Ferromagnetic thin film induces magnetism in graphene
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Ferromagnetic thin film induces magnetism in graphene
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ver the past decade, graphene has become one of the most intensely investigated materials. Graphene shows high electrical conductivity, and understanding the electrical properties of high-quality graphene under different conditions is a topic of great interest. In an article recently published in the January 7 issue of Physical Review Letters (DOI: 10.1103/PhysRevLett.114.016603), researchers at the University of California–Riverside have determined a way to induce ferromagnetism in graphene, opening a new path of investigation especially into its spintronics applications. “Graphene has many interesting properties,” said Jing Shi, professor of physics at the University of California–Riverside. “It’s especially unusual compared to other conducting materials. And now it’s even more unusual that we know what it exhibits with an anomalous Hall effect.” The ordinary Hall effect is equivalent to a magnetic field sensor, meaning that it can be used to measure the direction and strength of a magnetic field. A material that shows the anomalous Hall effect is sensitive to the direction of magnetization of a magnetic material. The idea behind the present work is that attaching a magnetic material to graphene can make graphene ferromagnetic, which can induce the anomalous Hall effect. By measuring shifts in the Hall effect, researchers can better understand the properties of a material or the interactions between two materials. A standalone graphene sheet has been known to exhibit diamagnetism, said Shi. But such magnetism is not very useful for
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VOLUME 40 • MARCH 2015
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Technology and Design. Skylar Tibbits at MIT’s Self-Assembly Laboratory also contributed significantly. Their work anticipates developments in—and increasing use of—soft robotics, where this has many potential applications in vivo. A thermally activated stent, for example, could be printed and inserted
into a collapsed artery where it would expand and open the artery on its own. The confluence of materials science, 3D printing technology, and computational engineering heralds a future in which these active, self-evolving structures find many invaluable uses. Antonio Cruz
electronic device applications. Attempts to create magnetism in graphene by doping have not been very successful, and would also hurt graphene’s excellent electrical transport properties. Shi and his group decided to attempt A single layer of graphene on top of a ferromagnetic yttrium iron to induce magnetism garnet (YIG) thin film. Together, they create an anomalous Hall effect. Credit: Jing Shi. by attaching a single layer of graphene to an yttrium iron garnet (YIG) thin film. that the Hall effect was indeed present This film is magnetic up to 550 K. An in the graphene, meaning that YIG had important aspect of the YIG thin film is induced magnetization in the graphene that it is an insulator, so it would not disheet. The Hall effect senses the magvert electric current away and thus affect netization (or electron
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