Magnetic Ordering in Porous Graphenes

Magnetic ordering in porous graphenes is analyzed by crystal orbital methods. While in triangle- and parallelogram-pored graphenes, the frontier bands have wide band widths, and in hexagon-pored graphenes, the HOCOs (highest occupied crystal orbitals) and LUCOs (lowest unoccupied crystal orbitals) are completely flat at the Huckel approximation. The flat bands in the resultant honeycomb systems are disjoint/nondisjoint composite types, and ferromagnetic interactions in the cationic and anionic states are predicted by quantum-chemical calculations including electronic correlations. Possible isoelectronic systems with nitrogen and boron atoms are also investigated as spin doped materials. The origin of spin alignment and pore size effects on magnetism are clarified by Wannier analysis. These systems are promising candidates for two-dimensional organic ferromagnets.