of these ones for spintronics applications, as opposed to using large flakes of graphene. Although our conclusions are based on the simplest case of two H atoms, noth- ing seems to prevent magnetoresistance from occuring for emsembles of many H atoms. This, however, still needs to be supported by a more extensive statistical analysis which is beyond the scope of this work. 

This work has been financially supported by MICINN of Spain (Grants MAT07-67845 and CONSOLIDER 

1 A. K. Geim and A. H. MacDonald, Physics Today 60 , 35 (2007). 2 

A. H. C. Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, Reviews of Modern Physics 81 , 109 (2009). 3 

T. Makarova and F. Palacio, eds., Carbon Based Mag- netism: An Overview Of The Magnetism Of Metal Free Carbon-based Compounds And Materials (Elsevier Science & Technology, 2006). 4 

S. Sorella and E. Tosatti, Europhysics Letters (EPL) 19 , 699 (1992). 5 

P. Esquinazi, D. Spemann, R. H¨ ohne, A. Setzer, K. H. Han, and T. Butz, Phys. Rev. Lett. 91 , 227201 (2003). 6 

Y. Wang, Y. Huang, Y. Song, X. Zhang, Y. Ma, J. Liang, and Y. Chen, Nano Lett. 9 , 220 (2009). 7 

M. Fujita, K. Wakabayashi, K. Nakada, and K. Kusakabe, J. Phys. Soc. Jpn. 65 , 1920 (1996). 8 

Y.-W. Son, M. L. Cohen, and S. G. Louie, Nature 444 , 347 (2006). 9 

F. Mu˜ noz-Rojas, J. Fern´ andez-Rossier, and J. J. Palacios, Physical Review Letters 102 , 136810 (pages 4) (2009). 10 

W. Y. Kim and K. S. Kim, Nature nanotechnology 3 , 408 (2008). 11 

D. Gunlycke, D. A. Areshkin, J. Li, J. W. Mintmire, and C. T. White, Nano Lett. 7 , 3608 (2007). 12 

K. Harigaya and T. Enoki, Chemical Physics Letters 351 , 128 (2002). 13 

J. Fern´ andez-Rossier and J. J. Palacios, Physical Review Letters 99 , 177204 (2007). 14 

W. L. Wang, O. V. Yazyev, S. Meng, and E. Kaxiras, Phys- ical Review Letters 102 , 157201 (pages 4) (2009). 15 

M. Ezawa, Physical Review B 77 , 155411 (2008). 16 

P. Koskinen, S. Malola, and H. H¨ akkinen, Physical Review Letters 101 , 115502 (2008). 17 

T. Wassmann, A. P. Seitsonen, A. M. Saitta, M. Lazzeri, and F. Mauri, Physical Review Letters 101 , 096402 (2008). 18 

A. Chuvilin, J. C. Meyer, G. Algara-Siller, and U. Kaiser, New Journal of Physics 11 , 083019 (2009). 19 

D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. 

## Acknowledgments 

CSD2007-00010). D.S. acknowledges financial support from Consejo Superior de Investigaciones Cient´ıficas (CSIC). 

Boukhvalov, M. I. Katsnelson, A. K. Geim, et al., Science 323 , 610 (2009). 

20 O. V. Yazyev and L. Helm, Physical Review B 75 , 125408 (2007). 21 

L. Brey, H. A. Fertig, and S. D. Sarma, Physical Review Letters 99 , 116802 (2007). 22 

S. Casolo, O. M. Løvvik, R. Martinazzo, and G. F. Tanta- rdini, The Journal of chemical physics 130 , 054704 (2009). 23 

V. R. Saunders, R. Dovesi, C. Roetti, R. Orlando, C. M. Zicovich-Wilson, N. M. Harrison, K. Doll, B. Civalleri, I. J. Bush, P. D’arco, Release 1.0.2, Theoretical Chemistry Group - Universita’ Di Torino - Torino (Italy). 24 

J. Fern´ andez-Rossier, Physical Review B (Condensed Mat- ter and Materials Physics) 77 , 075430 (2008). 25 

E. H. Lieb, Phys. Rev. Lett. 62 , 1201 (1989). 26 

J. J. Palacios, D. Jacob, A. J. P´erez-Jim´enez, E. S. Fabi´ an, E. Louis, and J. A. Verg´es, ALACANT ab-initio quantum transport package, Condensed Matter Theory Group, Uni- versidad de Alicante, URL http://alacant.dfa.ua.es . 27 

J. J. Palacios, J. Fern´ andez-Rossier, and L. Brey, Physical Review B (Condensed Matter and Materials Physics) 77 , 195428 (2008). 28 

D. Boukhvalov and M. Katsnelson, Nano Lett. 8 , 4373 (2008). 29 

J. Lin, J. J. Rhyne, J. K. Furdyna, and T. M. Giebutowicz, The 7th joint MMM-intermag conference on magnetism and magnetic materials 83 , 6554 (1998). 30 

Y.-W. Son, M. L. Cohen, and S. G. Louie, Physical Review Letters 97 , 216803 (2006). 31 

D. V. Kosynkin, A. L. Higginbotham, A. Sinitskii, J. R. Lomeda, A. Dimiev, B. K. Price, and J. M. Tour, Nature 458 , 872 (2009). 32 

H. Santos, L. Chico, and L. Brey, Physical Review Letters 103 , 086801 (pages 4) (2009). 33 

A. Javey, J. Guo, D. B. Farmer, Q. Wang, D. Wang, R. G. Gordon, M. Lundstrom, and H. Dai, Nano Letters 4 , 447 (2004). 34 

C. P. Herrero and R. Ramirez, Physical Review B 79 , 115429 (2009). 

