随机晶场作用的Blume-Capel模型的相图研究  

Phase diagrams of the random crystal field Blume-Cape model

作　　者：朱海霞[1] 晏世雷[2] 

机构地区：[1]盐城师范学院物理科学与电子技术学院,江苏盐城224002 [2]苏州大学物理科学与技术学院,江苏苏州215006

出　　处：《山东大学学报（理学版）》2011年第1期51-55,共5页Journal of Shandong University(Natural Science)

基　　金：江苏省高等学校自然科学重点基金资助项目(03KJA140117)

摘　　要：在有效场框架下,运用切断近似的方法,取自旋S为1的三维简立方格子,对随机晶场作用的Blume-Capel模型(BCM)相图进行研究,重点探讨随机晶场浓度和不同的晶场分布形式(晶场比率参数α)对相图的影响,具体分析了4种晶场分布形式:晶场稀疏分布,正负晶场对称分布,正负晶场非对称分布和负晶场随机分布,并给出相应的相图。在晶场稀疏情况下,三临界点(TCP)存在于一定的晶场浓度范围内,低温区域出现相变线的重入现象和晶场简并模式;α=-1.0和α=-0.4时,临界点存在的晶场浓度范扩大,相图出现正晶场分布,特别当α=0.4时,三临界点始终存在,重入现象和晶场简并模式消失,二级相变线始终与晶轴没有交点,相变线均无趋于∞,磁有序相范围减小。By using a cutting approximation, the phase diagrams of the spin 1 random crystal field Blume-Capel （BCM） model is investigated for a cubic lattice. We discuss in detail the influence of random crystal field concentration and crystal field ratio on the phase diagram. The effect of four kinds of the random crystal field on the phase diagrams is discussed： distribution of diluted crystal field, distribution of positive and negative symmetry crystal field, distribution of positive and negative non-symmetry crystal field and distribution of random negative crystal field, and phase diagrams are given. Under crystal field dilution condition, the tri-critical point （TCP） exists in a range of crystal field concentrations, and, phase diagrams show the reentrant phenomenon and crystal field degeneration pattern. Choosing crystal field ratio α = - 1.0 and α = - 0. 4, the range of crystal field concentration of existing TCP is extended. Phase diagrams show positive crystal field distribution. In particular, choosing α = 0. 4, TCP exists over all crystal field concentration, reentrant phenomenon and crystal field degeneration pattern disappear, and the phase transition lines have no meeting point with the crystal axis and D→∞. And, the range of magnetic order phase is reduced.

关 键 词：Blume—Capel模型 三临界点 相图 

分 类 号：O414.13[理学—理论物理]