Manipulating tiny skyrmions with small electric currents

Date:
June 17, 2020
Source:
RIKEN
Summary:
A research group has managed to manipulate and track the movement
of individual magnetic vortices called skyrmions, which have been
touted as strong candidates to act as information carriers in
next-generation storage devices and as synapses for neuromorphic
computing.



FULL STORY ==========================================================================
A research group from the RIKEN Center for Emergent Matter Science have
managed to manipulate and track the movement of individual magnetic
vortices called skyrmions, which have been touted as strong candidates
to act as information carriers in next-generation storage devices and as synapses for neuromorphic computing, They were able to move and measure skyrmions of 80 nanometers in size, using a small electric current a
thousand times weaker than those used for drives of magnetic domain
walls in the racetrack memory.


==========================================================================
This work could be key to the creation of a new type of device called "skyrmion-based racetrack" memory, , which uses topological electron-spin textures, allowing much greater energy efficiency that conventional
electronic devices. Essentially, this type of memory involves using
currents of spin- aligned electricity to put a magnetic domain past
magnetic "read/write heads" - - information carriers which act as
either ones or zeroes. In the case of skyrmions, the existence and non-existence of a skyrmion can serve as a bit of information. What has
proven difficult, however, is in effectively measuring skyrmions without
using high currents of electricity.

In the current work, published in Science Advances, the group, led by
Xiuzhen Yu of the RIKEN Center for Emergent Matter Science, set out
working with a thin film of iron germanide, a type of material known as
a helimagnet, making it easier to manipulate the small magnetic vortices
called skyrmions. Importantly, the film used for the study was developed
with a notch, which allowed the spin current to be localized in a specific
area near the corner of the notch.

Normally, skyrmions emerge as part of a structure called a skyrmion
crystal, which incorporates a number of vortices and hence is quite
difficult to move.

An important goal of research has been to isolate and manipulate
individual skyrmions, making it easier to move them, but this is a tricky process. By experimenting with the directional currents, and recording
the results with sequential Lorentz transmission electron microscopy,
the group found a point where they could isolate individual skyrmions,
and record how they moved based on known processes such as the topological
Hall effect.

According to Xiuzhen Yu, who led the research group, "Through this work we
have demonstrated that it is possible to manipulate and track individual skyrmions and its crystal using a relatively low electric current, and
we hope that this will help the development of more energy efficient
racetrack memory as well as neuromorphic computing. We realize that
there are limitations in terms of how much the skyrmions can be moved,
and plan to work, by developing a bilayer system that can host combined skyrmions, to further improve the device to enable it to be put into
practical application."

========================================================================== Story Source: Materials provided by RIKEN. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Yu at al. Motion tracking of 80-nm-size skyrmions upon directional
current injections. Sci. Adv., 2020 DOI: 10.1126/sciadvaaz9744 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200617150034.htm

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