Rončík M, Balcerzak T, Szałowski K, Jaščur M
Department of Theoretical Physics and Astrophysics, Institute of Physics, P. J. Šafárik University in Košice, Park Angelinum 9, 040 01 Košice, Slovakia.
Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Łódź, ul. Pomorska 149/153, 90-236 Łódź, Poland.
J Phys Condens Matter. 2022 Oct 12;34(48). doi: 10.1088/1361-648X/ac976e.
A generalized spin-1/2 transverse field Ising model with a negative thermal expansion of the lattice is introduced and investigated using standard methods of statistical mechanics. Besides the volume-dependent magnetic energy, the static lattice energy, and anharmonic Einstein phonon energy are also considered in calculations. Analytic relations for the Gibbs free energy, magnetic moments, and equations of state are obtained, taking into account a simple volume dependence of all energy contributions. The ground-state and finite-temperature phase diagrams are discussed in detail for the strong and weak magneto-elastic coupling. It is clearly demonstrated that the generalized spin-1/2 transverse field Ising model exhibits a novel critical behavior, due to the strong negative expansion of the lattice, which is controlled by the strength of magneto-elastic coupling. The presented approach can be easily modified to study also other magnetic and non-magnetic crystalline models of solids.
引入了一种具有晶格负热膨胀的广义自旋 - 1/2 横向场伊辛模型，并使用统计力学的标准方法对其进行研究。在计算中，除了与体积相关的磁能外，还考虑了静态晶格能和非简谐爱因斯坦声子能量。考虑到所有能量贡献的简单体积依赖性，得到了吉布斯自由能、磁矩和状态方程的解析关系。详细讨论了强磁弹耦合和弱磁弹耦合情况下的基态和有限温度相图。结果清楚地表明，由于晶格的强负膨胀，广义自旋 - 1/2 横向场伊辛模型表现出一种新颖的临界行为，这种行为由磁弹耦合强度控制。所提出的方法可以很容易地修改，以研究固体的其他磁性和非磁性晶体模型。
