外场下金属原子掺杂硅烯体系磁性质的第一性原理研究

发布时间：2018-06-28 10:32

本文选题：硅烯 + 掺杂　；参考：《清华大学》2016年博士论文

【摘要】：硅烯是一种新型的二维纳米材料,无论是理论上还是实验上都已证实了稳定孤立单层硅烯的存在。鉴于硅烯纳米材料具有很高的应用价值,所以已有许多研究工作关于探究硅烯材料的各种性质,其中最为引人关注的一种性质为磁性。在本文的工作中,我们采用第一性原理计算方法研究金属原子替位掺杂硅烯体系的结构,电子性质和磁性质,以及在外电场或拉力作用下金属原子掺杂硅烯体系特殊的磁性变化。我们系统的研究了过渡金属原子(Sc-Zn)嵌入硅烯单空位体系的结构,电子性质和磁性质。研究发现,除Zn原子外其它9种金属原子(Sc-Cu)掺杂硅烯体系都会呈现两种稳定的结构,不同金属原子掺杂硅烯的结构会有不同的对称性,即使同种金属原子掺杂硅烯所产生的两种结构也可能具有不同的对称性。且计算发现有些金属原子掺杂硅烯体系所具有的磁矩大小会不同于其掺杂石墨烯的磁矩。我们对过渡金属原子替位掺杂硅烯体系施加外电场研究其电子性质和磁性质的变化。对于高浓度Fe原子掺杂硅烯体系,在外电场的作用下会呈现独特的开关效应。对于低浓度的Fe或Cr原子掺杂硅烯体系,在外界电场的作用下同一种金属原子掺杂硅烯的两种构型呈现完全不同的磁性变化,特别是Fe原子掺杂硅烯体系其中一种结构的磁性随外电场的变化可以类似的看作“磁电二极管”。无论是高浓度还是低浓度Fe和Cr原子掺杂硅烯体系,随着外电场的变化都会有一段近线性变化区域。外界拉力也可以影响硅基纳米材料磁性质。对Cr和Fe原子替位掺杂硅烯体系施加各向同性双轴拉力和单轴拉力,可以观察到掺杂体系显著的磁矩变化。当各向同性双轴拉力达到某一个小的临界值时,Cr和Fe原子掺杂硅烯体系会有一个快速地由低自旋态到高自旋态(4μB)的转变。在一定的单轴拉力作用下,Fe原子掺杂硅烯体系也会由一个几乎无磁态快速转变到一个较高的磁性状态(2μB),而Cr原子掺杂体系在外界单轴拉力作用下会逐渐增大到4μB左右的高自旋态。研究发现Fe和Cr原子掺杂硅烯体系磁矩的变化与外界拉力的大小和作用方式有密切的关系。
[Abstract]:Silyene is a new two-dimensional nano-material, which has confirmed the existence of stable monolayer silicon monolayers, both theoretically and experimentally. In view of the high application value of silicene nanomaterials, many researches have been done on exploring the various properties of silicene materials, among which the most attractive one is magnetism. In our work, we use first-principle method to study the structure, electronic and magnetic properties of substitution doped silicene system. And the special magnetic changes of metal atom doped silicene system under the action of external electric field or tensile force. The structure, electronic and magnetic properties of the transition metal atom (Sc-Zn) intercalated silicene single vacancy system have been systematically studied. It has been found that there are two stable structures in the system of nine metal atoms (Sc-Cu) except Zn atoms, and the structures of different metal atoms have different symmetries. Even the two structures produced by doping silicon with the same metal atom may have different symmetries. It is also found that the magnetic moment of some metal atoms doped with silicene is different from that of graphene. We applied an external electric field to the transition metal atom substituted doped silicene system to study the changes of its electronic and magnetic properties. For high concentration Fe doped silicene system, there is a unique switching effect under the action of external electric field. For low concentration Fe or Cr doped silicene system, the two configurations of the same metal atom doped with silicene show completely different magnetic changes under the action of external electric field. In particular, the magnetic properties of one of the structures of Fe doped silicene system can be regarded as magnetoelectric diodes similarly with the change of external electric field. Both high and low concentrations of Fe and Cr atoms doped in silicene system have a near linear range with the change of external electric field. The magnetic properties of silicon-based nanomaterials can also be affected by external tensile force. When isotropic biaxial tensile force and uniaxial tensile force are applied to the substitution doped silicene system with Cr and Fe atoms, significant magnetic moment changes can be observed in the doped system. When the isotropic biaxial tension reaches a small critical value, there will be a rapid transition from low spin state to high spin state (4 渭 B). Under the action of uniaxial tension, the Si-doped system of Fe atom also changes rapidly from an almost non-magnetic state to a relatively high magnetic state (2 渭 B), while the Cr atom doping system increases to 4 渭 B under the external uniaxial tension. The left and right high spin states. It is found that the variation of magnetic moment of Fe and Cr doped silicene system is closely related to the magnitude and mode of external tension.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O469

【相似文献】