Muons and Hydrogen in Graphene

Macroscopic quantities of graphenes have been prepared by diff erent chemical methods and characterized by Muon Spin Rotation spectroscopy, which proved a useful tool to study the interactions of the hydrogen atom with the defective graphene plane. A clear muon spin precession is observed in all the samples, contrary to the standard behaviour of graphite. Its origin lies in the magnetic dipolar interactions of hydrogen nuclei present at defects and reveal the formation of an extremely stable CHMu (CH2) state. The signal amplitude suggests that vacancies saturated by hydrogen have an extraordinary hydrogen capture cross-section. In addition the Muon Spin Rotation results, together with our SQUID investigations, pose important limits on the debated possibility of magnetism in graphene: Muon Spin Rotation, indeed, is very sensitive to the local internal field and does not show the presence of any magnetization.