Scientists from the RIKEN Center for Emergent Matter Science and collaborators have shown that they can manipulate single skyrmions-tiny magnetic vortices that could be used as computing bits in future ultra-dense information storage devices-using pulses of electric current, at room temperature.
Skyrmions-tiny particles that can be moved under small electric currents several orders lower than those used for driving magnetic domain walls-are being studied in the hope of developing promising applications in storage devices with low energy consumption. The key to creating spintronics devices is the ability to effectively manipulate, and measure, a single tiny vortex.
Most research to date has focused on the dynamics for skyrmions a micrometer or more in size or skyrmion clusters stabilized below room temperature. For the current research, published in Nature Communications, the researchers used a thin magnetic plate made up of a compound of cobalt, zinc, and manganese, Co9Zn9Mn2, which is known as a chiral-lattice magnet. They directly observed the dynamics of a single skyrmion, with a size of 100 nanometers, at room temperature using Lorentz transmission electron microscopy. They were able to track the motions of the skyrmion and control its Hall motion directions by flipping the magnetic field, when they subjected it to ultrafast pulses of electric current – on the scale of nanoseconds. The group found that the skyrmion’s motion demonstrated a dynamic transition from a pinned static state to a flow motion by way of creep motion under the stimulus of electric current, and quantified the relatively fast velocity of the skyrmion, over 3m per second.
According to first author Licong Peng, special postdoctoral researcher, RIKEN CEMS, “This is very exciting, because for the first time, we have been able to use electrical currents to manipulate single skyrmions at room temperature in chiral-lattice magnets.“
According to Xiuzhen Yu, leader, research group, “This research will lead to further studies of dynamics of various topological spin textures, leading to the development of skyrmion-based devices.“
Article: Dynamic transition of current-driven single-skyrmion motion in a room-temperature chiral-lattice magnet
Nature Communications has published an article written by Licong Peng, Kosuke Karube, Yasujiro Taguchi, RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan, Naoto Nagaosa, RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan, and Department of Applied Physics, University of Tokyo, Bunkyo-ku, Japan, Yoshinori Tokura, RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan, Department of Applied Physics, University of Tokyo, Bunkyo-ku, Japan, and Tokyo College, University of Tokyo, Bunkyo-ku, Japan, and Xiuzhen Yu, RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan.
Fig. 1: A single skyrmion in a Co9Zn9Mn2-based microdevice at room temperature (RT).
a Schematic of the crystal structure of Co9Zn9Mn2 (space group: P4132 or P4332). b The cross-section drawing of the microdevice consisting of a (001) Co9Zn9Mn2 thin plate (see details in Supplementary Fig. 1). c Magnetic induction maps of a metastable skyrmion generated at RT and a magnetic field of −80 mT applied along the –z-direction. The inset in (c) shows the over-focus L-TEM image of the skyrmion. The color wheel encodes the direction of in-plane magnetic components, and dark contrast encodes the out-of-plane components. d Schematic of skyrmion motion with the translational displacement (△x) and transverse displacement (△y) induced by pulsed electric current (j) flowing from left to right.
Abstract: “Driving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Recently progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Here, we report the motion tracking and control of a single skyrmion at room temperature in the chiral-lattice magnet Co9Zn9Mn2 using nanosecond current pulses. We have directly observed that the skyrmion Hall motion reverses its direction upon the reversal of skyrmion topological number using Lorentz transmission electron microscopy. Systematic measurements of the single-skyrmion trace as a function of electric current reveal a dynamic transition from the static pinned state to the linear flow motion via a creep event, in agreement with the theoretical prediction. We have clarified the role of skyrmion pinning and evaluated the intrinsic skyrmion Hall angle and the skyrmion velocity in the course of the dynamic transition. Our results pave a way to skyrmion applications in spintronic devices.“