New magnetism found in the world’s toughest material

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Graphene, one of the strongest materials in the world, is not normally magnetic. But when stacked and twisted, graphene develops a rare form of magnetism, according to new research.

The magnetic field is not created by the usual rotation of electrons in the individual layers of graphene, but rather results from the collective vortex of electrons in all three layers of the stacked graphene structure, the researchers reported on Oct. 12 in the newspaper. Physics of nature.

Graphene is a material made up of a single layer (or monolayer) of carbon atoms arranged in a honeycomb. It is incredibly light and strong (although it is vulnerable to cracking). It also conducts electricity, which makes it attractive for use in electronics and sensors.

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“We wondered what would happen if we combined monolayers and bilayers of graphene in a twisted three-layer system,” Cory Dean, a physicist at Columbia University in New York and one of the lead authors of the new paper , said in a press release. “We have found that varying the number of graphene layers gives these composite materials exciting new properties that have never been seen before.”

Dean and his colleagues stacked two layers of graphene, then added a single layer on top, rotating the stack by 1 degree. They then studied this graphene sandwich under a variety of circumstances, including temperatures just above absolute zero (the point at which all molecular motion stops). At these low temperatures, they found that graphene stopped conducting electricity and became an insulator instead.

They also found that they could control the properties of the meandering graphene stack by applying a electric field. When the electric field was oriented in one direction, the system acted as a twisted double layer of graphene. When they reversed the field, the stack took on the properties of a four-layer twisted graphene structure.

Perhaps the strangest of all was the rare magnetism that appeared in the three-layered structure. A study published by another group in the journal Advanced materials discovered that graphene binds to boron nitride can give rise to a strange magnetic field; this field is born from the molecular bonds of carbon in graphene and boron in boron nitride. The new research reveals that this same type of magnetism can occur in pure graphene alone, simply because of interactions between carbon molecules.

“Pure carbon is not magnetic,” study co-author Matthew Yankowitz, a physicist at the University of Washington in Seattle, said in the statement. “Remarkably, we can design this property by arranging our three graphene sheets at the right angles of twist. ”

The structure also contains regions where the properties are not disturbed by the twisting of the layer. These unique areas of the material could be exploited for data storage or quantum computing applications, study co-author Xiaodong Xu, also at the University of Washington, said in the statement.

Researchers now plan to delve into the fundamental properties of the structure of graphene. “This is really just the start,” Yankowitz said.

Originally posted on Live Science.


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