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Graphene Becomes Magnetic and Electric at Same Time

Imbuing graphene with magnetism used to sacrifice its electrical properties, but not anymore

2 min read
Graphene Becomes Magnetic and Electric at Same Time
Illustration: Randi Klett

Combining the electric with the magnetic in one material has become a hot research pursuit lately. First researchers exploited the natural properties of bismuth ferrite. Then researchers engineered both electric and magnetic polarization in perovskite—a material that does not have that property naturally.

Now researchers at the University of California Riverside have brought this combination of the electric and the magnetic to the wonder material, graphene.

Of course, it is possible to induce magnetism in graphene by doping the material with magnetic impurities. Unfortunately, that process comes at the high cost of eliminating all the attractive electrical properties of graphene, such as its high conductivity.

The UC Riverside researchers found a way to make graphene magnetic without sacrificing its attractive electrical properties.

“This is the first time that graphene has been made magnetic this way,” said Jing Shi, a professor of physics and astronomy, whose lab led the research, in a press release. “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.”

In research published in the journal Physical Review Letters,  the UC Riverside researchers were able to achieve this feat by bringing a sheet of graphene very close to a magnetic insulator—an electrical insulator with magnetic properties.

In this case, the magnetic insulator was an atomically flat yttrium iron garnet (YIG) ferromagnetic thin film that the researchers had actually grown using laser molecular beam epitaxy.

With the graphene so close to the iron-based magnetic insulator, the graphene simply borrowed its magnetic properties. The trick was to ensure that the graphene adopted the magnetic properties without losing its electrical ones. Because the yttrium iron garnet is an electric insulator it did not disrupt graphene’s electrical transport properties.

In experiments, the research team demonstrated that the graphene had become magnetic by exposing it to an external magnetic field at which time it revealed graphene's Hall voltage—a voltage in the perpendicular direction to the current flow—was linearly dependent on the magnetization of the yttrium iron garnet. This provided the confirmation that the graphene sheet had turned magnetic.

As we have seen with other materials recently, the combination of both electrical and magnetic properties in one material opens up possibilities in information storage, especially through the use of spintronics.

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3 Ways 3D Chip Tech Is Upending Computing

AMD, Graphcore, and Intel show why the industry’s leading edge is going vertical

8 min read
A stack of 3 images.  One of a chip, another is a group of chips and a single grey chip.
Intel; Graphcore; AMD

A crop of high-performance processors is showing that the new direction for continuing Moore’s Law is all about up. Each generation of processor needs to perform better than the last, and, at its most basic, that means integrating more logic onto the silicon. But there are two problems: One is that our ability to shrink transistors and the logic and memory blocks they make up is slowing down. The other is that chips have reached their size limits. Photolithography tools can pattern only an area of about 850 square millimeters, which is about the size of a top-of-the-line Nvidia GPU.

For a few years now, developers of systems-on-chips have begun to break up their ever-larger designs into smaller chiplets and link them together inside the same package to effectively increase the silicon area, among other advantages. In CPUs, these links have mostly been so-called 2.5D, where the chiplets are set beside each other and connected using short, dense interconnects. Momentum for this type of integration will likely only grow now that most of the major manufacturers have agreed on a 2.5D chiplet-to-chiplet communications standard.

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