随机横场与晶场作用混合自旋系统的热力学性质

Thermodynamic properties of random transverse mixed Ising spin system with crystal field

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。

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 phase diagrams and,discuss them in detail.