Magnetic properties of sulfur-doped graphene

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:401

Article

Zhu, J.^1,3  Park, H.²  Podila, R.^1,3,4  Wadehra, A.²  Ayala, P.⁵  Oliveira, L.¹  He, J.¹  Zakhidov, A. A.⁶  Howard, A.⁶  Wilkins, J.²  Rao, A. M.^1,3,4 

[1] Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA

[2] Ohio State Univ, Dept Phys, Columbus, OH 43210 USA

[3] Clemson Univ, Clemson Nanomat Ctr, Clemson, SC 29634 USA

[4] Clemson Univ, COMSET, Clemson, SC 29634 USA

[5] Univ Vienna, Fac Phys, Vienna, Austria

[6] Univ Texas Dallas, Alan G MacDiarmid NanoTech Inst, Richardson, TX 75083 USA

关键词: Graphene;    Doping;    Ferromagnetic ordering;    Defects;    Density functional theory;    X-ray photoelectron spectroscopy;    Magnetization;   

DOI  :  10.1016/j.jmmm.2015.10.012

来源: Elsevier

【 摘 要 】

While studying magnetism of d- and f-electron systems has been consistently an active research area in physics, chemistry, and biology, there is an increasing interest in the novel magnetism of p-electron systems, especially in graphene and graphene-derived nanostructures. Bulk graphite is diamagnetic in nature, however, graphene is known to exhibit either a paramagnetic response or weak ferromagnetic ordering. Although many groups have attributed this magnetism in graphene to defects or unintentional magnetic impurities, there is a lack of compelling evidence to pinpoint its origin. To resolve this issue, we systematically studied the influence of entropically necessary intrinsic defects (e.g., vacancies, edges) and extrinsic dopants (e.g., S-dopants) on the magnetic properties of graphene. We found that the saturation magnetization of graphene decreased upon sulfur doping suggesting that S-dopants demagnetize vacancies and edges. Our density functional theory calculations provide evidence for: (i) intrinsic defect demagnetization by the formation of covalent bonds between S-dopant and edges/vacancies concurring with the experimental results, and (ii) a net magnetization from only zig-zag edges, suggesting that the possible contradictory results on graphene magnetism in the literature could stem from different defect-types. Interestingly, we observed peculiar local maxima in the temperature dependent magnetizations that suggest the coexistence of different magnetic phases within the same graphene samples. (C) 2015 Elsevier B.V. All rights reserved.

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