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Abstract: Magnetic skyrmions, spin swirling particle like entities, have been in the focal point of many research in condensed matter physics due to their solitonic nature combined with chiral and topological properties. The main challenge for their practical application is ensuring room temperature stability and high mobility without unwanted transverse deviation (skyrmion Hall effect: SkHE). Achieving thermal stability typically requires multi-layered structures, which introduce dipolar coupling and enlarge skyrmions. [1] Other challenges include energy dissipation, non-optimized spin torques, and domain wall pinning, which all hinder skyrmion mobility. A promising solution is using antiferromagnetically coupled sub-layers, such as synthetic antiferromagnets (SAFs) or synthetic ferrimagnets, which ensure reduction in skyrmion size and SkHE due to neutralized magnetization and angular momentum [2, 3].
In the present work, we have delved into both SAF and ferrimagnetic multilayers to enhance skyrmion mobility while maintaining their steadfast stability. In the first part of the presentation, I will demonstrate the innovative techniques we have employed to stabilize and manipulate skyrmions electrically in SAFs without the need for an external magnetic field. [1, 4] This simultaneously simplifies device architecture and facilitates downsizing of these devices. In the second part, I will highlight the solitonic nature of these skyrmions, focusing on their efficient electrical nucleation and motion. Finally, I will show that stable, compact skyrmions in synthetic ferrimagnets can be driven in the viscous flow regime under the influence of spin-orbit torques. [5, 6] By simultaneous control of antiferromagnetic coupling, interfacial DMI, spin-orbit torques, and domain wall pinning of the heterostructure, we could achieve the skyrmion velocity up to 400 m/s for skyrmions with diameters ~160 nm and below while moving them in a straight trajectory. [5, 6] I will conclude by outlining future research directions focused on leveraging these topological textures to bridge the gap between classical and quantum computing, highlighting their unique potential for simultaneous application in probabilistic, neuromorphic, and quantum computing paradigms.
References:
[1] S. Mallick et al, Physical Review Applied 18, 064072 (2022)
[2] S. Panigrahy, S. Mallick et al, Physical Review B 106, 144405 (2022)
[3] L. Berges, …, S. Mallick et al, Physical Review B 106, 144408 (2022)
[4] S. Mallick et al, Advanced Functional Materials 34, 2409528 (2024)
[5] S. Mallick et al, Nature Communications 15, 8472 (2024)
[6] S. Mallick et al, arXiv.2502.11621 (2025) |