EPR study of nano-structured graphite

(Dated: August 23, 2011)We report on a systematic temperature dependent X-band electron paramagnetic resonance(EPR) study of nano-sized graphite particles prepared by ball-milling. In as-prepared samples avery intense and sharp EPR resonance at g= 2.0035 has been measured. The EPR linewidth showsa Korringa-like linear temperature dependence arising due to the coexistence and strong exchangecoupling of itinerant and localized edge states. With a prolonged aging in inert atmosphere changesin the EPR signal suggest gradual structural reconstruction where the localized edge-states dominatethe EPR signal. In this case the EPR spin susceptibility shows a maximum at ≈23K indicating thedevelopment of antiferromagnetic correlations as expected for the graphene lattice with a bipartitesymmetry.