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Long-range chiral exchange interaction in synthetic antiferromagnets


The exchange interaction governs static and dynamic magnetism. This fundamental interaction comes in two flavours—symmetric and antisymmetric. The symmetric interaction leads to ferro- and antiferromagnetism, and the antisymmetric interaction has attracted significant interest owing to its major role in promoting topologically non-trivial spin textures that promise fast, energy-efficient devices. So far, the antisymmetric exchange interaction has been found to be rather short ranged and limited to a single magnetic layer. Here we report a long-range antisymmetric interlayer exchange interaction in perpendicularly magnetized synthetic antiferromagnets with parallel and antiparallel magnetization alignments. Asymmetric hysteresis loops under an in-plane field reveal a unidirectional and chiral nature of this interaction, which results in canted magnetic structures. We explain our results by considering spin–orbit coupling combined with reduced symmetry in multilayers. Our discovery of a long-range chiral interaction provides an additional handle to engineer magnetic structures and could enable three-dimensional topological structures.

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The data sets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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We acknowledge insightful discussions with M. Hoffmann, S. Blügel, B. Dupé and S.-B. Choe. We acknowledge F. Ummelen for personal discussions on her results that are relevant to this work. D.-S.H., K.L. and M.K. acknowledge support from MaHoJeRo (DAAD Spintronics network, project number 57334897) and the German Research Foundation (in particular SFB TRR 173 Spin+X). K.L. acknowledges the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement Standard EF no. 709151. M.-H.J. acknowledges support from the National Research Foundation (NRF) of Korea grant funded by the Korea government (MEST) (nos 2017R1A2B3007918 and 2016M3A7B4910400). C.-Y.Y. acknowledges support from the NRF of South Korea under Grant 2017R1A2B3002621 and 2015M3D1A1070465, and J.-P.H. and Y.M. acknowledge computing time on the supercomputers JUQUEEN and JURECA at the Jülich Super-computing Center, and at the JARA-HPC cluster of RWTH Aachen, as well as funding under the SPP 2137 “Skyrmionics” (project MO 1731/7-1) and project MO 1731/5-1 of the Deutsche Forschungsgemeinschaft (DFG). D.-S.H. and K.-W.K. were supported by the Korea Institute of Science and Technology (KIST) institutional program (no. 2E29410) and a National Research Council of Science & Technology (NST) grant (no. CAP-16-01-KIST) funded by the Korea government (Ministry of Science and ICT). K.-W.K. acknowledges the DFG (no. SI 1720/2-1).

Author information

M.-H.J. and D.-S.H. conceived the original idea. D.-S.H., K.L., M.-H.J. and M.K. planned and designed the experiments. D.-S.H. and Y.V.H. fabricated the samples with R.L. and H.J.M.S. D.-S.H. and K.L. performed transport measurements with W.Y. and data analysis under the supervision of M.K. and M.-H.J. T.-W.K. provided [Pt/CoSiB]2/Pt multilayers. J.-P.H. and Y.M. performed the first-principles calculations and the analysis of relevant data. K.-W.K. provided theoretical explanations in Supplementary Information. D.-S.H. and C.-Y.Y. performed the numerical calculation based on a macrospin model. D.-S.H. wrote the paper with K.L., J.H. and M.K. All the authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Correspondence to Myung-Hwa Jung or Mathias Kläui.

Supplementary information

Supplementary Information

Supplementary Notes 1–5, Supplementary Figs. 1–9 and Supplementary references 1–13.

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Further reading

Fig. 1: Antisymmetric IEI in synthetic AFMs.
Fig. 2: Chiral and unidirectional magnetization switching behaviours.
Fig. 3: In-plane field dependence of magnetization switching fields.
Fig. 4: Effective symmetry breaking in sputtered samples and antisymmetric IEI from first principles.