  We have investigated the variation in the magnetization of highly ordered
pyrolytic graphite (HOPG) after neutron irradiation, which introduces defects
in the bulk sample and consequently gives rise to a large magnetic signal. We
observe strong paramagnetism in HOPG, increasing with the neutron fluence. We
correlate the induced paramagnetism with structural defects by comparison with
density-functional theory calculations. In addition to the in-plane vacancies,
the trans-planar defects also contribute to the magnetization. The lack of any
magnetic order between the local moments is possibly due to the absence of
hydrogen/nitrogen chemisorption, or the magnetic order cannot be established at
all in the bulk form.
