Graphene shows record-breaking magnetic properties at room temperature

Nearly 20 years after graphene was discovered, research suggests that it is the most magnetoresistive material we know of. This represents the ability to increase or decrease electrical resistance in response to a magnetic field, and may one day be applied to data storage methods.

Arranged as sheets of carbon atoms in a honeycomb structure, graphene (a two-dimensional material extracted from graphite) was already known to be stronger than diamond and capable of conducting electricity better than copper.

Now, André Geim and his colleagues at the University of Manchester, UK, have discovered that it also has unprecedented magnetoresistance at room temperature.

To find out, the team first applied an electric field to some graphene to equalize the number of charge carriers responsible for generating current in the material. These carriers consist of negatively charged electrons and positively charged holes.

Pure graphene with no defects in the honeycomb structure has the same number of electrons and holes. Since such graphene is difficult to produce, the research team used an electric field to tune the structure of defective graphene, allowing the material to be studied in a more pure state.

Geim, who won the Nobel Prize in Physics in 2010 for his work on graphene, says that defects in a material’s structure affect its magnetoresistance.

The researchers then applied different magnetic fields to graphene and measured how its magnetoresistance changed. Even a small magnetic field changed its electrical resistance dramatically.

This is because electrons and holes in graphene are highly mobile and sensitive to small changes in external magnetic fields, the researchers wrote in their paper.

Most materials exhibit magnetoresistance only at very low temperatures. In this experiment, the researchers said, graphene was more magnetoresistive at room temperature than any other material tested in previous studies, including graphite and bismuth.

Magnetoresistive materials are already used in data storage devices to interpret information stored as tiny magnetic patterns on tapes and disks. Researchers plan to continue working with graphene and its “applications continue,” said Leonid Ponomarenko, a researcher at Lancaster University in the UK, in a statement.

Antonio Hélio Castro Neto of the National University of Singapore says the discovery could open the door to exploring fundamental physics.

Because graphene is a two-dimensional material, the movement of these charge carriers is confined to thin layers, he says.

“In this regime, the interactions between holes and electrons become very strong, and there is room for further study of what controls these interactions and governs them,” says Castro Neto.