Chamati Hassan, Romano Silvano
Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussée, 1784 Sofia, Bulgaria.
Physics Department, The University, via A. Bassi 6, 27100 Pavia, Italy.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Aug;90(2):022506. doi: 10.1103/PhysRevE.90.022506. Epub 2014 Aug 27.
At low temperatures, some lattice spin models with simple ferromagnetic or antiferromagnetic interactions (for example, nearest-neighbor interaction being isotropic in spin space on a bipartite three-dimensional lattice) produce orientationally ordered phases exhibiting nematic (second-rank) order, in addition to the primary first-rank one; on the other hand, in the literature, they have been rather seldom investigated in this respect. Here we study the thermodynamic properties of a three-dimensional model with dipolar-like interaction. Its ground state is found to exhibit full orientational order with respect to a suitably defined staggered magnetization (polarization), but no nematic second-rank order. Extensive Monte Carlo simulations, in conjunction with finite-size scaling analysis, have been used for characterizing its critical behavior; on the other hand, it has been found that nematic order does indeed set in at low temperatures, via a mechanism of order by disorder.
在低温下，一些具有简单铁磁或反铁磁相互作用的晶格自旋模型（例如，在二分三维晶格上自旋空间中最近邻相互作用是各向同性的）除了主要的一阶有序外，还会产生呈现向列（二阶）有序的取向有序相；另一方面，在文献中，它们在这方面很少被研究。在此我们研究具有类偶极相互作用的三维模型的热力学性质。发现其基态相对于适当定义的交错磁化（极化）呈现完全取向有序，但没有向列二阶有序。广泛的蒙特卡罗模拟结合有限尺寸标度分析已被用于表征其临界行为；另一方面，已发现向列有序确实在低温下通过无序诱导有序机制出现。
