The incorporation of magnetism to the long list of graphene capabilities has been pursued since its first isolation in 2004. The use of spin as an additional degree of freedom would represent a tremendous boost to the versatility of graphene based devices. On one hand, spin information transfer or spin diffusion phenomena are favored by the expected long spin relaxation times of graphene carriers. On the other, as we show here, graphene magnetism and charge transport can take place in the same pi bands and thus a major potential in future spintronics applications can be anticipated.
This work visualizes, for the first time, how the absorption of single H atoms on graphene magnetizes the graphene regions around them. In contrast to common magnetic materials, where the magnetic moments are localized in a few angstroms, the induced graphene magnetic moments extend over several nanometers and present an atomically modulated spin texture. Our measurements also prove that the induced magnetic moments couple strongly at very long distances following a particular rule: magnetic moments sum-up or neutralize critically depending on the relative H-H adsorption sites. Furthermore, and equally important, we achieve the controlled manipulation of single H atoms, which enable us to selectively tune the collective magnetic properties of chosen graphene regions.
Since the early days of graphene research, all theoretical predictions agree that graphene can be magnetized at will by the adsorption of single hydrogen atoms. However, experimental efforts to provide a direct proof of such remarkable predictions have so far been unsuccessful, mainly due to the difficulties of providing, at the same time, an atomistic characterization and control of the hydrogenated graphene samples. We have now overcome these challenges going even beyond theoretical expectations. The unexpected possibility to arrange H atoms on graphene with any desired geometry will enable the realization experiments restricted so far to a pure theoretical framework. For example, the magnetization of selected graphene areas will allow for injection of spin currents in-situ, avoiding the use of ferromagnetic electrodes and thus the long-standing problems associated with ferromagnet-graphene contacts. Likewise, the possibilities of creating spin valves and magnetoresistive devices entirely made of carbon anticipate unlimited uses of graphene in spintronics. [Full article]
We have prepared a didactic video explaining our results:
Héctor González-Herrero, José María Gómez-Rodríguez, Pierre Mallet, Mohammed Moaied, Juan José Palacios, Carlos Salgado, Miguel M. Ugeda, Jean-Yves Veuillen, Félix Ynduráin and Iván Brihuega.