Graphite mimics iron's magnetism

October 04, 2009

Researchers of Eindhoven University of Technology and the Radboud University Nijmegen in The Netherlands show for the first time why ordinary graphite is a permanent magnet at room temperature. The results are promising for new applications in nanotechnology, such as sensors and detectors. In particular graphite could be a promising candidate for a biosensor material. The results will appear online on 4 October in Nature Physics.

Graphite is a well-known lubricant and forms the basis for pencils. It is a layered compound with a weak interlayer interaction between the individual carbon (graphene) sheets. Hence, this makes graphite a good lubricant.


It is unexpected that graphite is ferromagnetic. The researchers Jiri Cervenka and Kees Flipse (Eindhoven University of Technology) and Mikhail Katsnelson (Radboud University Nijmegen) demonstrated direct evidence for ferromagnetic order and explain the underlying mechanism. In graphite well ordered areas of carbon atoms are separated by 2 nanometer wide boundaries of defects. The electrons in the defect regions (the red/yellow area in picture 1) behave differently compared to the ordered areas (blue in picture 1), showing similarities with the electron behaviour of ferromagnetic materials like iron and cobalt.

Debate settled

The researchers found that the grain boundary regions in the individual carbon sheets are magnetically coupled, forming 2-dimensional networks (picture 2). This interlayer coupling was found to explain the permanent magnetic behaviour of graphite. The researchers also show experimental evidence for excluding magnetic impurities to be the origin of ferromagnetism, ending ten years of debate.

Carbon in spintronics

Surprisingly, a material containing only carbon atoms can be a weak ferro magnet. This opens new routes for spintronics in carbon-based materials. Spins can travel over relative long distances without spin-flip scattering and they can be flipped by small magnetic fields. Both are important for applications in spintronics. Carbon is biocompatible and the explored magnetic behaviour is therefore particularly promising for the development of biosensors.
Publication Nature Physics

The paper in Nature Physics " Room-temperature ferromagnetism in graphite driven by 2D networks of point defects" by Jiri Cervenka, Mikhail Katsnelson and Kees Flipse will appear online Sunday 4 October, 7:00 pm CET. The paper can be found under DOI 10.1038/NPHYS1399.

The research was funded by Nanoned and FOM.

Eindhoven University of Technology

Related Spintronics Articles from Brightsurf:

A four-state magnetic tunnel junction for novel spintronics applications
Researchers have introduced a new type of MTJ with four resistance states, and successfully demonstrated switching between the states with spin currents.

Ultrafast electrons in magnetic oxides: A new direction for spintronics?
Special metal oxides could one day replace semiconductor materials that are commonly used today in processors.

Efficient valves for electron spins
Researchers at the University of Basel in collaboration with colleagues from Pisa have developed a new concept that uses the electron spin to switch an electrical current.

Magnetic memory states go exponential
Researchers showed that relatively simple structures can support exponential number of magnetic states - much greater than previously thought - and demonstrated switching between the states by generating spin currents.

New breakthrough in 'spintronics' could boost high speed data technology
Scientists have made a pivotal breakthrough in the important, emerging field of spintronics -- which could lead to a new high speed energy efficient data technology.

A path to new nanofluidic devices applying spintronics technology
Japanese scientists have elucidated the mechanism of the hydrodynamic power generation using spin currents in micrometer-scale channels, finding that power generation efficiency improves drastically as the size of the flow is made smaller.

Extensive review of spin-gapless semiconductors: Next-generation spintronics candidates
An Australian has published an extensive review of spin-gapless semiconductors (SGSs), a new class of 'zero bandgap' materials which have fully spin polarised electrons and holes, and first proposed in 2008 by the review team's lead, Professor Xiaolin Wang (University of Wollongong).

Graphene and 2D materials could move electronics beyond 'Moore's Law'
A team of researchers based in Manchester, the Netherlands, Singapore, Spain, Switzerland and the USA has published a new review on a field of computer device development known as spintronics, which could see graphene used as building block for next-generation electronics.

Toward a more energy-efficient spintronics
In order to generate and detect spin currents, spintronics traditionally uses ferromagnetic materials whose magnetization switching consume high amounts of energy.

Computing with molecules: A big step in molecular spintronics
Chemists and physicists at Kiel University joined forces with colleagues from France, and Switzerland to design, deposit and operate single molecular spin switches on surfaces.

Read More: Spintronics News and Spintronics Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to