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Magnetic properties of sulfur-doped graphene

Authors/others:Zhu, J. (Clemson University) Park, H. (Ohio State University) Podila, R. (Clemson University) Wadehra, A. (Ohio State University) Ayala, P.Oliveira, L. (Clemson University) He, J. (Clemson University) Zakhidov, A. A. (University of Texas, Dallas) Howard, A. (University of Texas, Dallas) Wilkins, J. (Ohio State University) Rao, A. M. (Clemson University)

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.

Number of pages:7
Date of publication:1.3.2016
Journal title:Journal of Magnetism and Magnetic Materials
Digital Object Identifier (DOI):https://doi.org/10.1016/j.jmmm.2015.10.012
Publication Type:Article
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