  We study the Ruderman-Kittle-Kasuya-Yosida (RKKY) interaction in the presence
of spin polarized two dimensional Dirac fermions. We show that a spin
polarization along the z-axis mediates an anisotropic interaction which
corresponds to a XXZ model interaction between two magnetic moments. For
undoped graphene, while the $x$ part of interaction keeps its constant
ferromagnetic sign, its $z$ part oscillates with the distance of magnetic
impurities, $R$. A finite doping causes that both parts of the interaction
oscillate with $R$. We explore a beating pattern of oscillations of the RKKY
interaction along armchair and zigzag lattice directions, which occurs for some
certain values of the chemical potential. The two characteristic periods of the
beating are determined by inverse of the difference and the sum of the chemical
potential and the spin polarization.
