Irradiation-induced magnetism in graphite: a density functional study.
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.
Lehtinen
P O
PO
Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 Finland.
Foster
A S
AS
Ma
Yuchen
Y
Krasheninnikov
A V
AV
Nieminen
R M
RM