随机横场与晶场作用混合自旋系统的热力学性质

利用有效场理论和切断近似，在伊辛模型的框架内考虑随机横场与晶场作用的混合自旋1/2 和自旋1系统的热力学性质。重点研究了晶场、横场和随机浓度对混合自旋系统相变的影响 ，研究发现在随机横场条件下，较小的晶场存在并不能改变临界横场阈值；取较大横场值时 在某些随机浓度的范围内出现重入相变现象，而取较小横场值时则没有出现重入相变现象。 给出了有关相图并进行了讨论。 关键词： 混合自旋系统 伊辛模型 热力学性质 随机横场

Thermodynamic properties of random transverse mixed Ising spin system with cryst al field

Making use of the effective field theory (EFT) and a cutting approximation, in the framework of Ising model, we investigate the thermodynamic properties of a random transverse mixed spin system with a crystal field. Special emphasis is placed on the influence of crystal field, transverse field and random concentration on phase transitions of the system. Our studies find that a smaller crystal field cannot change the percolation threshold of the critical transverse field in the presence of a random transverse field, and that the reentrant phenomena shall appear in the range of random concentration concerned when the transverse field takes a larger value, where as the reentrant phenomena do not occur and when the transverse field takes a smaller value. These new thermodynamic properties have not been reported in previous works so far as we know. We give a series of pha se diagrams and discuss them in detail.