New shortcut enables faster creation of spin pattern in magnet

Date:
October 5, 2020
Source:
Radboud University Nijmegen
Summary:
Physicists have discovered a much faster approach to create a
pattern of spins in a magnet. This 'shortcut' opens a new chapter
in topology research. Interestingly, this discovery also offers an
additional method to achieve more efficient magnetic data storage.



FULL STORY ========================================================================== Physicists have discovered a much faster approach to create a pattern
of spins in a magnet. This 'shortcut' opens a new chapter in topology
research.

Interestingly, this discovery also offers an additional method to achieve
more efficient magnetic data storage. The research will be published on
5 October in Nature Materials.


========================================================================== Physicists previously demonstrated that laser light can create a pattern
of magnetic spins. Now they have discovered a new route that enables this
to be done much more quickly, in less than 300 picoseconds (a picosecond
is one millionth of a millionth of a second). This is much faster than
was previously thought possible.

Useful for data storage: skyrmions Magnets consist of many small
magnets, which are called spins. Normally, all the spins point in
the same direction, which determines the north and south poles of
the magnet. But the directions of the spins together sometimes form
vortex-like configurations known as skyrmions.

"These skyrmions in magnets could be used as a new type of data storage," explains Johan Mentink, physicist at Radboud University. For a number of
years, Radboud scientists have been looking for optimal ways to control magnetism with laser light and ultimately use it for more efficient data storage. In this technique, very short pulses of light are fired at a
magnetic material. This reverses the magnetic spins in the material,
which changes a bit from a 0 to a 1.

"Once the magnetic spins take the vortex-like shape of a skyrmion,
this configuration is hard to erase," says Mentink. "Moreover, these
skyrmions are only a few nanometers (one billionth of a meter) in size,
so you can store a lot of data on a very small piece of material."
Shortcut The phase transition between these two states in a magnet --
all the spins pointing in one direction to a skyrmion -- is comparable
to a road over a high mountain. The researchers have discovered that you
can take a 'shortcut' through the mountain by heating the material very
quickly with a laser pulse.

Thereby, the threshold for the phase transition becomes lower for a very
short time.

A remarkable aspect of this new approach is that the material is first
brought into a very chaotic state, in which the topology -- which
can be seen as the number of skyrmions in the material -- fluctuates
strongly. The researchers discovered this approach by combining X-rays generated by the European free electron laser in Hamburg with extremely advanced electron microscopy and spin dynamics simulations. "This research therefore involved an enormous team effort," Mentink emphasises.

New possibilities This fundamental discovery has opened a new chapter
in topology research.

Mentink expects that many more scientists will now start to look for
similar ways to 'take a shortcut through the mountain' in other materials.

This discovery also enables new approaches to create faster and
more efficient data storage. There is an increasing need for this,
for example due to the gigantic, energy-guzzling data centres that are
required for massive data storage in the cloud. Magnetic skyrmions can
provide a solution to this problem. Because they are very small and can
be created very quickly with light, a lot of information can potentially
be stored very quickly and efficiently on a small area.


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


========================================================================== Journal Reference:
1. Bu"ttner, F., Pfau, B., Bo"ttcher, M. et al. Observation of
fluctuation-
mediated picosecond nucleation of a topological phase. Nat. Mater.,
2020 DOI: 10.1038/s41563-020-00807-1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201005112131.htm

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