Magnetic And Electronic Properties Of X/Graphene(X=H,Fe,Co) Systems

Nanomagnetic storage materials have attracted considerable interests because of its great potential application in ultra-high-density data storage. It is thus important to search for a substrate materail which is desirable to accommodate naonomagetic record untis. Recently, it is found that graphene possesses robust two-dimensional crystal structure which comprises of a single layer of carbon atoms. Graphene would be a good candidate as an excellent substrate for magnetic clusters, nanowires and nanofilms. In this thesis, we investigate the magnetic and electronic properties of X /Graphene(X=H, Fe, Co) based on first-principle calculations.We study the structural distortion, formation energy, magnetic and electric properties of H chemisorption on graphene through DFT calculations by using the VASP package, which base on plane-wave pseudo-potential technique. It was strange that H/Graphene is spin polarized with magnetic moement 1μB. The spin density distribution analysis reveals that the C atom on each nearest grid was antiferromagnetically coupled. Interestingly, we found that there is a considerable gap for supercells (size of n×n) with n≠3m while the gap is much smaller for supercells with n=3m. The linear energy-momentum dispersion relation which is unique for single graphene sheet can not be found in those systems with n≠3m.Several chemisorption structures, including monomer, atomic chains, and monolayer of Fe and Co on graphene, are investigated within the frame of density of function. The magnetic and electronic properties of Fe(Co)/Graphene are calculated. For an isolated Fe or Co atom adsorbed on graphene, the magnetic moments are 2.00μB and 1.04μB, respectively. For Fe or Co atomic chains grown on graphene, the magnetic moments for linear chains are 3.11μB,1.66μB, while 2.78μB,1.88μB in zigzag chains, respectively. We also calculated the magnetic moment and magnetic anisotropy energy of Fe-5d(Ta-Pt) biatomic chains. It is found that Fe-Ta, Fe-W, Fe-Re and Fe-Os biatomic chains can maintain rather large spin magnetic moments on graphene.