双层亚铁磁体超晶格的能谱

Energy spectra of double-layer ferrimagnetic superlattices

对双层亚铁磁超晶格的能谱进行理论研究.采用海森堡模型,利用线性自旋波近似、傅立叶变换和格林函数技术计算出色散关系和外磁场的临界值Bc.结果表明,系统的各个参数如:自旋量子数、层间交换耦合系数、层内交换耦合系数、各向异性参数、外磁场都对系统的磁性有着重要的影响.研究发现,当两个层的自旋量子数相等时,两个能谱简并,当两个层的自旋量子数不相等时,能谱分裂.一般情况下,两支能谱随着层间交换耦合系数、层内交换耦合系数和各项异性参数的增强而差值加大.外磁场的临界值Bc随各向异性参数D1和D2数值的增加而增强,随自旋量子数的增加而增加.层间交换耦合系数与层内交换耦合系数对外磁场的临界值Bc不产生影响.

Theoretical studies for the energy spectra of double-layer ferrimagnetic superlattice were carried out. The dispersion relation and critical yalue of external magnetic field Bc were calculated using Heisenberg model, linear spin wave approximation, Fourier transformation and Green＇s function technology. The result shows that the parameters of the system such as spin quantum number, interlayer exchange couplings, intralayer exchange couplings, anisotropy constant and external magnetic field have important effect on the magnetic properties. It has been found that when the spin quantum numbers of the double layers are same, two branches of energy spectra degenerate, and when the spin quantum numbers of the double layers are different, energy spectra split. Generally, the difference of two branches of energy spectra increase with increasing the interlayer exchange couplings, intralayer exchange couplings and anisotropy constant. The critical value of external magnetic field Bc increases with increasing the anisotropy constant D1 and D2 and spin quantum number. Interlayer exchange couplings and intralayer exchange couplings have no effect on the critical value of external magnetic field Bc.