Two-Dimensional sp²Carbon Network of Fused Pentagons: All Carbon Ferromagnetic Sheet

Based on first-principles total-energy calculations, we investigate geometric and electronic structures of two-dimensional stable carbon allotropes comprised of pentagonal rings. We found that the sp2 carbon sheet has a slightly higher total energy than C60 and retains its planar structure up to 1000 K, indicating that the sheet is both energetically and kinetically stable. The electronic structure of the sheet is found to be a metal with a flat dispersion band at the Fermi level, leading to spin polarization on the sheet. The polarized electron spin is ferromagnetically aligned and extends throughout the sheet with a spin moment of 0.62 µB/nm2.