Magnetised graphene could lead to spintronic devices

The findings, from the Madrid Institute for Advanced Studies in Nanoscience (IMDEA-Nanociencia) and Autonoma Autonomous (UAM) and Complutense (UCM) universities of Madrid, have been published in Nature Physics.

‘In spite of the huge efforts to date of scientists all over the world, it has not been possible to add the magnetic properties required to develop graphene-based spintronics. However these results pave the way to this possibility,’ said Prof Rodolfo Miranda, director of IMDEA-Nanociencia.

Spintronics is based on the charge of the electron and its spin, which determines its magnetic moment. As the spin can have two values, its use adds two more states to traditional electronics; both data processing speed and quantity of data to be stored on electronic devices can be increased, with applications in fields including telecommunications, computing, energy and biomedicine.

In order to develop a graphene-based spintronic device, the challenge was to ‘magnetise’ the material, and researchers from Madrid claim to have found the way through the quantum and nanoscience world.

According to the team, the technique involves growing an ultra perfect graphene film over a ruthenium single crystal inside an ultra high vacuum chamber where organic molecules of tetracyano-p-quinodimethane (TCNQ) are evaporated on the grapheme surface. TCNQ is a molecule that acts as a semiconductor at very low temperatures in certain compounds.

On observing results through an scanning tunnelling microscope, the scientists found that organic molecules had organised themselves and were regularly distributed all over the surface, interacting electronically with the graphene-ruthenium substrate.

‘We have proved in experiments how the structure of the TCNQ molecules over graphene acquires long-range magnetic order, with electrons positioned in different bands according to their spin,’ said Prof Amadeo L. Vázquez de Parga in a statement.

Prof Fernando Martin has conducted modelling studies that have shown that, although graphene does not interact directly with the TCNQ, it does permit a highly efficient charge transfer between the substrate and the TCNQ molecules and allows the molecules to develop long range magnetic order.

The result is a new graphene-based magnetised layer, which paves the way towards the creation of devices based on what was already considered as the material of the future, but which now may also have magnetic properties.