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Magnetic and Electronic Properties of X/Graphene(X=H,Fe,Co) Systems

Author: LiShuHeng
Tutor: CaoJueXian
School: Xiangtan University
Course: Theoretical Physics
Keywords: Graphite sheet Magnetic Electronic Properties Density functional theory
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 51
Quote: 0
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Abstract


Nano-magnetic storage materials have potential applications of ultra-high density data storage, so by the people's attention. With the magnetic recording unit of the nano, how to find one suitable for accommodating a the nanometer magnetic recording unit of the base material and therefore become a very important problem faced by people. Recently, it was found that the graphite sheet has a two-dimensional crystal structure of monoatomic layer thickness. Therefore, it is expected, as the growth of magnetic clusters, nanowires, nano-film an excellent base to provide new ideas for the design of nano-magnetic storage materials. In this paper, first-principles calculation method based on the density functional theory, the magnetic and electronic properties of non-metallic elements H and transition metal elements such as Fe and Co adsorbed on graphite sheet. Its main contents include: the plane wave pseudopotential method, we use the VASP program package H / Graphene structural aberrations, the surface energy, magnetic and electronic properties. The calculation results show that the performance of the system ferromagnetic. Spin-charge density analysis showed that when the spontaneous magnetization in the system, each grid point and its nearest neighbor three grid of the local magnetic moments of antiferromagnetic coupling, alternating each grid point on the entire lattice spin direction. Very interesting system HIGraphene band structure changes with the adsorption of different concentrations exhibit different changes in behavior: When the supercell the size of the (n × n) n = 3m when the system band gap is very small, and peculiar to the graphite sheet. of pi and pi * with linear dispersion relation can be preserved; when n = 3m, the band gap of the system relative to the former is much larger, and pi and pi * linear dispersion relation of the band no longer exists. We consider the Fe (Co) / Graphene the system several possible adsorption structure, a detailed analysis of which FE, Co magnetic and adsorption mechanism. The results show that, Fe (CO) single atoms adsorbed on the surface of the graphite sheet when their magnetic moments were by 2.00μB and 1.04μB, and has a large adsorption capacity, and therefore capable of forming a stable adsorption structures; in a straight line when the Fe or Co zigzag atomic chains adsorbed on graphite sheet, the magnetic moment of Fe atoms 3.11μB and 2.78μB the magnetic moment of Co 1.66μB and 1.81μB. In addition, we also consider Fe and 5d transition metal elements (Ta-Pt) Fe-5d freedom of diatomic chain magnetic moments and magnetic anisotropy energy, and discuss the spin magnetic moment when they are adsorbed on graphite sheet changed. We found that the Fe-Ta, Fe-W, Fe-Re, Fe-Os diatomic chain adsorbed on the graphite sheet can be maintained large magnetic moment.

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