横向随机晶场Ising模型的相图和磁化行为研究

在有效场理论和切断近似框架内，选择自旋S=1的二维方格子，研究横向随机晶场Ising模型的相图和磁化行为，重点是横向随机晶场浓度和晶场比率对相图和磁化的影响.给出了i>T-D_x空间的相图和m-T空间的磁化图.在晶场稀疏情况下，负晶场方向存在临界温度的峰值，正方向可出现重入现象.晶场比率取+0.5和-0.5时，磁有序相范围缩小，特别是晶场比率取-0.5时，随晶场浓度的降低，临界温度峰值从横向晶场负方向渡越到正方向.固定某一负晶场值，不同晶场比率的磁化行为有明显差异.同时与纵向稀疏晶场Ising模型结果进行有意义的比较. 关键词： 横向随机晶场Ising模型 相图 磁化行为

Phase diagrams and magnetization behaviors of transverse random crystal field Ising model

Within the framework of the effective field theory (EFT) and cutting approximation, the spin-1 transverse random crystal field Ising model is investigated for a square lattice. We discuss in detail the influence of transverse random crystal field concentration and crystal field ratio on the phase diagram and magnetization behavior. We give phase diagrams in T-D_x space and magnetization curves in m-T space. Under crystal field dilution condition, there exists the peak value of critical temperature in the direction of negative crystal field and reentrant phenomena in the direction of positive critical field. While choosing crystal field ratio α=+0.5 and α=-0.5, the range of magnetic ordered phase shrinks. In particular, we found, with decreasing of concentration, the peak value of critical temperature undergoes a crossover from negative to positive direction of transverse crystal field when the ratio α=-0.5. The magnetization behaviors have apparent difference for a given negative crystal field value when the crystal field ratio is different. We give a meaningful comparison with the results of Ising model with longitudinal dilution crystal field.