过渡族金属替代掺杂单层SnS磁性的第一性原理研究
发布时间：2019-03-12 20:43
【摘要】：由于具有独特的性质,原子厚度的二维磁性材料受到广泛的关注。二维半导体材料通常是内秉非磁性的,这限制了它们在自旋电子学上的应用,为使其有效地应用于自旋电子器件,有必要在这些非磁性材料中引入可调控的磁性。研究表明,施加应力、引入空位缺陷、替代掺杂和吸附等方法均能够在二维半导体材料中有效地引入磁性。目前,过渡族金属原子替代掺杂的方法已被广泛用于二维半导体的磁性调控。与Phosphorene类似,α相单层Sn S是非磁性半导体,带隙约为1.38 e V,因此α相单层Sn S有望作为稀磁半导体基底材料应用于自旋电子学。目前,没有关于在α相单层Sn S中引入磁性的相关报道。本论文采用基于密度泛函理论的第一性原理计算的方法,研究了过渡族金属元素替代Sn掺杂对单层Sn S的几何结构、电子结构和磁性的影响。主要研究内容和研究结果如下:1、对于V,Cr,Mn,Fe,Co和Ni替代Sn掺杂的单层Sn S,GGA的计算结果显示:Ni掺杂的单层Sn S不具有磁性,而一个替代掺杂的V,Cr,Mn,Fe和Co原子在单层Sn S中分别产生3μ,4μ,5μ,4μ和3μ的磁矩,磁矩主要由掺杂原子的3d轨道中未配对的电子所提供,掺杂原子周围近邻Sn和S原子的p轨道也有部分贡献。Ni掺杂单层Sn S没有磁性的原因是在费米能附近的能带具有较强的巡游性。进一步的计算表明两个掺杂的Cr原子之间存在长程的铁磁耦合。2、对于V,Cr,Mn,Fe,Co和Ni替代Sn掺杂的单层Sn S,GGA+U的计算结果显示:一个替代掺杂的V,Cr,Mn,Fe,Co和Ni原子在单层Sn S中分别产生了3μ, 4μ, 5μ, 4μ, 3μ和2μ的磁矩。与GGA的计算结果相比,掺杂原子d电子的关联效应明显地增加了V,Cr,Mn,Fe,Co替代掺杂单层Sn S自旋极化态的稳定性,特别是对Ni替代掺杂的单层Sn S,Ni原子d电子的关联效应使其基态由自旋非极化态变为自旋极化态。另外,3d电子的关联效应不仅明显地增加掺杂原子的磁矩贡献,而且显著地改变了两个掺杂原子之间的磁耦合。这些结果显示:关联效应对掺杂原子d轨道的影响是不可忽略的。
[Abstract]:Due to its unique properties, two-dimensional magnetic materials with atomic thickness have received extensive attention. Two-dimensional semiconductor materials are usually intrinsically nonmagnetic, which limits their application in spintronics. In order to effectively apply them to spintronic devices, it is necessary to introduce controllable magnetism into these non-magnetic materials. The results show that magnetic properties can be effectively introduced into two-dimensional semiconductor materials by applying stress, introducing vacancy defects and substituting doping and adsorption. At present, the substitution of transition metal atoms for doping has been widely used in the magnetic regulation of two-dimensional semiconductors. Similar to Phosphorene, 伪 phase monolayer Sn S is a nonmagnetic semiconductor with a band gap of about 1.38eV.Therefore, 伪 phase monolayer Sn S is expected to be used in spintronics as a diluted magnetic semiconductor substrate. At present, there are no reports about the introduction of magnetic properties into 伪-phase monolayer Sn S. In this paper, the influence of transition metal elements instead of Sn doping on the geometric structure, electronic structure and magnetic properties of monolayer Sn S is studied by using the first principle calculation method based on density functional theory (DFT). The main contents and results are as follows: 1. For V, Cr, mn, Fe, Co and Ni instead of Sn-doped monolayer Sn S, the calculation results show that the Ni-doped monolayer Sn S is not magnetic, but a substitute for V, Cr, mn, and so on. The Fe and Co atoms produce 3 渭, 4 渭, 5 渭, 4 渭 and 3 渭 magnetic moments in the monolayer Sn S, respectively. The magnetic moments are mainly provided by the unpaired electrons in the 3D orbitals of the doped atoms. The p-orbitals of the adjacent Sn and S atoms around the doped atoms also contribute partially. The reason that Ni-doped monolayer Sn S has no magnetism is due to the strong touring of the energy bands near the Fermi energy. Further calculation shows that there is a long-range ferromagnetic coupling between the two doped Cr atoms. 2. For V, Cr, mn, Fe, Co and Ni instead of Sn doped monolayer Sn S, the calculation results of GGA U show that a substitution of V, Cr, mn, Cr, mn is obtained. Fe,Co and Ni atoms produce magnetic moments of 3 渭, 4 渭, 5 渭, 4 渭, 3 渭 and 2 渭 in monolayer Sn S, respectively. Compared with the calculated results of GGA, the correlation effect of d electrons of doped atoms significantly increases the stability of spin polarization states of doped monolayer Sn S substituted by Co, Cr, mn, Fe, Co, especially for Ni instead of doped monolayer Sn S. The correlation effect of d-electrons in Ni atom makes the ground state change from spin-non-polarization state to spin-polarization state. In addition, the correlation effect of 3D electrons not only significantly increases the magnetic moment contribution of the doped atoms, but also significantly changes the magnetic coupling between the two doped atoms. These results show that the effect of correlation effect on the d-orbitals of doped atoms is not negligible.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O469
[Abstract]:Due to its unique properties, two-dimensional magnetic materials with atomic thickness have received extensive attention. Two-dimensional semiconductor materials are usually intrinsically nonmagnetic, which limits their application in spintronics. In order to effectively apply them to spintronic devices, it is necessary to introduce controllable magnetism into these non-magnetic materials. The results show that magnetic properties can be effectively introduced into two-dimensional semiconductor materials by applying stress, introducing vacancy defects and substituting doping and adsorption. At present, the substitution of transition metal atoms for doping has been widely used in the magnetic regulation of two-dimensional semiconductors. Similar to Phosphorene, 伪 phase monolayer Sn S is a nonmagnetic semiconductor with a band gap of about 1.38eV.Therefore, 伪 phase monolayer Sn S is expected to be used in spintronics as a diluted magnetic semiconductor substrate. At present, there are no reports about the introduction of magnetic properties into 伪-phase monolayer Sn S. In this paper, the influence of transition metal elements instead of Sn doping on the geometric structure, electronic structure and magnetic properties of monolayer Sn S is studied by using the first principle calculation method based on density functional theory (DFT). The main contents and results are as follows: 1. For V, Cr, mn, Fe, Co and Ni instead of Sn-doped monolayer Sn S, the calculation results show that the Ni-doped monolayer Sn S is not magnetic, but a substitute for V, Cr, mn, and so on. The Fe and Co atoms produce 3 渭, 4 渭, 5 渭, 4 渭 and 3 渭 magnetic moments in the monolayer Sn S, respectively. The magnetic moments are mainly provided by the unpaired electrons in the 3D orbitals of the doped atoms. The p-orbitals of the adjacent Sn and S atoms around the doped atoms also contribute partially. The reason that Ni-doped monolayer Sn S has no magnetism is due to the strong touring of the energy bands near the Fermi energy. Further calculation shows that there is a long-range ferromagnetic coupling between the two doped Cr atoms. 2. For V, Cr, mn, Fe, Co and Ni instead of Sn doped monolayer Sn S, the calculation results of GGA U show that a substitution of V, Cr, mn, Cr, mn is obtained. Fe,Co and Ni atoms produce magnetic moments of 3 渭, 4 渭, 5 渭, 4 渭, 3 渭 and 2 渭 in monolayer Sn S, respectively. Compared with the calculated results of GGA, the correlation effect of d electrons of doped atoms significantly increases the stability of spin polarization states of doped monolayer Sn S substituted by Co, Cr, mn, Fe, Co, especially for Ni instead of doped monolayer Sn S. The correlation effect of d-electrons in Ni atom makes the ground state change from spin-non-polarization state to spin-polarization state. In addition, the correlation effect of 3D electrons not only significantly increases the magnetic moment contribution of the doped atoms, but also significantly changes the magnetic coupling between the two doped atoms. These results show that the effect of correlation effect on the d-orbitals of doped atoms is not negligible.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O469
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