Figure 3. Magnetic units and exchange interactions for the fluorine chains on the graphene basal plane.
(a) A zigzag chain of fluorine on graphene, with isocontour plots of the spin density obtained from the DFT calculations. Regions with opposite spin orientations are painted in red and blue. C and F atoms are represented by grey and yellow spheres, respectively. (b) The calculated spin density for a random network of both zigzag and armchair chains. (c) A model of a spin ladder of length Ns with an infinitely strong ferromagnetic intra-leg interaction JFM and an antiferromagnetic inter-leg coupling JAF. (d) A plot of the magnetic susceptibility χ(T,N)/C for the finite size spin ladder vs the reduced temperature T/JAF. The numbers near the curves correspond to Ns; the scaling constant is C = (g μB)2/3JAF, where g is the electron gyromagnetic ratio and μB is the Bohr magneton.