Magnetic skyrmions found to hold the potential of storing electronic data

November 16, 2017 by Bob Yirka, Phys.org report
Magnetic whorls. A target skyrmion is a pattern of spins in a material (gray disks) that includes two components (shown below each disk): a “normal” circular skyrmion (middle level) and a ring of spins that produces an opposing magnetic field (bottom level). The pattern comes in two states, “down” (left) and “up” (right). Credit: Physics

(Phys.org)—A team of researchers with members from the U.S., Germany and China has found that magnetic skyrmions could one day be used as a means of storing electronic data. In their paper published in the journal Physical Review Letters, the researchers describe creating a structure capable of generating skyrmions that can be reversed with a magnet while retaining its form as the magnet is withdrawn.

Skyrmions are swirling spins in a material that exist as a pattern, generally a circle, and are typically stabilized by use of an external magnet. In this new effort, the researchers developed a method by which skyrmions could be generated that do not require an external magnet to remain stable. Furthermore, they found that applying a magnet caused the to reverse itself.

To generate a skyrmion, the researchers created an iron germanide disk (using ion beam milling and gas injection followed by etching) with a 160-nanometer diameter that was 90 nanometers thick. They then used to show that a skyrmion existed in the middle of the disk they had created. They also found that the outer part of the disk held that created a that was opposite to that of the skyrmion. Further study of the structure they created showed that it had two lowest ground state configurations—one with the skyrmion rotating clockwise (with the spins pointing up), the other counterclockwise (with the spins pointing down). The skyrmion, they also found, could shift between the two states by temporarily applying a magnetic field as small as 200 millitesla. The stabilization, the researchers suggest, occurs because of the magnetic field generated by the outer ring of the disk

In noting that the skyrmion could be switched back and forth quickly and easily, the researchers suggest the structure could be applied in a replacement for conventional memory devices, because it is much smaller than ferromagnetics now in use. They also point out the possibility of using them to create logic gates. Techniques for simplifying and industrializing the process of creating the disks would have to be developed before implementation of such applications, however.

Explore further: Neutron scattering clarifies the arrangement of skyrmions in material

More information: Fengshan Zheng et al. Direct Imaging of a Zero-Field Target Skyrmion and Its Polarity Switch in a Chiral Magnetic Nanodisk, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.119.197205 . On Arxiv: https://arxiv.org/abs/1706.06923

ABSTRACT
A target Skyrmion is a flux-closed spin texture that has twofold degeneracy and is promising as a binary state in next generation universal memories. Although its formation in nanopatterned chiral magnets has been predicted, its observation has remained challenging. Here, we use off-axis electron holography to record images of target Skyrmions in a 160-nm-diameter nanodisk of the chiral magnet FeGe. We compare experimental measurements with numerical simulations, demonstrate switching between two stable degenerate target Skyrmion ground states that have opposite polarities and rotation senses, and discuss the observed switching mechanism.

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4 comments

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Sonhouse
5 / 5 (1) Nov 16, 2017
"as small as 200 millitesla' is not exacly a small magnetic field, 2000 gauss. I would LOVE to have 2000 gauss field magnets on my sputtering machines, which only clock in at aroud 1500 gauss.
24volts
5 / 5 (1) Nov 16, 2017
Very interesting. Still has a long way to go though before it could be used for actual memory chips.
Da Schneib
not rated yet Nov 16, 2017
@Sonhouse I'd like to know what they think they can do to make a mag field that strong that won'e affect adjacent cells stochastically.
axemaster
5 / 5 (1) Nov 17, 2017
Some of my friends at MIT DMSE are working on closely related skyrmion research. I actually designed a bunch of the equipment they are using (avalanche pulse generators, optical amplifiers). It's so interesting to be able to control the spin domains, move them around at will, watch them get stuck on pinning sites... cool stuff!

I just realized I should clarify - yes you can observe spin domains using widefield cameras! When light bounces off the surface of even a highly conductive material, the fields actually penetrate a little into the volume, where their polarization angle can be slightly rotated. Using a pair of polarizers and a good camera you can actually see the spin domains.

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