Seonghoon Woo

In this work, we demonstrate magnetic skyrmion-based artificial synapses for neuromorphic computing and thus artificial neural network for advanced AI systems. In particular, we present that the current-induced creation, motion, detection and deletion of skyrmions at room temperature can be used to mimic the potentiation and depression behaviours of biological synapses. Using chip-level simulations, we further demonstrate that such artificial synapses based on magnetic skyrmions could be used… Show more

In this work, we demonstrate magnetic skyrmion-based artificial synapses for neuromorphic computing and thus artificial neural network for advanced AI systems. In particular, we present that the current-induced creation, motion, detection and deletion of skyrmions at room temperature can be used to mimic the potentiation and depression behaviours of biological synapses. Using chip-level simulations, we further demonstrate that such artificial synapses based on magnetic skyrmions could be used for AI tasks such as pattern recognition. This work suggest a new route towards magnetic texture-based neuromorphic computing and future AI. Show less

In this work, for the first time, we demonstrate the deterministic writing and deleting of single isolated skyrmions at room temperature. The process is driven by the application of current pulses, which induce spin–orbit torques, and is directly observed using a time-resolved nanoscale X-ray imaging technique. We provide a current pulse profile for the efficient and deterministic writing and deleting process. Using micromagnetic simulations, we also reveal the microscopic mechanism of the… Show more

In this work, for the first time, we demonstrate the deterministic writing and deleting of single isolated skyrmions at room temperature. The process is driven by the application of current pulses, which induce spin–orbit torques, and is directly observed using a time-resolved nanoscale X-ray imaging technique. We provide a current pulse profile for the efficient and deterministic writing and deleting process. Using micromagnetic simulations, we also reveal the microscopic mechanism of the topological fluctuations that occur during this process. This work has cleared a crucial hurdle toward building a practical device. Show less

In this paper, we demonstrate the stabilization of ferrimagnetic skyrmions and their current-driven dynamics in GdFeCo films. By utilizing element-specific X-ray imaging, we find that the skyrmions in the Gd and FeCo sublayers are antiferromagnetically exchange-coupled. We further confirm that ferrimagnetic skyrmions can move at a high velocity with reduced skyrmion Hall angle. Our findings described in this paper open the door to ferrimagnetic and antiferromagnetic skyrmionics while providing… Show more

In this paper, we demonstrate the stabilization of ferrimagnetic skyrmions and their current-driven dynamics in GdFeCo films. By utilizing element-specific X-ray imaging, we find that the skyrmions in the Gd and FeCo sublayers are antiferromagnetically exchange-coupled. We further confirm that ferrimagnetic skyrmions can move at a high velocity with reduced skyrmion Hall angle. Our findings described in this paper open the door to ferrimagnetic and antiferromagnetic skyrmionics while providing key experimental evidences of recent theoretical studies.
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In this publication, we report nanosecond-dynamics of a 100nm-diameter magnetic skyrmion during a current pulse application, using a time-resolved pump-probe soft X-ray imaging technique. We demonstrate that distinct dynamic excitation states of magnetic skyrmions, triggered by current-induced spin–orbit torques, can be reliably tuned by changing the magnitude of spin–orbit torques. Our findings show that the dynamics of magnetic skyrmions can be controlled by the spin–orbit torque on the… Show more

In this publication, we report nanosecond-dynamics of a 100nm-diameter magnetic skyrmion during a current pulse application, using a time-resolved pump-probe soft X-ray imaging technique. We demonstrate that distinct dynamic excitation states of magnetic skyrmions, triggered by current-induced spin–orbit torques, can be reliably tuned by changing the magnitude of spin–orbit torques. Our findings show that the dynamics of magnetic skyrmions can be controlled by the spin–orbit torque on the nanosecond time scale, which points to exciting opportunities for ultrafast and novel skyrmionic applications in the future. Show less

We show numerically and experimentally that colliding domain walls (DWs) release energetic spin wave bursts that can couple to and assist depinning of nearby DWs. Hence, DWs can be used as stationary reservoirs of exchange energy that can be efficiently generated, manipulated, and used to release SWs on demand, which can subsequently be detected again using DWs. This work highlights a route towards integrating DWs and SWs for enhanced functionality in spintronics applications.

We report the observation of stable magnetic skyrmions at room temperature in ultrathin transition metal ferromagnets with magnetic transmission soft X-ray microscopy. We also demonstrate the ability to generate stable skyrmion lattices and drive trains of individual skyrmions by short current pulses along a magnetic racetrack at speeds exceeding 100 m s−1 as required for applications. Our findings provide experimental evidence of recent predictions10, 11, 12, 13 and open the door to… Show more

We report the observation of stable magnetic skyrmions at room temperature in ultrathin transition metal ferromagnets with magnetic transmission soft X-ray microscopy. We also demonstrate the ability to generate stable skyrmion lattices and drive trains of individual skyrmions by short current pulses along a magnetic racetrack at speeds exceeding 100 m s−1 as required for applications. Our findings provide experimental evidence of recent predictions10, 11, 12, 13 and open the door to room-temperature skyrmion spintronics in robust thin-film heterostructures. Show less