Aging and annealing effects on the magnetic ordering induced by proton irradiation in graphite

Aging and annealing effects on the topography and the magnetic ordering induced by proton irradiation in highly oriented graphite samples have been studied with atomic force and magnetic force (MFM) microscopy. Clear changes in the magnetic and the topographic images after keeping the samples several months at room temperature and annealing at 1000 _C in vacuum are observed. These changes appear to be related to the diffusion of hydrogen in graphite. Clear differences are also observed in the magnetic images made with different magnetic probes by using MFM.