Jul 04, 2016
Magnetic skyrmions observed at room temperature
Contact : Olivier Boulle

Fig. 1 In black and white : magnetic microscopy image of a magnetic skyrmion in the middle of a squared nanodot (white dashed line, approximately 400 nm wide). Colored arrows : illustration of the magnetic structure of the skyrmion.

These nanoscale magnetic textures have been observed at room temperature in materials compatible with the microelectronics industry by  O. Boulle and his colleagues from Spintec in Grenoble. These results break an important barrier for the use of skyrmions as nanoscale information carrier in our computers.

 It‘s an important breakthrough that was recently made by O. Boulle and this colleagues from Spintec and Institut Néel in Grenoble by demonstrating magnetic skyrmions stable at room temperature. These structures are currently fascinating many research groups in the world, as they offer a new way to store and process information in our computers. These nanoscale magnetic quasi-particles are composed of elementary nanomagnets that wind to form a stable spiral structure, like a well tighten node. Although predicted in the 80’s, it has only been observed for the first time in 2009. Three years later, two research teams demonstrated that skyrmions can be manipulated by very low electrical currents, which opens a path for their use as information carriers in computing devices. Several groundbreaking memory and logic devices based on the manipulation of skyrmion in nanotracks have been proposed, that promise very large   information density and low power consumption. However, these applications still remained distant so far as skyrmions had been observed only at low temperature or in the presence of   large magnetic fields and in exotic materials far from any applications.

By demonstrating skyrmions stable at room temperature and in the absence of external magnetic field, O. Boulle and his colleagues have thus broken a major barrier. To achieve this result, they deposited an ultrathin magnetic layer of cobalt (a few atom thick) in sandwich between a layer of a heavy metal (platinum) and a layer of magnesium oxide. This sandwich structure allows to strongly enhance the magnetic interaction at the origin of the spiral structure of the skyrmion, named Dzyaloshinskii-Moryia, which is present at the interface between a magnetic metal and a heavy metal. The deposition techniques used, named sputtering deposition, has the advantage of being fast and is commonly used in the microelectronics industry.

Once the material was identified, the next step was to observe the skyrmion, in particular its internal spiral structure. For this objective, a technique with high spatial resolution and high magnetic sensitivity is needed, which can be achieved using polarized synchrotron x-rays in combination with PhotoEmission Electron microscopes (PEEM). Images of magnetic skyrmions taken with such “XMCD-PEEM” magnetic microscopes, taken at  the Elettra synchrotron in Trieste, Italy, are shown in Figure 1. The next step will be to move these skyrmions using electrical current, a move further toward the use of these particles to code and manipulate the information at the nanoscale in computing devices.

These results were obtained through a collaboration between several French laboratories : Spintec and Institut Néel in Grenoble, the laboratory of process and material sciences, Paris 13 University. The XMCD-PEEM  magnetic imaging experiments were carried out in Alba synchrotron in Barcelona, Spain, and in Elettra synchrotron in Trieste, Italy. Samples have been fabricated on the nanofabrication plateform PTA in Grenoble, France.

More reading :

  • « Room-temperature chiral magnetic skyrmions in ultrathin magnetic nanostructures » O. Boulle et al., Nature Nanotechnology (2016), http://dx.doi.org/10.1038/nnano.2015.315
  • « Skyrmion on the tracks », A. Fert et al., Nature Nanotechnology, 8, 152 (2016)
  • « Le skyrmion, mémoire en attente» D.Larousserie, Le monde, 26/08/2013

 

 

 

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