Materials

Scientists give graphene one more quality – magnetism

Scientists give graphene one m...
A diagram of the magnetized graphene (Image: Shi Lab, UC Riverside)
A diagram of the magnetized graphene (Image: Shi Lab, UC Riverside)
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A diagram of the magnetized graphene (Image: Shi Lab, UC Riverside)
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A diagram of the magnetized graphene (Image: Shi Lab, UC Riverside)

Graphene is extremely strong for its weight, it's electrically and thermally conductive, and it's chemically stable ... but it isn't magnetic. Now, however, a team from the University of California, Riverside has succeeded in making it so. The resulting magnetized graphene could have a wide range of applications, including use in "spintronic" computer chips.

While other groups have previously magnetized graphene, they've done so by doping it with foreign substances, and the presence of these impurities has negatively affected its electronic properties. In this case, though, the graphene was able to remain pure.

Led by professor of physics and astronomy Jing Shi, the UC Riverside team laid a sheet of regular graphene down on an atomically smooth layer of magnetic yttrium iron garnet. That material then simply magnetized the graphene as it lay against it. Yttrium iron garnet was used due to the fact that certain other magnetic materials could disrupt the graphene’s electrical transport properties.

When the sheet of graphene was removed and subsequently exposed to a magnetic field, it was shown to indeed possess magnetic qualities of its own.

"This is the first time that graphene has been made magnetic this way," said Shi. "The magnetic graphene acquires new electronic properties so that new quantum phenomena can arise. These properties can lead to new electronic devices that are more robust and multi-functional."

Those devices could include improved spintronic chips, that use the spin of electrons – which can be magnetically manipulated – to store data.

A paper on the research was recently published in the journal Physical Review Letters.

Source: University of California, Riverside

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Hemp fibres 'better than graphene' By fabricating these sheets into electrodes and adding an ionic liquid as the electrolyte, his team made supercapacitors which operate at a broad range of temperatures and a high energy density. Direct comparisons with rival devices are complicated by the variety of measures for performance. But Mitlin's peer-reviewed journal paper ranks the device "on par with or better than commercial graphene-based devices". "They work down to 0C and display some of the best power-energy combinations reported in the literature for any carbon. "For example, at a very high power density of 20 kW/kg (kilowatt per kilo) and temperatures of 20, 60, and 100C, the energy densities are 19, 34, and 40 Wh/kg (watt-hours per kilo) respectively." tall hemp plants Fully assembled, their energy density is 12 Wh/kg, which can be achieved at a charge time less than six seconds. Growth industry "Obviously hemp can't do all the things graphene can," Dr Mitlin concedes. "But for energy storage, it works just as well. And it costs a fraction of the price -$500-1,000 a tonne."