In this paper, the magnetic properties of ferromagnetic graphene nanostructures, especially the dependence of the magnetism on finite temperature, are investigated by use of the many-body Green’s function method of quantum statistical theory. The spontaneous magnetization increases with spin quantum number, and decreases with temperature. Curie temperature increases with exchange parameter J or the strength K2 of single-ion anisotropy and spin quantum number. The Curie temperature TC is directly proportional to the exchange parameter J. The spin-wave energy drops with temperature rising, and becomes zero as temperature reaches Curie temperature. As J(p,q)=0, ω1=ω2, the spin wave energy is degenerate, and the corresponding vector k=(p, q) is called the Dirac point. This study contributes to theoretical analysis for pristine two-dimensional magnetic nanomaterials that may occur in advanced experiments.
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