过渡金属原子修饰二维有机网格结构磁晶各向异性能的研究
发布时间：2018-08-06 16:03
【摘要】：随着半导体科技的进步,个人电脑和智能终端产品的普及,人们对于信息存储的需求日益增大,因此关于超高存储密度的磁性存储材料出现了飞速的进步。为了提高磁性存储器件的存储密度,必须减小每一个磁性记录单元的尺寸大小,而尺寸减小所带来的过小的磁晶各向异性能(MAE)往往无法克服室温的热扰动,导致存储器件在使用过程中丢失信息数据。为了克服超顺磁现象的影响,高磁晶各向异性能的材料被提上了研究方案,但是过高的磁晶各向异性能会带来高的矫顽力,导致信息数据在写入存储器的过程变得非常困难。因此寻找具有合适磁晶各向异性能的磁性材料是当前磁性存储器发展的关键,并且如果能够对记录单元的磁晶各向异性能进行切实有效的调控,将会大大减低磁性记录材料的寻找难度,提高材料的利用价值。近年来,为了寻找具有合适磁晶各向异性能的磁性存储材料,人们在实验和理论上都进行了许多探索。研究发现,由于低维结构本身的各向异性,将过渡金属原子与低维体系结合往往可以带来较高的磁晶各向异性能。在本文中,我们利用基于密度泛函理论的缀加平面波方法软件包,通过多种过渡金属原子来修饰二维酞菁片层结构,研究体系的磁学性质。我们发现5d金属由于较高的自旋轨道耦合系数(SOC),使得修饰后的5d-Pc网格表现出较高的各向异性。且体系的磁晶各向异性能对金属原子d轨道的能级排布密切相关。以此为基础,我们通过引入O原子对金属原子的d轨道进行重排,提出了全新的轨道调控的方法,期望能够对新型磁性存储材料的设计提供一定的指导作用。我们的计算结构表明,当O原子吸附在金属原子上方,形成的O-MPc结构的金属原子轨道发生重排,而通过电场控制O原子的高度可以对d电子的能级进行精准的调控,从而可以直接控制体系的磁晶各向异性能。通过对比,发现这种调控方式更为直接有效,且调控范围远远高于传统调控手段。我们进一步通过卤素原子替代O原子进行了调控,证明了控制非金属原子与金属原子之间的相互作用大小就可以精准的控制能级排布,实现对磁晶各向异性能的有效调控。我们利用已有的研究手段和新型的调控方法探索了新型的金属有机框架结构(MOF),虽然这种新型的材料并没有表达出令人满意的磁学性质,但充分证明了d电子的轨道调控可以实现对体系磁晶各向异性能的大幅度控制。
[Abstract]:With the development of semiconductor technology and the popularity of personal computers and intelligent terminal products, the demand for information storage is increasing. Therefore, magnetic storage materials with ultra-high storage density have made rapid progress. In order to improve the storage density of magnetic memory devices, the size of each magnetic recording unit must be reduced, and the small magnetocrystalline anisotropy energy (MAE) can not overcome the thermal disturbance at room temperature. Causes the memory device to lose information data during use. In order to overcome the influence of superparamagnetism, the materials with high magnetocrystalline anisotropy energy have been proposed. However, the high magnetocrystalline anisotropy energy will lead to high coercivity, which makes it very difficult for information data to be written to the memory. Therefore, finding magnetic materials with appropriate magnetocrystalline anisotropy energy is the key to the development of magnetic memory, and if the magnetocrystalline anisotropy energy of the recording unit can be effectively regulated, It will greatly reduce the difficulty of finding magnetic recording materials and improve the utilization value of the materials. In recent years, in order to find magnetic storage materials with suitable magnetocrystalline anisotropic energy, many experiments and theories have been carried out. It is found that due to the anisotropy of the low-dimensional structure, the combination of transition metal atoms with low-dimensional systems often leads to higher magnetocrystalline anisotropy energy. In this paper, we study the magnetic properties of the system by modifying the two-dimensional phthalocyanine lamellar structure with a variety of transition metal atoms by using the density functional theory (DFT) based affixed plane wave method software package. We find that the modified 5d-Pc meshes exhibit high anisotropy due to the high spin-orbit coupling coefficient (SOC),) of 5d metals. The magnetocrystalline anisotropy energy of the system is closely related to the arrangement of the energy levels of the d orbitals of the metal atoms. On this basis, by introducing O atoms to rearrange the d orbitals of metal atoms, a new orbital control method is proposed, which is expected to provide some guidance for the design of new magnetic storage materials. Our computational structure shows that when O atoms are adsorbed on metal atoms, the metal atom orbitals of the O-MPc structure are rearranged, and the energy levels of d electrons can be precisely regulated by controlling the height of O atoms by an electric field. Thus the magnetocrystalline anisotropy energy of the system can be directly controlled. Through comparison, it is found that this regulation method is more direct and effective, and the range of regulation is much higher than that of traditional control means. We further control the energy levels by replacing O atoms with halogen atoms. It is proved that by controlling the interaction between nonmetallic atoms and metal atoms, we can precisely control the distribution of energy levels and realize the effective regulation of magnetocrystalline anisotropic energy. We have explored a new metal-organic frame structure, (MOF), using existing research tools and new regulatory methods, although this new material has not shown satisfactory magnetic properties. However, it is fully proved that the orbital control of d electrons can control the anisotropic energy of magnetocrystalline system greatly.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP333;O482.5
本文编号：2168239
[Abstract]:With the development of semiconductor technology and the popularity of personal computers and intelligent terminal products, the demand for information storage is increasing. Therefore, magnetic storage materials with ultra-high storage density have made rapid progress. In order to improve the storage density of magnetic memory devices, the size of each magnetic recording unit must be reduced, and the small magnetocrystalline anisotropy energy (MAE) can not overcome the thermal disturbance at room temperature. Causes the memory device to lose information data during use. In order to overcome the influence of superparamagnetism, the materials with high magnetocrystalline anisotropy energy have been proposed. However, the high magnetocrystalline anisotropy energy will lead to high coercivity, which makes it very difficult for information data to be written to the memory. Therefore, finding magnetic materials with appropriate magnetocrystalline anisotropy energy is the key to the development of magnetic memory, and if the magnetocrystalline anisotropy energy of the recording unit can be effectively regulated, It will greatly reduce the difficulty of finding magnetic recording materials and improve the utilization value of the materials. In recent years, in order to find magnetic storage materials with suitable magnetocrystalline anisotropic energy, many experiments and theories have been carried out. It is found that due to the anisotropy of the low-dimensional structure, the combination of transition metal atoms with low-dimensional systems often leads to higher magnetocrystalline anisotropy energy. In this paper, we study the magnetic properties of the system by modifying the two-dimensional phthalocyanine lamellar structure with a variety of transition metal atoms by using the density functional theory (DFT) based affixed plane wave method software package. We find that the modified 5d-Pc meshes exhibit high anisotropy due to the high spin-orbit coupling coefficient (SOC),) of 5d metals. The magnetocrystalline anisotropy energy of the system is closely related to the arrangement of the energy levels of the d orbitals of the metal atoms. On this basis, by introducing O atoms to rearrange the d orbitals of metal atoms, a new orbital control method is proposed, which is expected to provide some guidance for the design of new magnetic storage materials. Our computational structure shows that when O atoms are adsorbed on metal atoms, the metal atom orbitals of the O-MPc structure are rearranged, and the energy levels of d electrons can be precisely regulated by controlling the height of O atoms by an electric field. Thus the magnetocrystalline anisotropy energy of the system can be directly controlled. Through comparison, it is found that this regulation method is more direct and effective, and the range of regulation is much higher than that of traditional control means. We further control the energy levels by replacing O atoms with halogen atoms. It is proved that by controlling the interaction between nonmetallic atoms and metal atoms, we can precisely control the distribution of energy levels and realize the effective regulation of magnetocrystalline anisotropic energy. We have explored a new metal-organic frame structure, (MOF), using existing research tools and new regulatory methods, although this new material has not shown satisfactory magnetic properties. However, it is fully proved that the orbital control of d electrons can control the anisotropic energy of magnetocrystalline system greatly.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP333;O482.5
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