一种等效于反铁磁海森伯混合自旋链的铁磁-反铁磁交替自旋链

利用严格对角化方法研究了一种自旋为1/2的铁磁-反铁磁交替自旋链的物理性质.计算了自旋关联函数、自旋z方向分量、自旋激发谱和磁化曲线等基本物理量,并将这些物理量和自旋为(1,1/2)的混合反铁磁自旋链对应的物理性质进行了比较.结果表明,当铁磁作用居于主导地位时,该模型的物理行为等效于混合自旋模型.因此,可以通过分析铁磁-反铁磁交替自旋链的物理性质研究混合自旋链的物理行为.

A kind of ferromagnetic-antiferromagnetic alternating spin chain equivalent to the mixed spin Heisenberg chain

By using the method of exact diagonalization,the properties of the spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain are investigated.The spin-spin correlation,the sublattice magnetizations,the spin excitation spectrum and the magnetization curve of the model are calculated and compared with the corresponding properties of the mixed spin chain.The results show that the behaviors of the alternating Heisenberg chain are equivalent to those of the mixed spin chain when the ratio of antiferromagnetic to ferromagnetic coupling strengthαis very small.So,the properties of the mixed spin chain can be analyzed by using the spin-1/2 ferromagnetic-antiferromagnetic-antiferromagnetic alternating Heisenberg chain.