Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets

Abstract

Room-temperature skyrmions in ferromagnetic films and multilayers show promise for encoding information bits in new computing technologies. Despite recent progress, ferromagnetic order generates dipolar fields that prevent ultrasmall skyrmion sizes, and allows a transverse deflection of moving skyrmions that hinders their efficient manipulation. Antiferromagnetic skyrmions shall lift these limitations. Here we demonstrate that room-temperature antiferromagnetic skyrmions can be stabilized in synthetic antiferromagnets (SAFs), in which perpendicular magnetic anisotropy, antiferromagnetic coupling and chiral order can be adjusted concurrently. Utilizing interlayer electronic coupling to an adjacent bias layer, we demonstrate that spin-spiral states obtained in a SAF with vanishing perpendicular magnetic anisotropy can be turned into isolated antiferromagnetic skyrmions. We also provide model-based estimates of skyrmion size and stability, showing that room-temperature antiferromagnetic skyrmions below 10 nm in radius can be anticipated in further optimized SAFs. Antiferromagnetic skyrmions in SAFs may thus solve major issues associated with ferromagnetic skyrmions for low-power spintronic devices.

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Fig. 1: SAF in different configurations.
Fig. 2: Elaboration of (Pt/Co/Ru) multilayers and BL to obtain an optimized biased SAF.
Fig. 3: Room-temperature MFM observation of magnetization textures in SAFs.
Fig. 4: Quantitative analysis of MFM signal (phase offset in lift mode).
Fig. 5: Evaluation of sizes and energies of antiferromagnetic skyrmions in the BL-SAF system.

Data availability

All relevant data presented in the manuscript and in the Supplementary Information supporting the findings of this study are available from the corresponding authors upon request.

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Acknowledgements

The authors thank Y. Sassi for his participation to additional experiments included in the Supplementary Information and W. Akhtar, A. Finco, S. Chouaieb and V. Jacques for discussions about the magnetic imaging of SAFs. Financial support from the Agence Nationale de la Recherche, France, under grant agreement no. ANR-17-CE24-0025 (TOPSKY), the Horizon2020 Framework Programme of the European Commission under FET-Proactive Grant agreement no. 824123 (SKYTOP) and FET-Open grant agreement no. 665095 (MAGicSky), and the DARPA TEE programme through grant MIPR no. HR0011831554 is acknowledged.

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W.L., N.R., V.C. and A.F. conceived the project. W.L. deposited the multilayered films, with the help of S.C. and F.A. W.L. and F.A. performed the magnetic characterization of the SAFs and optimization of the magnetic properties. W.L., D.M. and F.A. performed the MFM experiments, with the help of K.B. and A.V. W.L. performed the micromagnetic simulations. W.L., N.R. and V.C. prepared the manuscript, and all authors discussed and contributed to the final manuscript.

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Correspondence to William Legrand or Vincent Cros.

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Supplementary Notes 1–12, Supplementary Figs. 1–26, Supplementary Tables 1–7 and Supplementary refs. 1–11.

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Legrand, W., Maccariello, D., Ajejas, F. et al. Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets. Nat. Mater. 19, 34–42 (2020). https://doi.org/10.1038/s41563-019-0468-3

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