The role of size in spin properties of zigzag graphene nanoribbon J.H. Zhao, X.Q. Dai, B. Zhao, Y.W. Dai and X. Zhao Eur. Phys. J. B, 85 6 (2012) 220 Published online: 25 June 2012 DOI: 10.1140/epjb/e2012-30077-3