Twisted Graphene Exhibits Previously Theoretical Magnetic State With Great Potential

The “wonder material” known as graphene continues to prove its merits in unexpected ways as scientists and engineers experiment with new applications. In an accidental discovery at Stanford, graphene exhibited a magnetic property that was previously considered theoretical and could someday lead to important advancements in storage technologies.

Without even a shred of hyperbole, graphene is an incredible material. Made up of carbon atoms arranged in a hexagonal lattice, the material is no more than an atom thick, nearly transparent, and about 100 times stronger than steel. Although difficult to produce at scale (for now), you can (sort of) make it with a no. 2 pencil and a strip of tape. Recent discoveries demonstrated that graphene conducts electricity with no resistance when arranged in a twisted bilayer arrangement and provides a path toward the development of super-fast electronics. As New Atlas reports, a team at Stanford decided to build upon this discovery and inadvertently made one of their own.

When the team took a graphene sample and provided it with electric current, it produced a large voltage flowing perpendicular to that current. Even in the absence of an external magnetic field, the graphene continued to internally generate its own. While materials will most commonly exhibit ordinary ferromagnetism upon the synchronization of their electron’s spin states, the internal magnetic field achieved with the graphene sample displayed orbital ferromagnetism—a previously theoretical phenomenon caused by the alignment of orbital motion in a material’s electrons.

Two key changes caused the discovery: sandwiching the twisted bilayer graphene between thin, aligned layers of thin hexagonal boron nitride and an increase in the rotation of the graphene sheets from 1.1 to 1.2 degrees. Although the graphene sample couldn’t accomplish much of what you’d expect from an everyday magnet, lead researcher David Goldhaber-Gordon explains how this actually presents an advantage:

Our magnetic bilayer graphene can be switched on with very low power and can be read electronically very easily. The fact that there’s not a large magnetic field extending outward from the material means you can pack magnetic bits very close together without worrying about interference.

Densely packed magnetic bits and a low energy footprint offer a potential solution to the high costs of data centers that make up for 2 percent of yearly power consumption in the United States. To put that in perspective, that electricity could power roughly 6.4 million homes. Furthermore, greater bit density can lead to increases in storage capacity and a smaller surface area.

Back in 2012, IBM devised a system of storing one bit across 12 atoms—a little less than a typical storage device that requires about a million. IBM accomplished this feat using antiferromagnetism, though it seems that graphene’s orbital ferromagnetism and low power requirements might become a more useful home for such a storage system. After all, they built a super-fast graphene processor a couple of years later. Perhaps Stanford’s efforts will lead to super-fast chips with long-term memory storage—a combination worthy of a synapse-emulating photonic microchip. Light might even speed things up further, too.

Of course, fun ideas like that live in a speculative world of imagination—at least until graphene gives us another happy accident. But that’s part of what makes graphene such a wonder material: you can boldly dream about its potential and, sometimes, it will suddenly deliver the reality.

Title image credit: Adam Dachis

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