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Posted on April 29, 2011 by  & 

New spin on graphene

Scientists including an MIT physics professor have found a way to make wonder material graphene magnetic, opening up a new range of opportunities for the world's thinnest material in the area of spintronics.
The collaboration, led by the University of Manchester, showed that electric current — a flow of electrons — can magnetize graphene. The results, reported in the April 15 issue of Science, could be a potentially huge breakthrough in the field of spintronics.
MIT physics professor Leonid Levitov is a member of the research team, along with scientists from Princeton, the Netherlands and Japan.
Spintronics is a group of emerging technologies that exploit the intrinsic spin of the electron, in addition to its fundamental electric charge that is exploited in microelectronics.
Billions of spintronics devices such as sensors and memories are already being produced. Every hard disk drive has a magnetic sensor that uses a flow of spins, and magnetic random access memory (MRAM) chips are becoming increasingly popular.
The key feature for spintronics is to connect the electron spin to electric current as current can be manipulated by means routinely used in microelectronics.
It is believed that, in future spintronics devices and transistors, coupling between the current and spin will be direct, without using magnetic materials to inject spins as it is done at the moment.
So far, this route has only been demonstrated by using materials with so-called spin-orbit interaction, in which tiny magnetic fields created by nuclei affect the motion of electrons through a crystal. The effect is generally small which makes it difficult to use.
The researchers found a new way to interconnect spin and charge by applying a relatively weak magnetic field to graphene and found that this causes a flow of spins in the direction perpendicular to electric current, making a graphene sheet magnetized.
The effect resembles the one caused by spin-orbit interaction but is larger and can be tuned by varying the external magnetic field.
The researchers also show that graphene placed on boron nitride is an ideal material for spintronics because the induced magnetism extends over macroscopic distances from the current path without decay.
The team believes their discovery offers numerous opportunities for redesigning current spintronics devices and making new ones such as spin-based transistors.
"The holy grail of spintronics is the conversion of electricity into magnetism or vice versa," said Professor Andre Geim of the University of Manchester, senior author of the paper. "We offer a new mechanism, thanks to unique properties of graphene. I imagine that many venues of spintronics can benefit from this finding."
Source: "Giant Nonlocality Near the Dirac Point in Graphene," by D.A Abanin, S.V.Morozov, L. A Ponomarenko, R.V Gorbachev, A.S Mayorov, M.I Katsnelson, Kenji Watanabe, Takashi Taniguchi, K.S Novoselov, L.S Levitov and A.K Geim and Massachusetts Institute of Technology.
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