有限温度下二维Heisenberg铁磁系统的横向声频支声子激发  

Transverse acoustic phonon excitation of two-dimensional Heisenberg ferromagnetic system

作　　者：成泰民[1] 鲜于泽[2] 

机构地区：[1]沈阳化工学院数理系,沈阳110142 [2]东北大学理学院,沈阳110004

出　　处：《物理学报》2006年第9期4828-4836,共9页Acta Physica Sinica

基　　金：辽宁省教育厅高等学校科学研究项目(批准号:2005325)资助的课题.~~

摘　　要：在二维正方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Matsubara格林函数理论研究了系统的横向声频支声子激发,计算了布里渊区的主要对称点线上的横向声频支声子色散曲线,发现在第一布里渊区的Σ线上,小波矢区(Γ附近kxa<0.2)横向声频支声子有硬化现象,但是在软化区(0.25<kxa<0.7)有横向声频支声子有软化现象,在M附近(0.75<kxa)横向声频支声子有硬化现象.在Δ线上没有发生横向声频支声子有软化与硬化现象.在Z线上小波失区(X附近kxa<0.65)横向声频支声子有软化现象,但是在M附近横向声频支声子有硬化现象.并且又讨论了各项参数对横向声频支声子激发的影响,发现磁振子-声子耦合与自旋波劲度常数对横向声频支声子软化起很大的作用.A magnon-phonon interaction model is developed on the basis of two-dimensional square Heisenberg ferromagnetic system. The transverse acoustic phonon excitation is studied through Matsubara Green function theory, and the transverse acoustic phonon dispersion curve is calculated at the main symmetric point and on the symmetric line in the first Brillouin zone. It＇s found that on the line ∑ in first Brillouin zone, there is hardening for the transverse acoustic phonon in the smaller wave vector zone （point P near kxα 〈 0.2）, but there is softening for the transverse acoustic phonon in the softening zone （0.25 〈 kxα 〈 0.7）, there is hardening for the transverse acoustic phonon at point M near （0.75 〈 kxα）. On the line △, there is no phonon softening and hardening for transverse acoustic phonon. On the line Z, there is softening for transverse acoustic phonon in smaller wave vector zone （ point X near kxα 〈 0.65 ）, but there is hardening for the transverse acoustic phonon at the point M nearby. The influences of different parameters on the transverse acoustic phonon excitation are also illustrated. It＇ s found that the coupling of the magnon-phonon coupling and the spin wave stiffness are the main factors affecting the transverse acoustic phonon softening.

关 键 词：磁振子-声子相互作用 横向声频支声子软化 Matsubara格林函数理论 铁磁系统 

分 类 号：O482.5[理学—固体物理]