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Magnetism and spin

Magnetism and spin

Skyrmion bags point the way to high-density data storage

17 Apr 2019
Picture of a skyrmion bag
The three vortex-like lumps are single skyrmions inside a skyrmion bag (Courtesy: University of Birmingham)

Skyrmions that spin on the surface of magnetic films like tiny vortices have been touted as the answer to our rising demand for data storage. Now, physicists in the UK and the US have shown that multiple anti-skyrmions can be contained within a larger structure that they have called a “skyrmion bag”, which, they say, could store more information than is possible with a single skyrmion.

“We need new technological approaches to increase the amount of data we want to store in our computers, phones and other devices, and skyrmion bags might be a route to this,” says lead author Mark Dennis of the University of Birmingham in the UK. “Rather than using trains of single skyrmions to encode binary bits, each skyrmion bag can hold any number of skyrmions, massively increasing the potential for data storage.”

Skyrmions, originally proposed as a theoretical model of the nucleon by Tony Skyrme in 1962, are particle-like excitations on the surface of magnetic films that behave like nanometre-sized magnetic vortices. They have been widely studied in many condensed matter systems, including chiral magnets and liquid crystals, and have found to be topologically similar to many other physical phenomena, and also robust against destabilizing forces. Since skyrmions are both orderly and reconfigurable, they are ideal for storing and transferring large amounts of data, and would also use far less power than conventional computer drives.

Several studies have now attempted to use skyrmions to store data, but so far only single bits have been encoded onto them. In their research, Dennis’ team aimed to improve these capabilities by creating stable, high-degree structures that can contain configurations of many anti-skyrmions within a single, larger skyrmion. Any number of anti-skyrmions can fit inside one of these so-called skyrmion bags, which suggests that they could be used to store far more information than conventional skyrmions.

Testing the properties of skyrmion bags

Dennis and colleagues demonstrated the data storage capabilities of skyrmion bags through both experiments and numerical simulations of these structures in liquid crystals. Using laser tweezers, the physicists experimentally probed pair interactions between skyrmion bags and regular skyrmions within the materials. In these interactions, the bags behaved just like single skyrmions, which suggest that the bags would be suitable for use in high-density data storage.

The physicists also proved that skyrmion bags are robust against destabilising forces – just like single skyrmions. Small-scale simulations of skyrmion bags within ferromagnets, both with and without the influence of demagnetizing magnetic fields,  confirmed that the bags maintained their high-degree configurations throughout the simulation.

Dennis’ team believe that these tests demonstrate for the first time that the diverse configurations of multiple anti-skyrmions characteristic of skyrmion bags can indeed be exploited to store and transfer data. Furthermore, they believe that their results could allow for new advances in other technologies, including display screens, sensors, and solar cells.

The research is described in Nature Physics.

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