Tiny magnetic vortices, so-called skyrmions, are considered promising candidates for particularly space- and energy-saving data storage. Scientists at Research Centre Jülich have now experimentally demonstrated another class of magnetic objects that also behave like particles. They could take the development of data storage a big step forward. While Skyrmions encode the binary “1”, they could represent the so far missing “0”. The flat three-dimensional structures appear on the surface of special alloys and are also referred to by researchers as “chiral magnetic bobbers”.
“For a long time, skyrmions were the only known research objects in the field of so-called chiral magnets. With the “magnetic bobbers”, we are now adding another class that has a number of unique properties,” says Nikolai Kiselev from the Peter Grünberg Institute in Jülich. Three years ago, together with other researchers, he theoretically predicted the existence of this new class of magnetic objects. Jülich specialists in the field of electron microscopy have now proved their existence experimentally for the first time.
The stability of skyrmions and these novel magnetic structures is related to a property also known as chirality. Just as the right hand cannot be converted into the left for reasons of symmetry, right-handed and left-handed magnetic vertebrae cannot be converted into one another. The structures are also very small. Their diameter is typically only a few tens of nanometers. Data can therefore be packed very tightly on a memory chip. The observation of such tiny magnetic textures is only possible with special techniques, which are only available in a few laboratories worldwide.
Chiral magnetic bobbers and skyrmions are, apart from their size, also interesting for applications for another reason. You are mobile. This distinguishes them from data bits on a hard disk. Skyrmions other so-called magnetic solitons can be shifted along a given distance on a chip by electrical impulses. This opens up completely different possibilities for the realization of magnetic solid-state memories, for example according to the concept of the so-called Skyrmion racetrack memory: With movable Skyrmions, data can move from write to read elements without the need for moving parts such as read and write heads or a rotating hard disk.
The newly discovered magnetic structures now make it possible to encode digital data directly with two different types of magnetic objects, namely with skyrmions and “magnetic bobbers”. “Until now it was assumed that the data were somehow represented as a sequence of skyrmions and blanks,” explains Stefan Blügel. In order to be able to represent the “0” as well as the “1”, a further information carrier is required in addition to the known skyrmions. This can be the distance between successive Skyrmions. In order that no information is lost through spontaneous drift movements of the skyrmions, their position would have to be limited or quantized in some way. With direct coding with two different objects, on the other hand, these can move relatively freely without having to maintain precise distances.
Further research is needed to turn the discovery into real-world products. Kiselev and his colleagues have demonstrated the novel structures in an iron-germanium alloy. They are only stable up to 200 Kelvin, which corresponds to -73.5 degrees Celsius. For theoretical reasons, however, it can be predicted that the novel vortices will also occur in other material combinations; possibly even at room temperature.