Magnetic skyrmions are small swirling spin textures that can form in materials with strong Dzyaloshinskii–Moriya interactions (DMIs). The nontrivial topology of skyrmions provides stability and makes skyrmions attractive for applications [1]. Recently, antiferromagnetically (AFM)-coupled skyrmions have been of increasing interest because they are more attractive candidates for developing spin-based information storage and sensing devices with higher stability, speed, and capacity, as compared to ferromagnetic skyrmions. In this talk, I will report the discovery of a spin memory effect in skyrmions that stems from their topology [2]. We have created stable antiferromagnetically coupled bubble skyrmion pairs at room temperature in [Co/Gd/Pt]10 multilayered films that undergo a spin reorientation transition (SRT) as the temperature is decreased. Photoemission electron microscopy imaging [3] shows that these bubble skyrmions evolve into dramatically different in-plane spin textures through the SRT and reform completely on warming back up. Simulations demonstrate that DMIs play a key role in this spin memory effect and furthermore reveal that the topological charge is preserved throughout the dramatic spin texture rearrangement and recovery. The discovered spin memory effect provides a means to encrypt and recover spin information that could serve as the basis for a magnetic analog of invisible ink, and it may also inspire new approaches to controlled skyrmion formation and manipulation for logic applications.

[1] W. Jiang, X. Zhang, G. Yu, W. Zhang, X. Wang, M. Benjamin Jungfleisch, J. Pearson, X. Cheng, O. Heinonen, K. L. Wang, Y. Zhou, A. Hoffmann, and S. teVelthuis, "Direct observation of the skyrmion Hall effect," Nature Physics, vol. 13, no. 2, pp. 162-169, 2017.

[2] X. Wang, A. R. Stuart, M. S. Swyt, C. M. Q. Flores, A. T. Clark, A. Fiagbenu, R. V. Chopdekar, P. N. Lapa, Z. Xiao, D. Keavney, R. Rosenberg, M. Vogel, J. E. Pearson, S. G. E. t. Velthuis, A. Hoffmann, K. S. Buchanan, and X. M. Cheng, "Topological spin memory of antiferromagnetically coupled skyrmion pairs in multilayers," Physical Review Materials, vol. 6, no. 8, p. 084412, 2022.

[3] X. M. Cheng and D. J. Keavney, "Studies of nanomagnetism using synchrotron-based x-ray photoemission electron microscopy (X-PEEM)," Reports on Progress in Physics, vol. 75, no. 2, p. 026501, 2012.

Please contact phweb@ust.hk should you have questions about the talk.