By Xichao ZHANG  (Research assistant of Prof. Zhou Yan’s group)

Magnetic skyrmions are particle-like topological spin configurations that usually exist in magnets with chiral exchange interactions. They are expected to be essential components of future spintronic devices due to their promising nature of providing ultra-low energy consumption. An important fundamental property of skyrmions is that they are predicted to have Hall effect when driving by electric currents, however, the experimental observation of skyrmion Hall effect has remained elusive.

A CUHK(SZ) researcher is part of an international team that have demonstrated the direct experimental observation of skyrmion Hall effect in magnetic films. The physicists revealed a strong similarity between the conventional charge Hall effect and the skyrmion Hall effect. The observation of skyrmion Hall effect may potentially create many exciting opportunities, such as topological selection. Their results have been published in advance online on 19 September in the most prestigious journal in physics --- Nature Physics (doi:10.1038/nphys3883). The first author of the paper is Dr. Wanjun Jiang from Tsinghua University. Mr. Xichao Zhang, who is a research assistant of Prof. Yan Zhou’s group at the School of Science and Engineering, is the co-first author of the paper. The main contribution of Dr. Zhou’s group is to theoretically and numerically confirm the experiments performed by the scientists from Argonne National Laboratory, USA.

Prof. Yan Zhou explained the significance of this work in a recent review. “The conventional Hall effect describes the transverse deflection of charged particles driven by electric currents in a conductor under the influence of perpendicular magnetic fields, which is a result of the well-known Lorentz force. Hence, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, exhibit similar characteristics. The magnetic skyrmion, which has a unit topological charge, serves as an excellent example to clarify such lingering issue. In this collaboration work, the international teams indeed experimentally observe the skyrmions get deflected by an applied current due to the topological charge – so called topological Hall effect (THE). The experimental observation of the skyrmion Hall effect may potentially create many exciting opportunities for the emerging field of skyrmionics.”

“The direct observation of the skyrmion Hall effect shows that the skyrmion dynamics differs from the theoretical prediction for perfectly pure materials, which implies that the dynamics of skyrmions may be strongly influenced by local impurities in the experimental systems. This work provides an in-depth understanding of skyrmion physics which could be useful for future implementation of skyrmion-based devices.” Mr. Xichao Zhang added.

This paper is one example of Prof. Yan Zhou’s recent research achievements regarding the basic physics of skyrmions as well as their potential applications. His group and his international collaborators have also achieved several significant milestones in this year. Prof. Yan Zhou’s group (with first and co-corresponding authorships) and several international and domestic collaborators published a research article in Physical Review B on 19 September (doi: 10.1103/PhysRevB.94.094420), which reports the control and manipulation of a novel magnetic skyrmionium in nanostructures.

In the forthcoming issue of Proceedings of the IEEE in October 10, 2016, one review article by Prof. Yan Zhou’s group (as the co-corresponding author) and his domestic collaborators from Beihang University (doi:10.1109/JPROC.2016.2591578) provides a comprehensive overview of the current status and outlook of skyrmions from the perspective of electronic applications.

“These results provide many fascinating physics and rich perspectives for the emerging research field of "skyrmionics", using skyrmions as information carrier in next-generation spintronic devices and circuits. Our results would impact the scientific community significantly in the near future.” Prof. Yan Zhou summarized.