Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet

Abstract

The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7. These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Device structure.
Fig. 2: Superconducting characterization.
Fig. 3: Flux quantization effects.
Fig. 4: The a.c. Josephson effect.

Similar content being viewed by others

Data availability

The data used in this paper are available from the authors upon reasonable request.

References

  1. Buzdin, A. I. Proximity effects in superconductor-ferromagnet heterostructures. Rev. Mod. Phys. 77, 935–976 (2005).

    Article  CAS  Google Scholar 

  2. Stolyarov, V. S. et al. Domain Meissner state and spontaneous vortex-antivortex generation in the ferromagnetic superconductor EuFe2(As0.79P0.21)2. Sci. Adv. 4, eaat1061 (2018).

    Article  Google Scholar 

  3. Aoki, D. & Flouquet, J. Ferromagnetism and superconductivity in uranium compounds. J. Phys. Soc. Jpn 81, 011003 (2012).

    Article  Google Scholar 

  4. Bergeret, F. S., Volkov, A. F. & Efetov, K. B. Long-range proximity effects in superconductor-ferromagnet structures. Phys. Rev. Lett. 86, 4096–4099 (2001).

    Article  CAS  Google Scholar 

  5. Eschrig, M., Kopu, J., Cuevas, J. C. & Schön, G. Theory of half-metal/superconductor heterostructures. Phys. Rev. Lett. 90, 137003 (2003).

    Article  CAS  Google Scholar 

  6. Houzet, M. & Buzdin, A. Long range triplet Josephson effect through a ferromagnetic trilayer. Phys. Rev. B 76, 060504 (2007).

    Article  Google Scholar 

  7. Asano, Y., Sawa, Y., Tanaka, Y. & Golubov, A. A. Odd-frequency pairs and Josephson current through a strong ferromagnet. Phys. Rev. B 76, 224525 (2007).

    Article  Google Scholar 

  8. Sperstad, I. B., Linder, J. & Sudbø, A. Josephson current in diffusive multilayer superconductor/ferromagnet/ superconductor junctions. Phys. Rev. B 78, 104509 (2008).

    Article  Google Scholar 

  9. Halterman, K., Valls, O. T. & Barsic, P. H. Induced triplet pairing in clean s-wave superconductor/ferromagnet layered structures. Phys. Rev. B 77, 174511 (2008).

    Article  Google Scholar 

  10. Eschrig, M. & Löfwander, T. Triplet supercurrents in clean and disordered half-metallic ferromagnets. Nat. Phys. 4, 138–143 (2008).

    Article  CAS  Google Scholar 

  11. Keizer, R. S. et al. A spin triplet supercurrent through the half-metallic ferromagnet CrO2. Nature 439, 825–827 (2006).

    Article  CAS  Google Scholar 

  12. Khaire, T. S., Khasawneh, M. A., Pratt, W. P. & Birge, N. O. Observation of spin-triplet superconductivity in Co-based Josephson junctions. Phys. Rev. Lett. 104, 137002 (2010).

    Article  Google Scholar 

  13. Anwar, M. S., Czeschka, F., Hesselberth, M., Porcu, M. & Aarts, J. Long-range supercurrents through half-metallic ferromagnetic CrO2. Phys. Rev. B 82, 100501 (2010).

    Article  Google Scholar 

  14. Robinson, J. W. A., Witt, J. D. S. & Blamire, M. G. Controlled injection of spin-triplet supercurrents into a strong ferromagnet. Science 329, 59–61 (2010).

    Article  CAS  Google Scholar 

  15. Sefrioui, Z. et al. Ferromagnetic/superconducting proximity effect in La0.7Ca0.3MnO3/YBa2Cu3O7−δ superlattices. Phys. Rev. B 67, 214511 (2003).

    Article  Google Scholar 

  16. Dybko, K. et al. Possible spin-triplet superconducting phase in the La0.7Sr0.3MnO3/YBa2Cu3O7/La0.7Sr0.3MnO3 trilayer. Phys. Rev. B 80, 144504 (2009).

    Article  Google Scholar 

  17. Visani, C. et al. Equal-spin Andreev reflection and long-range coherent transport in high-temperature superconductor/half-metallic ferromagnet junctions. Nat. Phys. 8, 539–543 (2012).

    Article  CAS  Google Scholar 

  18. Kalcheim, Y., Millo, O., Egilmez, M., Robinson, J. W. A. & Blamire, M. G. Evidence for anisotropic triplet superconductor order parameter in half-metallic ferromagnetic La0.7Ca0.3Mn3O proximity coupled to superconducting Pr1.85Ce0.15CuO4. Phys. Rev. B 85, 104504 (2012).

    Article  Google Scholar 

  19. Egilmez, M. et al. Supercurrents in half-metallic ferromagnetic La0.7Ca0.3MnO3. EPL 106, 37003 (2014).

    Article  Google Scholar 

  20. Crouzy, B., Tollis, S. & Ivanov, D. A. Josephson current in a superconductor-ferromagnet-superconductor junction with in-plane ferromagnetic domains. Phys. Rev. B 76, 134502 (2007).

    Article  Google Scholar 

  21. Buzdin, A. I., Mel’nikov, A. S. & Pugach, N. G. Domain walls and long-range triplet correlations in SFS Josephson junctions. Phys. Rev. B 83, 144515 (2011).

    Article  Google Scholar 

  22. Bergeret, F. S. & Tokatly, I. V. Singlet-triplet conversion and the long-range proximity effect in superconductor-ferromagnet structures with generic spin dependent fields. Phys. Rev. Lett. 110, 117003 (2013).

    Article  CAS  Google Scholar 

  23. Mel’nikov, A. S., Samokhvalov, A. V., Kuznetsova, S. M. & Buzdin, A. I. Interference phenomena and long-range proximity effect in clean superconductor-ferromagnet systems. Phys. Rev. Lett. 109, 237006 (2012).

    Article  Google Scholar 

  24. Klose, C. et al. Optimization of spin-triplet supercurrent in ferromagnetic Josephson junctions. Phys. Rev. Lett. 108, 127002 (2012).

    Article  Google Scholar 

  25. Glick, J. A. et al. Phase control in a spin-triplet SQUID. Sci. Adv. 4, eaat9457 (2018).

    Article  CAS  Google Scholar 

  26. Voltan, S., Singh, A. & Aarts, J. Triplet generation and upper critical field in superconducting spin valves based on CrO2. Phys. Rev. B 94, 054503 (2016).

    Article  Google Scholar 

  27. Visani, C. et al. Magnetic field influence on the proximity effect at YBa2Cu3O7/La2/3Ca1/3MnO3 superconductor/half-metal interfaces. Phys. Rev. B 92, 014519 (2015).

    Article  Google Scholar 

  28. Lahabi, K. et al. Controlling supercurrents and their spatial distribution in ferromagnets. Nat. Commun. 8, 2056 (2017).

    Article  Google Scholar 

  29. Shapiro, S. Josephson currents in superconducting tunneling: the effect of microwaves and other observations. Phys. Rev. Lett. 11, 80–82 (1963).

    Article  CAS  Google Scholar 

  30. Richard, C., Houzet, M. & Meyer, J. S. Superharmonic long-range triplet current in a diffusive Josephson junction. Phys. Rev. Lett. 110, 217004 (2013).

    Article  Google Scholar 

  31. Perez-Muñoz, A. M. et al. In operando evidence of deoxygenation in ionic liquid gating of YBa2Cu3O7-X. Proc. Natl Acad. Sci. USA 114, 215–220 (2017).

    Article  Google Scholar 

  32. Hoffmann, A. et al. Suppressed magnetization in La0.7Ca0.3MnO3 / YBa2Cu3O7–δ superlattices. Phys. Rev. B 72, 140407 (2005).

    Article  Google Scholar 

  33. Salafranca, J. & Okamoto, S. Unconventional proximity effect and inverse spin-switch behavior in a model manganite-cuprate-manganite trilayer system. Phys. Rev. Lett. 105, 256804 (2010).

    Article  Google Scholar 

  34. Schneider, C. W., Thiel, S., Hammerl, G., Richter, C. & Mannhart, J. Microlithography of electron gases formed at interfaces in oxide heterostructures. Appl. Phys. Lett. 89, 12–14 (2006).

    Article  Google Scholar 

  35. Bhatia, E. et al. Nanoscale domain wall engineered spin-triplet Josephson junctions and SQUID. Nano Lett. 21, 3092–3097 (2021).

    Article  CAS  Google Scholar 

  36. Ivanchenko, Y. M. & Zil’berman, L. A. The Josephson effect in small tunnel contacts. Sov. J. Exp. Theor. Phys. 28, 1272 (1969).

    Google Scholar 

  37. Dubos, P. et al. Josephson critical current in a long mesoscopic S-N-S junction. Phys. Rev. B 63, 064502 (2001).

    Article  Google Scholar 

  38. Anwar, M. S., Veldhorst, M., Brinkman, A. & Aarts, J. Long range supercurrents in ferromagnetic CrO2 using a multilayer contact structure. Appl. Phys. Lett. 100, 052602 (2012).

    Article  Google Scholar 

  39. Buzdin, A. Peculiar properties of the Josephson junction at the transition from 0 to π state. Phys. Rev. B 72, 100501(R) (2005).

    Article  Google Scholar 

  40. Houzet, M., Vinokur, V. & Pistolesi, F. Superharmonic Josephson relation at 0- / π-junction transition. Phys. Rev. B 72, 220506(R) (2005).

    Article  Google Scholar 

  41. Sellier, H., Baraduc, C., Lefloch, F. & Calemczuk, R. Half-integer shapiro steps at the 0–π crossover of a ferromagnetic Josephson junction. Phys. Rev. Lett. 92, 257005 (2004).

    Article  Google Scholar 

  42. Ryazanov, V. V. et al. Coupling of two superconductors through a ferromagnet: evidence for a π junction. Phys. Rev. Lett. 86, 2427–2430 (2001).

    Article  CAS  Google Scholar 

  43. Volkov, A. F. & Efetov, K. Proximity effect and its enhancement by ferromagnetism in high-temperature superconductor-ferromagnet structures. Phys. Rev. Lett. 102, 077002 (2009).

    Article  CAS  Google Scholar 

  44. Linder, J. & Robinson, J. W. A. Superconducting spintronics. Nat. Phys. 11, 307–315 (2015).

    Article  CAS  Google Scholar 

  45. Eschrig, M. Spin-polarized supercurrents for spintronics: a review of current progress. Rep. Prog. Phys. 78, 104501 (2015).

    Article  Google Scholar 

  46. Villegas, J. & Crete, D. G. Logic circuit based on spin valves of the spin-polarized supercurrent type and circuit integrating such logic gates. US patent 20170085269A1 (2017).

  47. Vernik, I. V. et al. Magnetic Josephson junctions with superconducting interlayer for cryogenic memory. IEEE Trans. Appl. Supercond. 23, 1701208 (2013).

    Article  Google Scholar 

  48. Ioffe, L. B., Geshkenbein, V. B., Feigel’man, M. V., Fauchère, A. L. & Blatter, G. Environmentally decoupled sds-wave Josephson junctions for quantum computing. Nature 398, 679–681 (1999).

    Article  Google Scholar 

  49. Mironov, S., Meng, H. & Buzdin, A. Magnetic flux pumping in superconducting loop containing a Josephson ψ junction. Appl. Phys. Lett. 116, 162601 (2020).

    Article  CAS  Google Scholar 

  50. Mironov, S. & Buzdin, A. Triplet proximity effect in superconducting heterostructures with a half-metallic layer. Phys. Rev. B 92, 184506 (2015).

    Article  Google Scholar 

Download references

Acknowledgements

We (J.S., C.L. and N.B.) acknowledge funding from the project Quantox of Quant ERA ERA-NET Cofund in Quantum Technologies (grant agreement no. 731473) implemented within the European Union’s Horizon 2020 programme. Work (J.S., C.L., F.M. and M.G.-H.) was supported by the Spanish AEI through grants MAT2015-72795-EXP, MAT2017-87134-C02 and PID2020-118078RB-I00. J.S. thanks the scholarship programme Alembert funded by the IDEX Paris-Saclay, ANR-11-IDEX-0003-02. Work at CNRS and the Thales lab (J.E.V.) was supported by ERC grant no. 647100 ‘SUSPINTRONICS’; J.E.V., A.I.B. and J.L. thank the French ANR grant ANR-15-CE24-0008-01 ‘SUPERTRONICS’, and J.E.V. and J.S. thank the COST action ‘Nanocohybri’. We (J.S., C.L. and J.-E.V.) acknowledge funding from the Flag ERA ERA-NET To2Dox project. We thank Helmholtz-Zentrum Berlin for the allocation of neutron/synchrotron radiation beamtime. This project received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 730872. J.S. thanks E. Strambini and F. Giazotto for collaboration in the early stages of this project. J.E.V. thanks C. Ulysse and L. Vila for collaboration in related projects. A.I.B. acknowledges support by the Ministry of Science and Higher Education of the Russian Federation within the framework of state funding for the creation and development of the world-class research center ‘Digital Biodesign and Personalized Healthcare’, no. 075-15-2020-926.

Author information

Authors and Affiliations

Authors

Contributions

D.S.-M. and F.A.C. grew the samples and performed resistance and critical current measurements. D.S.-M. and S.M. measured angle-dependent transport with contributions from A.S., X.P. and A.B.; D.S.-M., L.M. and S.V. measured X-ray absorption. D.S.-M. and S.M. measured Shapiro steps with the guidance and analysis of C.F.-P., N.B. and J.L.; A.I.B. contributed to the theoretical understanding and modelling. G.O., V.R., J.G.-B., M.R., F.G., J.T., A.R., F.M. and M.G.-H. worked on the sample growth and characterization in different stages of the project. M.C. and J.M.G.-C. performed the microscopy. J.S. designed the overall experiment, and J.E.V. contributed with the design of the Josephson characterization. J.S. and J.E.V. wrote the manuscript with the input and help of J.L., A.I.B., S.M., D.S.-M. and C.L. All authors discussed the results and revised the manuscript.

Corresponding authors

Correspondence to Javier E. Villegas or J. Santamaria.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Materials thanks the anonymous reviewers for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–8 and Discussion on the temperature and barrier thickness dependence of the critical current.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Sanchez-Manzano, D., Mesoraca, S., Cuellar, F.A. et al. Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet. Nat. Mater. 21, 188–194 (2022). https://doi.org/10.1038/s41563-021-01162-5

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41563-021-01162-5

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing