Unconventional skyrmions in synthetic antiferromagnets
Source abstract
Abstract
Abstract Magnetic skyrmions are topologically protected spin textures that can act as reconfigurable nanoscale information carriers. In synthetic antiferromagnets, interlayer exchange coupling provides a control parameter beyond the interfacial Dzyaloshinskii–Moriya interaction and magnetic anisotropy. Here we engineer a synthetic antiferromagnet of two chemically distinct ferromagnets, CoB and CoFeB, in which the external field and interlayer exchange act asymmetrically on the sublattices. Their competition, acting as an effective field, gives rise to two skyrmion families in different field regimes: conventional-polarity skyrmions at large fields, and inverse-polarity skyrmions at smaller fields, where the effective field reverses sign. Using element-resolved X-ray magnetometry, correlative magnetic force and Lorentz transmission electron microscopies, and micromagnetic modelling, we show that all textures reside solely in the CoFeB layers, driven by a Ruderman–Kittel–Kasuya–Yosida exchange field from the CoB layers. This effective-field route enables programmable three-dimensional spin textures with layer-selected polarity for skyrmion-based computing.
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Research context
OpenAlex topics: Magnetic properties of thin films · Multiferroics and related materials · Advanced Condensed Matter Physics
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References (68)
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1. Nagaosa, N. & Tokura, Y. Topological properties and dynamics of magnetic skyrmions. Nat. Nanotechnol. 8, 899–911 (2013).10.1038/nnano.2013.243 ↗
2. Fert, A., Reyren, N. & Cros, V. Magnetic skyrmions: advances in physics and potential applications. Nat. Rev. Mater. 2, 17031 (2017).10.1038/natrevmats.2017.31 ↗
3. Marrows, C. H. & Zeissler, K. Perspective on skyrmion spintronics. Appl. Phys. Lett. 119, 250502 (2021).10.1063/5.0072735 ↗
4. Zázvorka, J. et al. Thermal skyrmion diffusion used in a reshuffler device. Nat. Nanotechnol. 14, 658–661 (2019).10.1038/s41565-019-0436-8 ↗
5. Finocchio, G. et al. Roadmap for unconventional computing with nanotechnology. Nano Futures 8, 012001 (2024).10.1088/2399-1984/ad299a ↗
6. Bourianoff, G., Pinna, D., Sitte, M. & Everschor-Sitte, K. Potential implementation of reservoir computing models based on magnetic skyrmions. AIP Adv. 8, 055602 (2018).10.1063/1.5006918 ↗
7. Song, K. M. et al. Skyrmion-based artificial synapses for neuromorphic computing. Nat. Electron. 3, 148–155 (2020).10.1038/s41928-020-0385-0 ↗
8. Yokouchi, T. et al. Pattern recognition with neuromorphic computing using magnetic field-induced dynamics of skyrmions. Sci. Adv. 8, abq5652 (2022).10.1126/sciadv.abq5652 ↗
9. Raab, K. et al. Brownian reservoir computing realized using geometrically confined skyrmion dynamics. Nat. Commun. 13, 6982 (2022).10.1038/s41467-022-34309-2 ↗
10. Sun, Y. et al. Experimental demonstration of a skyrmion-enhanced strain-mediated physical reservoir computing system. Nat. Commun. 14, 3434 (2023).10.1038/s41467-023-39207-9 ↗
11. Beneke, G. et al. Gesture recognition with brownian reservoir computing using geometrically confined skyrmion dynamics. Nat. Commun. 15, 8103 (2024).10.1038/s41467-024-52345-y ↗
12. Mühlbauer, S. et al. Skyrmion lattice in a chiral magnet. Science 323, 915–919 (2009).10.1126/science.1166767 ↗
13. Chen, G., Mascaraque, A., N’Diaye, A. T. & Schmid, A. K. Room temperature skyrmion ground state stabilized through interlayer exchange coupling. Appl. Phys. Lett. 106, 242404 (2015).10.1063/1.4922726 ↗
14. Jiang, W. et al. Blowing magnetic skyrmion bubbles. Science 349, 283–286 (2015).10.1126/science.aaa1442 ↗
15. Woo, S. et al. Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets. Nat. Mater. 15, 501–506 (2016).10.1038/nmat4593 ↗
16. Boulle, O. et al. Room-temperature chiral magnetic skyrmions in ultrathin magnetic nanostructures. Nat. Nanotechnol. 11, 449–454 (2016).10.1038/nnano.2015.315 ↗
17. Legrand, W. et al. Room-temperature current-induced generation and motion of sub-100 nm skyrmions. Nano Lett. 17, 2703–2712 (2017).10.1021/acs.nanolett.7b00649 ↗
18. Soumyanarayanan, A. et al. Tunable room-temperature magnetic skyrmions in Ir/Fe/Co/Pt multilayers. Nat. Mater. 16, 898–904 (2017).10.1038/nmat4934 ↗
19. Legrand, W. et al. Hybrid chiral domain walls and skyrmions in magnetic multilayers. Sci. Adv. 4, aat0415 (2018).10.1126/sciadv.aat0415 ↗
20. Duong, N. K. et al. Magnetization reversal signatures of hybrid and pure Néel skyrmions in thin film multilayers. APL Mater. 8, 111112 (2020).10.1063/5.0022033 ↗
21. Raftrey, D. et al. Quantifying the topology of magnetic skyrmions in three dimensions. Sci. Adv. 10, eadp8615 (2024).10.1126/sciadv.adp8615 ↗
22. Xu, T. et al. Imaging the spin chirality of ferrimagnetic Néel skyrmions stabilized on topological antiferromagnetic Mn3Sn. Phys. Rev. Mater. 5, 084406 (2021).10.1103/PhysRevMaterials.5.084406 ↗
23. Mandru, A.-O. et al. Coexistence of distinct skyrmion phases observed in hybrid ferromagnetic/ferrimagnetic multilayers. Nat. Commun. 11, 6365 (2020).10.1038/s41467-020-20025-2 ↗
24. Grelier, M. et al. Three-dimensional skyrmionic cocoons in magnetic multilayers. Nat. Commun. 13, 6843 (2022).10.1038/s41467-022-34370-x ↗
25. Kent, N. et al. Creation and observation of Hopfions in magnetic multilayer systems. Nat. Commun. 12, 1562 (2021).10.1038/s41467-021-21846-5 ↗
26. Duine, R. A., Lee, K.-J., Parkin, S. S. P. & Stiles, M. D. Synthetic antiferromagnetic spintronics. Nat. Phys. 14, 217–219 (2018).10.1038/s41567-018-0050-y ↗
27. Parkin, S. S. P. Systematic variation of the strength and oscillation period of indirect magnetic exchange coupling through the 3d, 4d, and 5d transition metals. Phys. Rev. Lett. 67, 3598 (1991).10.1103/PhysRevLett.67.3598 ↗
28. Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472 (1988).10.1103/PhysRevLett.61.2472 ↗
29. Bandiera, S. et al. Comparison of synthetic antiferromagnets and hard ferromagnets as reference layer in magnetic tunnel junctions with perpendicular magnetic anisotropy. IEEE Magn. Lett. 1, 3000204 (2010).10.1109/LMAG.2010.2052238 ↗
30. Hellwig, O., Maat, S., Kortright, J. B. & Fullerton, E. E. Magnetic reversal of perpendicularly-biased Co/Pt multilayers. Phys. Rev. B 65, 144418 (2002).10.1103/PhysRevB.65.144418 ↗
31. Hellwig, O., Kirk, T. L., Kortright, J. B., Berger, A. & Fullerton, E. E. A new phase diagram for layered antiferromagnetic films. Nat. Mater. 2, 112–116 (2003).10.1038/nmat806 ↗
32. Hauet, T. et al. Field driven ferromagnetic phase nucleation and propagation in antiferromagnetically coupled multilayer films with perpendicular anisotropy. Appl. Phys. Lett. 93, 042505 (2008).10.1063/1.2961001 ↗
33. Barker, C. E. A. et al. Phase coexistence and transitions between antiferromagnetic and ferromagnetic states in a synthetic antiferromagnet. Phys. Rev. B 109, 134437 (2024).10.1103/PhysRevB.109.134437 ↗
34. Legrand, W. et al. Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets. Nat. Mater. 19, 34–42 (2020).10.1038/s41563-019-0468-3 ↗
35. Darwin, E. et al. Antiferromagnetic interlayer exchange coupled Co68B32/Ir/Pt multilayers. Sci. Rep. 14, 95 (2024).10.1038/s41598-023-49976-4 ↗
36. Dohi, T., DuttaGupta, S., Fukami, S. & Ohno, H. Formation and current-induced motion of synthetic antiferromagnetic skyrmion bubbles. Nat. Commun. 10, 5153 (2019).10.1038/s41467-019-13182-6 ↗
37. Juge, R. et al. Skyrmions in synthetic antiferromagnets and their nucleation via electrical current and ultra-fast laser illumination. Nat. Commun. 13, 4807 (2022).10.1038/s41467-022-32525-4 ↗
38. Pham, V. T. et al. Fast current-induced skyrmion motion in synthetic antiferromagnets. Science 384, 307–312 (2024).10.1126/science.add5751 ↗
39. Dohi, T. et al. Observation of a non-reciprocal skyrmion hall effect of hybrid chiral skyrmion tubes in synthetic antiferromagnetic multilayers. Nat. Commun. 16, 8285 (2025).10.1038/s41467-025-63759-7 ↗
40. Büttner, F., Lemesh, I. & Beach, G. S. D. Theory of isolated magnetic skyrmions: From fundamentals to room temperature applications. Sci. Rep. 8, 4464 (2018).10.1038/s41598-018-22242-8 ↗
41. Zhang, X., Zhou, Y. & Ezawa, M. Magnetic bilayer-skyrmions without skyrmion Hall effect. Nat. Commun. 7, 10293 (2016).10.1038/ncomms10293 ↗
42. Tomasello, R. et al. Performance of synthetic antiferromagnetic racetrack memory: domain wall versus skyrmion. J. Phys. D 50, 325302 (2017).10.1088/1361-6463/aa7a98 ↗
43. Krajnak, M., McGrouther, D., Maneuski, D., O’Shea, V. & McVitie, S. Pixelated detectors and improved efficiency for magnetic imaging in stem differential phase contrast. Ultramicroscopy 165, 42–50 (2016).10.1016/j.ultramic.2016.03.006 ↗
44. Benitez, M. J. et al. Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer. Nat. Commun. 6, 8957 (2015).10.1038/ncomms9957 ↗
45. Fallon, K. et al. Quantitative imaging of hybrid chiral spin textures in magnetic multilayer systems by Lorentz microscopy. Phys. Rev. B 100, 214431 (2019).10.1103/PhysRevB.100.214431 ↗
46. Fallon, K. et al. Controlled individual skyrmion nucleation at artificial defects formed by ion irradiation. Small 16, 1907450 (2020).10.1002/smll.201907450 ↗
47. McVitie, S. et al. A transmission electron microscope study of Néel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction. Sci. Rep. 8, 5703 (2018).10.1038/s41598-018-23799-0 ↗
48. Baćani, M., Marioni, M. A., Schwenk, J. & Hug, H. J. How to measure the local Dzyaloshinskii–Moriya interaction in skyrmion thin-film multilayers. Sci. Rep. 9, 3114 (2019).10.1038/s41598-019-39501-x ↗
49. Katzgraber, H. G. & Zimanyi, G. T. Hysteretic memory effects in disordered magnets. Phys. Rev. B 74, 020405(R) (2006).10.1103/PhysRevB.74.020405 ↗
50. Raju, M. et al. The evolution of skyrmions in Ir/Fe/Co/Pt multilayers and their topological hall signature. Nat. Commun. 10, 696 (2019).10.1038/s41467-018-08041-9 ↗
51. Glavic, A. & Björck, M. GenX 3: the latest generation of an established tool. J. Appl. Crystallogr. 55, 1063–1071 (2022).10.1107/S1600576722006653 ↗
52. Scharfstein, G. A., Arbelaez, D. & Jung, J.-Y. An endstation with cryogenic coils contributing to a 0.5 tesla field and 30–400 K sample thermal control. In Proc. 9th Mechanical Engineering Design of Synchrotron Radiation Equipment and Instrumentation Conference (ed. Schaa, V. R. W.) Vol. 1, 396 (JACoW, 2016).
53. Feng, Y. et al. Magnetic force microscopy contrast formation and field sensitivity. J. Magn. Magn.Mater. 551, 169073 (2022).10.1016/j.jmmm.2022.169073 ↗
54. Zhao, X. et al. Magnetic force microscopy with frequency-modulated capacitive tip–sample distance control. New J. Phys. 20, 013018 (2018).10.1088/1367-2630/aa9ca9 ↗
55. Pandey, N., Li, M., Graef, M. D. & Sokalski, V. Stabilization of coupled Dzyaloshinskii domain walls in fully compensated synthetic anti-ferromagnets. AIP Adv. 10, 015233 (2020).10.1063/1.5130411 ↗
56. Jiang, W. et al. Quantifying chiral exchange interaction for Néel-type skyrmions via Lorentz transmission electron microscopy. Phys. Rev. B 99, 104402 (2019).10.1103/PhysRevB.99.104402 ↗
57. McVitie, S. et al. Aberration corrected Lorentz scanning transmission electron microscopy. Ultramicroscopy 152, 57–62 (2015).10.1016/j.ultramic.2015.01.003 ↗
58. Krajnak, M. Pixelated dpc. GitHub https://github.com/matkraj/PixelatedDPC (2025).
59. Giordano, A., Finocchio, G., Torres, L., Carpentieri, M. & Azzerboni, B. Semi-implicit integration scheme for Landau–Lifshitz–Gilbert–Slonczewski equation. J. Appl. Phys. 111, 07D112 (2012).10.1063/1.3673428 ↗
60. Raimondo, E. et al. Temperature-gradient-driven magnetic skyrmion motion. Phys. Rev. Appl. 18, 024062 (2022).10.1103/PhysRevApplied.18.024062 ↗
61. Tomasello, R. et al. A strategy for the design of skyrmion racetrack memories. Sci. Rep. 4, 6784 (2014).10.1038/srep06784 ↗
62. Mohammadi, J. B. et al. Reduced exchange interactions in magnetic tunnel junction free layers with insertion layers. ACS Appl. Electron. Mater. 1, 2025–2029 (2019).10.1021/acsaelm.9b00381 ↗
63. Guang, Y. et al. Electrical detection of magnetic skyrmions in a magnetic tunnel junction. Adv. Electron. Mater. 9, 2200570 (2023).10.1002/aelm.202200570 ↗
64. Liu, S. et al. Topological skyrmion-based spin-torque-diode effect in magnetic tunnel junctions. Adv. Electron. Mater. 11, e00130 (2025).10.1002/aelm.202500130 ↗
65. Tacchi, S. et al. Interfacial Dzyaloshinskii–Moriya interaction in Pt/CoFeB films: effect of the heavy-metal thickness. Phys. Rev. Lett. 118, 147201 (2017).10.1103/PhysRevLett.118.147201 ↗
66. Belmeguenai, M. et al. Interface Dzyaloshinskii–Moriya interaction in the interlayer antiferromagnetic-exchange coupled Pt/CoFeB/Ru/CoFeB systems. Phys. Rev. B 96, 144402 (2017).10.1103/PhysRevB.96.144402 ↗
67. Alshammari, K. et al. Scaling of Dzyaloshinskii–Moriya interaction with magnetization in Pt/Co(Fe)B/Ir multilayers. Phys. Rev. B 104, 224402 (2021).10.1103/PhysRevB.104.224402 ↗
68. Fallon, K. et al. Data associated with ‘Unconventional skyrmions in synthetic antiferromagnets’. University of Glasgow Data Repository https://doi.org/10.5525/gla.researchdata.2296 (2026).10.5525/gla.researchdata.2296 ↗