亚铁磁系统的补偿温度研究

The investigation of the compensation temperature of ferrimagnetic systems

基于格林函数方法,通过对交换项和单离子各向异性项分别采用Tyablikov退耦近似和Callen退耦近似,我们探究了三维亚铁磁系统补偿温度出现的条件.结果表明:大自旋子晶格的磁化强度-m_b和小自旋子晶格磁化强度m_a都随温度升高而下降,但两者速度不同.前者快于后者才能出现补偿温度,而小自旋的次近邻相互作用J_(aa)和/或单离子各向异性D_a可促进这一点实现.对于各种情况研究得到的结论是:对于所研究的模型,系统出现补偿温度的必要条件是D_a或J_(aa)至少有一个不为零,并且其值要大于某个特定的值.这个特定的值的大小依赖于系统其他参量的取值.

Based on the Green＇s function method, by using the Tyablikov and Callen approximation to decouple the exchange interactions and single-ion anisotropy, respectively, we study the condition of the compensation temperature appearance of the three-dimensional ferrimagnetic system. Our results show that both -mb in the large spin sublattice and ma in the small spin sublattice decrease with increasing temperature, but their speed are different. When the former larger than latter, the compensation temperature can appear. Our investigation show that the next-nearest neighbor exchange Jag and/or single-ion anisotropy Da of small spin can help our to achieve it. Therefore, our conclusion： for our ferrimagnetic system, the prerequisite of the compensation temperature appearance is that the system must at least have a nonzreo Jaa or single-ion anisotropy D. And its value should be beyond a certain value which depends on other parameters in Hamiltonian.