Finite-Temperature Properties of Three-Dimensional Chiral Helimagnets
Finite-Temperature Properties of Three-Dimensional Chiral Helimagnets
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DOI：
10.7566/jpsj.85.074710
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发表时间：
2016-07-15
影响因子：
1.7
通讯作者：
Kato, Yusuke
中科院分区：
文献类型：
--
作者：
Shinozaki, Misako;Hoshino, Shintaro;Kato, Yusuke
我们通过分析自旋哈密顿量来研究有限温度下的三维 (3d) 经典手性螺旋磁体，自旋哈密顿量是在简单立方晶格上定义的，由海森堡交换、单轴 Dzyaloshinskii-Moriya 相互作用以及由于在垂直于螺旋轴的平面上施加的磁场而产生的塞曼能量组成。我们考虑到已知单轴手性螺旋磁体 CrNb3S6 的准二维性，并采用三种方法：（i）传统平均场（MF）分析，我们称之为 3dMF 方法，（ii）称为 2dMC-1dMF 方法的混合方法，该方法由经典蒙特卡罗（MC）模拟和分别应用于层内和层间相互作用的 MF 近似组成，以及（iii）简单 MC 模拟(3dMC) 零场。通过 3dMF 方法计算的磁化强度的温度依赖性显示出与实验中观察到的类似尖点结构。在没有磁场的情况下，2dMC-1dMF 和 3dMC 都会产生相似的转变温度值。 2dMC-1dMF 方法以可访问的数值成本提供热力学性质的定量描述，即使在外部场下也是如此。
We study a three-dimensional (3d) classical chiral helimagnet at finite temperatures through analysis of a spin Hamiltonian, which is defined on a simple cubic lattice and consists of the Heisenberg exchange, monoaxial Dzyaloshinskii-Moriya interactions, and the Zeeman energy due to a magnetic field applied in the plane perpendicular to the helical axis. We take account of the quasi-two-dimensionality of the known monoaxial chiral helimagnet CrNb3S6 and we adopt three methods: (i) a conventional mean-field (MF) analysis, which we call the 3dMF method, (ii) a hybrid method called the 2dMC-1dMF method, which is composed of a classical Monte Carlo (MC) simulation and a MF approximation applied respectively to the intra-and interlayer interactions, and (iii) a simple-MC simulation (3dMC) at zero field. The temperature dependence of the magnetization calculated by the 3dMF method shows a cusp-like structure similar to that observed in experiments. In the absence of a magnetic field, both 2dMC-1dMF and 3dMC yield similar values of the transition temperature. The 2dMC-1dMF method provides a quantitative description of the thermodynamic properties, even under an external field, at an accessible numerical cost.