Controlling the magnetic properties of graphene
April 15, 2011
Researchers at the University of Maryland have discovered a way to control magnetic properties of graphene that could lead to new applications in magnetic storage and magnetic random access memory.
The researchers found that missing atoms in graphene, called vacancies, act as tiny magnets. Vacancies have magnetic moments that interact strongly with the electrons in graphene, which carry electrical currents. This gives rise to a significant extra electrical resistance at low temperature, known as the Kondo effect, which is typically associated with adding tiny amounts of magnetic metal atoms, such as iron or nickel, to a non-magnetic metal, such as gold or copper.
The team measured the characteristic temperature for the Kondo effect in graphene with vacancies as high as 90 degrees Kelvin, which is comparable to that seen in metals with very high electron densities. The Kondo temperature can be tuned by the voltage on an electrical gate, an effect not seen in metals.
The researchers theorized that the same unusual properties that result in graphene’s electrons acting as if they have no mass also make them interact very strongly with certain kinds of impurities, such as vacancies, leading to a strong Kondo effect at a relatively high temperature. They also suggested that ferromagnetism could result if vacancies in graphene could be arranged in just the right way.
When coupled with graphene’s electrical properties, magnetism in graphene could have interesting applications in the area of spintronics, the researchers said.
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