The ferromagnetic order in graphene
  The conditions for spontaneous magnetization in a single graphene sheet are discussed in the context of Mermin-Wagner theorem. It is rigorously proved that at any nonzero temperature the graphene monolayer is nonmagnetic as long as its intrinsic symmetry is preserved. Any electronic fluctuations breaking the pseudospin conservation law can be responsible for the existence of ferromagnetic order inside the graphene structure. 
L. Wojtczak
cond-mat.mes-hall