In this paper, in order to explore high-spin carbon-based magnetic materials with strong ferromagnetic coupling, geometric structure, electronic structure and magnetic properUes of alternating stacks of n-radical-halogenated-hydrocarbons and diamagnetic molecules have been investigated based on density-functional theory with dispersion correction. These alternating stacks are predicted to avoid the typical antiferromagnetic spin-exchange of indentical face-to-face radicals via spin polarization of a diamagnetic molecule in between. the results show that n-radicalhalogenated-hydrocarbons like perchlorophmalenyl (Cl3 C19) is strong ferromagnetzc coupling if alternatingly stacked with aromatics like fluprinated coronene (C24F12) or coronene (C24H12), while fluorinated perinaphthenyl (C12F9) and permaphthenyl (C13H9) are not an equally good choice. The role of ligand configuration in determining exchange coupling in stacks is discussed. These results would give some hints for designing new high-spin carbon-based ferromqgnetic materials.