Electron spin resonance in presence of a magnetic impurity in graphene

The ESR of a magnetic probe sited at a distance R from an adatom in graphene, interacting via a RKKY interaction, is studied. The spin relaxation rate of the magnetic probe in the case of pristine graphene satisfies a T-3 dependence for all temperatures at the Dirac point. However, away from the Dirac point a T-3 dependence is observed only for high temperatures unlike the Korringa behavior at low temperatures. Moreover, the zero-temperature relaxation rate of the pristine graphene demonstrates a quadratic dependence on the chemical potential. In the presence of the magnetic adatom hybridized with one site of the graphene sublattice we observe a dip in the relaxation rate away from the Dirac point. At the Dirac point a deviation from the T-3 dependence is observed. The presence of the Coulomb interaction U also modifies the zero-temperature relaxation rate when compared to that of pristine graphene. The transition from the magnetic state to the non-magnetic state is also characterized by a minimum in the relaxation rate. (C) 2012 Elsevier Inc. All rights reserved.