采用相关有效场理论,对具有正方点阵结构的S=2横向Ising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的磁化曲线.研究发现在基态下,系统随晶场或横场的变化产生了一级有序—有序相变、—级有序—无序相变及二级相变,二级相变普遍存在,一级相变只存在于狭窄的晶场和横场范围内.%Using the correlated effective-field theory, the spin-2 transverse Ising model with the crystal field for the square lattice has been investigated. The expressions of magnetization were obtained and by numerical calculation the ground-state magnetization curves were given. It was found that there were the first order-order phase transitions, the first order-disorder phase transitions and the second order phase transitions in the ground state. The second order transitions are widespread, and the first order transitions are occurred in the very narrow range of crystal field and transverse field.
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