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March 22, 2010

Removing Atoms from Graphite Can Create Local Magnetic Moments in Graphite

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The missing atom as a source of carbon magnetism. By removing individual atoms from a graphite surface, they can create local magnetic moments in the graphite.

Atomic vacancies have a strong impact in the mechanical, electronic and magnetic properties of graphene-like materials. By artificially generating isolated vacancies on a graphite surface and measuring their local density of states on the atomic scale, we have shown how single vacancies modify the electronic properties of this graphene-like system. Our scanning tunneling microscopy experiments, complemented by tight binding calculations, reveal the presence of a sharp electronic resonance at the Fermi energy around each single graphite vacancy, which can be associated with the formation of local magnetic moments and implies a dramatic reduction of the charge carriers' mobility. While vacancies in single layer graphene naturally lead to magnetic couplings of arbitrary sign, our results show the possibility of inducing a macroscopic ferrimagnetic state in multilayered graphene samples just by randomly removing single C atoms.

The full 8 page research paper is here on Arxiv



Our findings have strong implications both from an applied and a fundamental point of view. They provide a significant stimulus to the theoretical community demonstrating that for atomistically controlled experiments, tight-binding methods give an excellent description of graphene-like systems physics. The observed resonances indicate that vacancies should limit significantly the mobility of carriers in graphene, and enhance its chemical reactivity. The existence of sharp electronic resonances at the Fermi energy, strongly suggests the formation of magnetic moments around single vacancies in graphite surfaces, implying a magnetic phase for this free of impurities carbon system with high Curie temperatures and small magnetization moments, which indicates a suitable route to the creation of non-metallic, cheaper, lighter, and bio-compatible magnets

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