Void defect induced magnetism and structure change of carbon
  materials-1, Graphene nano ribbon
  Void defect is a possible origin of ferromagnetic like feature of pure carbon
material. Applying density functional theory to void defect induced graphene
nano ribbon (GNR), a detailed relationship between multiple spin state and
structure change was studied. An equitorial triangle of an initial initial void
having six electrons is distorted to isosceles triangle by rebonding carbon
atoms. Among possible spin states, the most stable state was Sz=2/2. The case
of Sz=4/2 is remarkable that initial flat ribbon turned to three dimentional
curled one having highly polarized spin configuration at ribbon edges. Total
energy of Sz=4/2 was very close to that of Sz=2/2, which suggests coexistence
of flat and curled ribbons. As a model of three dimensional graphite, bilayered
AB stacked GNR was analyzed. Spin distribution was limited to the void created
layer. Distributed void triangle show 60 degree clockwise rotation for
differrent site void, which was consistent with experimental observation using
the scanning tunneling microscope. (To be published on Journal of the Magnetic
Society of Japan, 2021 )
