Skyrmion bubbles are stable at room temperature and a zero magnetic field

When stable in a zero magnetic field and room temperature, magnetic skyrmions – topologically protected patterns of electron spins – show potential for applications in spintronics memory or logic devices. Although stabilizing skyrmion formations can be accomplished by applying a small magnetic field from the maze domain ground state, this is often inefficient and difficult to incorporate into electronic circuits.

Nozaki et al. overcame this dilemma by studying change in the magnetization process in a Pt/Co/Ru/MgO system by changing the cobalt and ruthenium thickness.

Their goal was to create skyrmion bubbles that were stable at room temperature in a zero magnetic field. Once generated under a magnetic field and within a certain Co and Ru thickness region, their experiment showed the skyrmion bubbles remained stable when the field was removed.

“We demonstrated that skyrmion bubbles can be stabilized even from a single domain ground state, not maze domain ground state, with help of some fluctuations. We believe these results are significant, because it broadens the choice of materials and contributes to the further development of the field,” said author Tomohiro Nozaki.

The authors made a guideline to demonstrate how to create a multilayer film that could create skyrmion bubbles that are stable in these conditions and suitable for practical spintronics applications.

“There is much more to research. To apply to probabilistic computing, it is necessary to develop a structure that enhances Brownian motion of skyrmion bubbles and to realize its control with a voltage or a small current,” said Nozaki. “If we can find a way to stochastically increase the number of skyrmion bubbles by using a current instead of a magnetic field, applicability to analog devices becomes visible.”

Source: “Control of the magnetic domain of Pt/Co/Ru/MgO multilayer: Effect of Co thickness and Ru insertion,” by Tomohiro Nozaki, Makoto Konoto, Takayuki Nozaki, Hitoshi Kubota, Akio Fukushima, and Shinji Yuasa, AIP Advances (2020). The article can be accessed at https://doi.org/10.1063/1.5136044 .