广义布洛赫条件下二维晶格的磁交换作用

Magnetic exchange interaction in two-dimensional lattice under generalized Bloch condition

二维磁性材料是近几年新兴的研究领域,该材料在开发自旋电子器件等领域具备良好的应用潜能.为了了解二维磁性材料的磁性质,明确体系内各近邻磁性原子间的磁相互作用非常重要.第一性原理为各近邻磁交换参数的计算奠定了基础.目前各近邻参数的第一性原理计算常用的是能量映射法,但这种方法存在一定的缺陷.本文通过广义布洛赫条件推导了3种常见二维磁性结构的海森伯作用与Dzyaloshinskii-Moriya(DM)相互作用的自旋螺旋色散关系,这3种结构为四方结构,元胞包含一个磁性原子的六角结构,元胞包含两个磁性原子的六角结构.为了将本文推导的自旋螺旋色散关系应用于实际,我们通过第一性原理计算了一些材料的海森伯和DM作用的交换参数,这些材料分别是MnB,VSe_(2),MnSTe,Cr_(2)I_(3)C_(l3).其中,MnSTe和Cr_(2)I_(3)C_(l3)都属于二维Janus材料,磁性原子层的上下层对称性破缺,整个体系存在DM相互作用.

Two-dimensional magnetic material which has been rapidly developed in recent years,has potential applications in developing spintronic devices.In order to understand the magnetic properties of two-dimensional magnetic materials,it is necessary to comprehend the magnetic interaction which is estimated by the exchange parameters between the magnetic atoms.The calculation of the magnetic exchange parameters is based on the first-principle.The commonly used method of determining the values of exchange parameters is energy-mapping.However,this method has some disadvantages.In this paper,the spin-spiral dispersion relationship is derived under the Heisenberg interaction and the Dzyaloshinskii-Moriya(DM)interaction through the generalized Bloch condition of three common two-dimensional magnetic structures:a tetragonal structure,a hexagonal structure in which the cell contains one magnetic atom,a hexagonal structure in which the cell contains two magnetic atoms.The magnetic exchange parameters of some materials are calculated through the first principle.These materials are MnB,VSe_(2) MnSTe and Cr_(2)I_(3)C_(l3).Among them,the MnSTe and Cr_(2)I_(3)C_(l3) are two-dimensional Janus materials,which means that they have space-reversal symmetry broken,that is why there is DM interaction in the system.