高自旋BC模型基态相变的研究

Research of Ground-state Phase Transitions of High-spin BC Model

采用相关有效场理论,对具有正方点阵结构的S=2横向BC模型,推导出系统的磁矩公式,并利用数值计算方法得到了基态相图。研究发现三种相变线将相图分成三个区域:有序铁磁相O1、有序铁磁相O2及无序顺磁相P,一级有序-有序相变线将铁磁相分成了O1及O2,并使铁磁相O2的区域非常狭窄。

investigated. Using the correlated effective-field theory, the spin-2 transverse BC model for the square lattice is The expressions of magnetization are obtained and by numerical calculation the ground-state phase di- agram is given. It is found that there are three areas divided by the three phase transition lines in the phase dia- gram： the order ferromagnetic phaseO1 , the order ferromagnetic phase O2 and the disorder paramagnetic phase P. The ferromagnetic phase is divided by the first order-order phase transition line into O1 and O2 , and the area of the ferromagnetic phase O2 is very narrow.