Record-high magnetoresistance appears in graphene under ambient conditions, according to new research led by the University of Manchester.
Materials that strongly change their resistivity under magnetic fields are highly sought for various applications and, for example, every car and every computer contain many tiny magnetic sensors.
Such materials are rare, and most metals and semiconductors change their electrical resistivity only by a tiny fraction of a percent at room temperature and in practically viable magnetic fields (typically, by less than a millionth of 1 %).
To observe a strong magnetoresistance response, researchers usually cool materials to liquid-helium temperatures so that electrons inside scatter less and can follow cyclotron trajectories.
In the new research, Professor Sir Andre Geim and colleagues found that graphene exhibits a remarkably strong response, reaching above 100% in magnetic fields of standard permanent magnets (of about 1,000 Gauss). This is a record magnetoresistivity among all the known materials.
“People working on graphene like myself always felt that this gold mine of physics should have been exhausted long ago,” Professor Sir Geim said.
“The material continuously proves us wrong finding yet another incarnation. Today I have to admit again that graphene is dead, long live graphene.”
To achieve this, the researchers used high-quality graphene and tuned it to its intrinsic, virgin state where there were only charge carriers excited by temperature.
This created a plasma of fast-moving Dirac fermions that exhibited a surprisingly high mobility despite frequent scattering.
Both high mobility and neutrality of this Dirac plasma are crucial components for the reported giant magnetoresistance.
“Over the last 10 years, electronic quality of graphene devices has improved dramatically, and everyone seems to focus on finding new phenomena at low, liquid-helium temperatures, ignoring what happens under ambient conditions,”…
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