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Magnetic structure at zigzag edges of bilayer ribbons

EDUARDO V. CASTRO1,* , N. M. R. PERES2, J. M. B. LOPES DOS SANTOS1

Affiliation

  1. CFP and Departamento de Física Faculdade Ciências, Universidade do Porto, P-4169-007 Porto, Portugal
  2. CFP and Departamento de Física Faculdade Ciências, Universidade do Minho, P-4710-057, Braga, Portugal

Abstract

We study the edge magnetization of bilayer graphene ribbons with zigzag edges. The presence of flat edge-state bands at the Fermi energy of undoped bilayer, which gives rise to a strong peak in the density of states, makes bilayer ribbons magnetic at the edges even for very small on-site electronic repulsion. Working with the Hubbard model in the Hartree Fock approximation we show that the magnetic structure in bilayer ribbons with zigzag edges is ferromagnetic along the edge, involving sites of the two layers, and antiferromagnetic between opposite edges. It is also shown that this magnetic structure is a consequence of the nature of the edge states present in bilayer ribbons with zigzag edges. Analogously to the monolayer case, edge site magnetization as large as m≈0.2 μB (per lattice site) even at small on-site Hubbard repulsion U≈0.3 eV is realized in nanometer wide ribbons..

Keywords

Bilayer ribbon, magnetic structure, Graphene.

Submitted at: April 1, 2008
Accepted at: July 1, 2008

Citation

EDUARDO V. CASTRO, N. M. R. PERES, J. M. B. LOPES DOS SANTOS, Magnetic structure at zigzag edges of bilayer ribbons, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 7, pp. 1716-1721 (2008)