  We investigate the magnetism in graphite by controlled oxidation. Our
approach renders graphite an insulator while maintaining its structure. Fourier
transform infrared spectroscopy and X-ray absorption near edge structure
spectra reveal that graphite oxide has epoxy groups on its surface and it is
not thermally stable. Magnetic susceptibility data exhibit negative Curie
temperature, field irreversibility, and slow relaxation. The magnetic
properties diminish after the epoxy groups are destroyed. The overall results
indicate the unexpected magnetism is associated with the presence of epoxy
groups.
