Tunable ferromagnetism in assembled two dimensional triangular graphene nanoflakes.

Triangular graphene nanoflakes (TGFs), due to their novel magnetic configurations, can serve as building blocks to design new magnetic materials. Based on spin polarized density functional theory, we show that the two dimensional (2D) structures composed of zigzag-edged TGFs linked by 1,3,5-benzenetriyl units (TGF(N)-C(6)H(3)) are ferromagnetic. Their magnetic moments can be tuned by changing the size and edge termination of TGFs, namely magnetic moments increase linearly with the size of TGFs, and double hydrogenation of the edge carbon atoms can significantly enhance stability of the ferromagnetic states. The dynamic stability of the assembled 2D structures is further confirmed by frequency calculations. The characteristic breathing mode is identified where the frequency changes with the inverse square root of the TGFs width, which can be used to identify the size of TGF(N)-C(6)H(3) in Raman experiments. This study provides new pathways to assemble 2D ferromagnetic carbon materials.