁振子-声子相互作用下的二维绝缘铁磁体的磁振子衰减(即-ImΣ^*(1)(k)), 计算了布里渊区的主要对称点线上的-ImΣ^*(1)(k).发现在布里渊区边界区域磁振子衰减很明显, 但小波矢区(k_xa/π＜0.22附近)磁振子衰减非常弱, 而且温度很低时磁振子衰减有极大值. 比较了纵向声子与横向声子对磁振子衰减的影响, 也讨论了各项参数的变化对磁振子衰减的影响. 根据关系式-Im^*(1)(k)=/(2τ)可以对磁振子寿命进行判断. 关键词： 磁振子-声子相互作用 磁振子衰减 铁磁体 磁振子寿命

Magnon lifetime of two-dimensional insulating ferromagnet at low temperature

A magnon-phonon interaction model is built in two-dimensional insulating ferromagnet. By using Matsubara Green function theory, we have studied the magnon damping -ImΣ^*(1)(k), and calculated the magnon damping -ImΣ^*(1)(k) curve on the main symmetric point and line in the Brillouin zone for different parameters of the system. It is concluded that at the boundary of Brillouin zone there is a strong magnon damping. But the magnon damping is very small on zones of small wave vectors, and magnon damping has maximal value at very low temperature. The influences of longitudinal phonon and transverse phonon on the magnon damping are compared, and the influences of the parameters are also illustrated. According to expression -ImΣ^*(1)(k)=/(2τ), the magnon lifetime is discussed.