Irradiation-induced magnetism in graphite: a density functional study |
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Authors: | Lehtinen P O Foster A S Ma Yuchen Krasheninnikov A V Nieminen R M |
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Institution: | Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 Finland. |
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Abstract: | Recent experiments indicate that proton irradiation triggers ferromagnetism in originally nonmagnetic graphite samples while He ion bombardment has a much smaller effect. To understand the origin of irradiation-induced magnetism, we have performed spin-polarized density functional theory calculations of the magnetic properties of the defects which are most likely to appear under irradiation vacancies and vacancy-hydrogen complexes. Both defects are magnetic, but as for the latter we find that H adsorption on one of the vacancy dangling bonds gives rise to a magnetic moment double that of the naked vacancy. We show that for small irradiation doses vacancy-hydrogen complexes result in a macroscopic magnetic signal which agrees well with the experimental values. |
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