On-chip skyrmion synapse regulated by Oersted field

Magnetic skyrmions are real-space topological spin textures, which have been frequently discussed in the context of information carriers for energy-efficient and high-integration spintronic memory and computing, such as neuromorphic computing. Toward future applications in neuromorphic computing, the design of efficient and reliable on-chip skyrmion synaptic devices is a crucial requirement, which is yet to be adequately addressed. Here, we propose an on-chip skyrmion artificial synaptic device by integrating an “Ω” shaped on-chip wire with a nanodisk in the wire. By applying current pulses to the wire, the size of the skyrmion in the nanodisk could be adjusted by the generated Oersted fields. Meanwhile, the perpendicular magnetization of the nanodisk varies simultaneously, which can serve as the weight for artificial synapses. Since no current flows through the skyrmion-hosting material, current-generated local heating is avoided, and hysteresis is limited as well. As a consequence, the designed skyrmion artificial synapse allows highly linear responses. In particular, the artificial neural network based on the synapse can achieve an accuracy of more than 95% in performing the handwritten digit recognition task. This study lays a theoretical foundation for the development of highly linear skyrmion-based artificial synaptic devices, which could also be implemented for designing novel on-chip neuromorphic computing devices based on spin textures.