  Several experiments have recently found room-temperature ferromagnetism in
graphite-like carbon based materials. This paper offers a model explaining such
ferromagnetism by using an asymmetric nano-graphene. Our first typical model is
C48H24 graphene molecule, which has three dihydrogenated (-CH2) zigzag edges.
There are several multiple spin states competing for stable minimum energy in
the same atomic topology. Both molecular orbital and density function theory
methods indicate that the quartet state(S=3/2) is more stable than that of
doublet (S=1/2), which means that larger saturation magnetization will be
achieved. We also enhanced this molecule to an infinite length ribbon having
many (-CH2) edges. Similar results were obtained where the highest spin state
was more stable than lower spin state. In contrast, a nitrogen substituted
(-NH) molecule C45N3H21 demonstrated opposite results. that is, the lowest spin
state(S=1/2) is more stable than that of highest one(S=3/2), which arises from
the slight change in atom position.
