Spintronics: little crystallized hurricanes

Quasi-particles made up of a collection of electron spins can be ordered into a crystal lattice at near room temperature. Fig. 1: Spin map showing the formation of a skyrmion lattice in thin

films of iron–germanium at near room temperatureFrom Ref. 1 © 2011 Y. Tokura, X. Z. Yu Electrons are characterized by their mass, their charge and a third property called spin related to

their angular momentum. Electron spin is an ideal medium for manipulating, transporting and storing information, and its exciting potential has led to the rapid development of the field of

spintronics. In a solid, spins can also organize into complex but stable structures that behave just as if they were single particles. And, just as with real particles, they can be arranged

into periodic crystals. Yoshinori Tokura and co-workers from the University of Tokyo, the Japan Science and Technology Agency, the National Institute for Material Science and RIKEN in Japan1

have now created such a crystal at temperatures higher than achieved previously, and high enough to be used in spintronic devices operating at near room temperature. One example of these

strange quasi-particles is the skyrmion, in which the spins point around a series of concentric circles. This is similar to a map of the air flow in a hurricane, but in a skyrmion the spins

on the outside point up and those at the center point down. Scientists have predicted that a repeating lattice of these structures — a skyrmion crystal (pictured) — could prove to be

advantageous for spintronics. “Skyrmions couple strongly with electromagnetic fields and can therefore give rise to unusual electromagnetic properties,” says Tokura. Researchers have

previously seen the skyrmion-crystal state in transition-metal–silicide materials at temperatures below 40 K. But crystals at or near room temperature are needed if the idea is to be applied

to real devices. Tokura and his colleagues have now achieved this for the first time using thin films of iron–germanium — a material that is similar to those studied previously but

maintains the necessary magnetic structure at up to 280 K. One technology that could potentially benefit from this development is magnetic random access memory, in which information is

stored in terms of the magnetic properties in small domains. “It has recently been reported that the electric-current threshold for the motion of a skyrmion crystal is smaller than that for

a magnetic domain wall,” explains Tokura. REFERENCES * Yu, X. Z., Kanazawa, N., Onose, Y., Kimoto, K., Zhang, W. Z., Ishiwata, S., Matsui, Y. & Tokura, Y. Near room-temperature formation

of a skyrmion crystal in thin-films of the helimagnet FeGe. _Nature Mater._ 10, 106–109 (2011); doi:10.1038/nmat2916 Article  CAS  Google Scholar  Download references ADDITIONAL INFORMATION

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