  We employ large-scale quantum Monte Carlo simulations to study the magnetic
ordering transition among dilute magnetic moments randomly localized on the
graphene honeycomb lattice, induced by long-ranged RKKY interactions at low
charge carrier concentration. In this regime the effective exchange
interactions are ferromagnetic within each sublattice, and antiferromagnetic
between opposite sublattices, with an overall cubic decay of the interaction
strength with the separation between the moments. We verify explicitly, that
this commensurability leads to antiferromagnetic order among the magnetic
moments below a finite transition temperature in this two-dimensional system.
Furthermore, the ordering temperature shows a crossover in its power-law
scaling with the moments' dilution from a low- to a high-concentration regime.
