Orbital magnetization of graphene and graphene nanoribbons

We present a quantitative analysis on orbital magnetization of graphene under a magnetic field. The energy spectra were obtained by solving Harper equation for a honeycomb lattice. The effect of the next-nearest-neighbor hopping (NNNH) is to increase the period of the magnetic subbands in phi/phi(0) from 1 to 6 (where phi is the magnetic flux through a unit cell and phi(0) is the flux quanta). The shifts of the energy levels due to the NNNH vary with the magnetic field. The Holmholtz free energy at the points phi/phi(0)=6n+1 is lowered as compared to that with the nearest neighbor hopping only. For graphene nanoribbons, the magnetic susceptibility is very sensitive to the ribbon width and chirality. The zero-field susceptibility increase with the ribbon width. (C) 2008 American Institute of Physics.