European project HiMagGraphene "The magnetism of graphene can be controlled with hydrogen atoms" - SINC
Graphene has extraordinary mechanical and electronic properties, but not magnetic ones. This deficiency can be resolved with the help of the lightest of the elements: hydrogen, which, when in contact with graphene, transfers its magnetic moment to it. It has been demonstrated by a team of European scientists coordinated by the physicist Iván Brihuega from the Autonomous University of Madrid.
Enrique Sacristan 11/30/2017 11:45 CEST
Part of the HiMagGraphene project team next to the scanning tunneling microscope with which the experiments have been carried out. On the left, Iván Brihuega, with other scientists from the Autonomous University of Madrid and the Institut Néel in France. /UAM/HiMagGraphene
Since graphene was obtained for the first time in 2004, laboratories around the world have tried to incorporate magnetism into the long list of properties offered by this two-dimensional material made up of carbon atoms.
Within the European Graphene Flagship initiative , three research groups from Spain, France and Germany have begun to experimentally demonstrate that graphene can be magnetized at will through the adsorption of individual hydrogen (H) atoms.
The project, called HiMagGraphene, is coordinated by Professor Iván Brihuega (Madrid, 1975) from the Department of Condensed Matter Physics at the Autonomous University of Madrid (UAM).
What happens when graphene and hydrogen come together?
The results achieved so far in our project reveal that if a hydrogen atom touches a layer of graphene, it transfers its magnetic moment to it. Contrary to what happens with the most common magnetic materials, such as iron, nickel or cobalt, where the magnetic moment generated by each atom is located within a few tenths of a nanometer, the magnetic moment induced in graphene by each atom of hydrogen extends several nanometers and we can modulate it on an atomic scale.
"The magnetic moment induced in graphene by each hydrogen atom extends several nanometers and we can modulate it on an atomic scale"
What exactly happens during the process?
The induced magnetic moments strongly interact with each other at great distances (compared to the atomic scale) following, in addition, a particular rule: these moments are added or neutralized depending on the relative position occupied by the hydrogen atoms on the material. The structure of graphene, made up of carbon atoms arranged in a hexagonal shape, can be considered as two triangular sub-lattices, and if the hydrogen atoms are placed in only one of them, their magnetic moments add up. However, they cancel out when we put one hydrogen atom in one sublattice and another in the other.
How do you move hydrogen atoms?
Using a powerful scanning tunneling microscope, with which these atoms can be viewed and manipulated individually. Thus, the magnetic properties of selected regions of the graphene are set at will. We have carried out the experiments entirely at the Institute of Condensed Matter Physics (IFIMAC) of the UAM, and the results have been complemented with sophisticated theoretical calculations. We presented the details last year in the journal Science .
Have you published more papers related to the project?
In 2016, together with colleagues from the Basque Country, we also presented another study at ACS Nano in which we showed that when a metallic substrate is placed under graphene, some of its properties change. Specifically, the possibility of inducing magnetic moments with hydrogen atoms disappears. And in 2017 we published in The Journal of Physical Chemistry B a paper on the selective adsorption of hydrogen in bilayers of rotated graphene.
What other groups participate in HiMagGraphene, besides yours?
Two more. One is at the Institut Néel de Grenoble (CNRS, France), which provides different types of graphene samples grown on silicon carbide. And the other is the German group at the Max-Planck-Institute (MPI) in Stuttgart, which has a unique tunneling microscope infrastructure. The collaboration with them focuses on making measurements at very low temperatures (less than 1 Kelvin) and with high magnetic fields (up to 14 Tesla).
“Being able to manufacture magnetic graphene would make it possible to have magnetic tissues and nanoparticles to treat cancer”
In what phase of the project are you now?
HiMagGraphene is a three-year project ending in November 2018. We are currently studying how to massively manipulate H atoms on the graphene surface with atomic precision to selectively modify its properties. We also investigate the evolution of the magnetic moment induced in this material by the hydrogen atoms –what we call the spin -polarized state– as a function of two factors: the applied magnetic field and the temperature of the sample.
Is spintronics one of the potential applications of graphene?
Yes. A priori, it is an ideal material for use in spintronics, a promising technology that aims to replace traditional electronics, transmitting magnetic information through spin and electronics at the same time. This could give rise to a radically new generation of computers. The results of our project, which show the possibility of generating magnetic moments at will and that can be communicated over great distances in graphene, anticipate a bright future for this material, both in the emerging field of spintronics and for its use in devices. flexible and biocompatible magnets. In addition, the fact of being able to manufacture magnetic graphene would make it possible to have anything from plastics or even magnetic tissues, to nanoparticles to treat cancer.
Magnetic moments are generated when hydrogen atoms bind to carbon atoms in the graphene lattice, which comprises two sublattices. Moments align ferromagnetically (blue) when they are on the same sublattice and antiferromagnetically (orange) when they are on the opposite sublattice. / C. Bickel/Science
Source: SINC