  Structural as well as magnetization studies have been carried out on graphite
samples irradiated by neutrons over 50 years in the CIRUS research reactor at
Trombay. Neutron diffraction studies reveal that the defects in irradiated
graphite samples are not well annealed and remain significant up to high
temperatures much greater than 653 K where the Wigner energy is completely
released. We infer that the remnant defects may be intralayer Frenkel defects,
which do not store large energy, unlike the interlayer Frenkel defects that
store the Wigner energy. Magnetization studies on the irradiated graphite show
ferromagnetic behavior even at 300 K and a large additional paramagnetic
contribution at 5 K. Ab-initio calculations based on the spin-polarized
density-functional theory show that the magnetism in defected graphite is
essentially confined on to a single 2-coordinated carbon atom that is located
around a vacancy in the hexagonal layer.
