自旋为1/2的X-Y模型亚铁磁棱型链的热力学性质  

THERMODYNAMIC PROPERTIES OF SPIN-1/2 XY MODEL IN THE FERRIMAGNETIC DIAMOND CHAINS

作　　者：成泰民[1,2] 孙树生[1] 贾维烨[1] 葛崇员[1] 

机构地区：[1]沈阳化工大学数理系,沈阳110142 [2]吉林大学超硬材料国家重点实验室,长春130012

出　　处：《低温物理学报》2012年第6期417-424,共8页Low Temperature Physical Letters

基　　金：国家自然科学基金(批准号:10647138);中国博士后科学基金(批准号:200904501018);国家重点基础研究发展973计划项目(批准号:2011CB606404)资助的课题~~

摘　　要：本文利用不变本征算符法计算了低温下自旋为1/2的XY模型一维亚铁磁棱型链系统的元激发谱,并讨论了在此系统中不同的特殊情形下的元激发能量,从而给出体系的三个临界磁场强度的解析解HC1,HC2,Hpeak.体系的比热随温度的变化出现了双峰现象.熵随外磁场的变化也出现了双峰现象,并且其双峰位置与临界磁场(HC1,HC2)相对应.这说明双峰源于体系的不同形式的能量之间的竞争.但是,在低温下比热随外磁场变化曲线在上述两个临界磁场处,比热出现极小值.在高温下体系的约化熵接近3ln2,在低温区hω3,k对体系熵的贡献大于hω1,k和hω2,k的贡献,并且在低温区hω1,k和hω2,k对体系熵的贡献几乎为零.在本文中详细讨论了上述现象的起因.The elementary excitation spectra of the one-dimensional spin-l/2 XY model in the ferrimagnetic diamond chain at low temperature were calculated by using lEO method in this paper. And the elementary excitations energy was discussed under different situations. Therefore, the analytic solutions of the three critical magnetic field intensity Hc~, Hc2, H~ were given In this system, the temperature dependent specific heat curves and the external magnetic field dependent entropy curves both showed the double peak structure, and the peak position corresponded to Hc~ and Hc~, respectively. This suggested that the double peak structure originated from the competition among the different types of energies. But the specific heat relative minimum values appeared at the position of hω1,k and hω2 on the external magnetic field dependent specific heat curves at low temperature. The reduced entropy of the system approached 31n2 at high temperature. In the low temperature region, the contribution of hω1,k and hω2 to the systemic entropy was bigger than the contribution of hω1,k and hω2 In addition, the contribution of hω1,k and hω2 to the systemic entropy was almost equal to zero. The origin of the above phenomenon was discussed in detail.

关 键 词：自旋为1 2的一维亚铁磁棱型链系统 比热 熵 不变本征算符法 

分 类 号：O482.5[理学—固体物理]