Abstract

Magnetic skyrmions are nanoscale topological spin structures offering great promise for next-generation information storage technologies. The recent discovery of sub-100-nm room-temperature (RT) skyrmions in several multilayer films has triggered vigorous efforts to modulate their physical properties for their use in devices. Here we present a tunable RT skyrmion platform based on multilayer stacks of Ir/Fe/Co/Pt, which we study using X-ray microscopy, magnetic force microscopy and Hall transport techniques. By varying the ferromagnetic layer composition, we can tailor the magnetic interactions governing skyrmion properties, thereby tuning their thermodynamic stability parameter by an order of magnitude. The skyrmions exhibit a smooth crossover between isolated (metastable) and disordered lattice configurations across samples, while their size and density can be tuned by factors of two and ten, respectively. We thus establish a platform for investigating functional sub-50-nm RT skyrmions, pointing towards the development of skyrmion-based memory devices.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1.

    A thermodynamic theory of weak ferromagnetism of antiferromagnetics. J. Phys. Chem. Solids 4, 241–255 (1958).

  2. 2.

    Anisotropic superexchange interaction and weak ferromagnetism. Phys. Rev. 120, 91–98 (1960).

  3. 3.

    & Thermodynamically stable magnetic vortex states in magnetic crystals. J. Magn. Magn. Mater. 138, 255–269 (1994).

  4. 4.

    , & Spontaneous skyrmion ground states in magnetic metals. Nature 442, 797–801 (2006).

  5. 5.

    et al. Skyrmion lattice in a chiral magnet. Science 323, 915–919 (2009).

  6. 6.

    et al. Real-space observation of a two-dimensional skyrmion crystal. Nature 465, 901–904 (2010).

  7. 7.

    & Topological properties and dynamics of magnetic skyrmions. Nat. Nanotech. 8, 899–911 (2013).

  8. 8.

    , & Skyrmions on the track. Nat. Nanotech. 8, 152–156 (2013).

  9. 9.

    , , , & Nucleation, stability and current-induced motion of isolated magnetic skyrmions in nanostructures. Nat. Nanotech. 8, 839–844 (2013).

  10. 10.

    , , , & Stability of single skyrmionic bits. Nat. Commun. 6, 8455 (2015).

  11. 11.

    et al. Spontaneous atomic-scale magnetic skyrmion lattice in two dimensions. Nat. Phys. 7, 713–718 (2011).

  12. 12.

    et al. Writing and deleting single magnetic skyrmions. Science 341, 636–639 (2013).

  13. 13.

    et al. Emergent electrodynamics of skyrmions in a chiral magnet. Nat. Phys. 8, 301–304 (2012).

  14. 14.

    Magnetic and transport properties of metallic multilayers. Mater. Sci. Forum 59–60, 439–480 (1990).

  15. 15.

    et al. Chiral magnetic order at surfaces driven by inversion asymmetry. Nature 447, 190–193 (2007).

  16. 16.

    , , & Emergent phenomena induced by spin-orbit coupling at surfaces and interfaces. Nature 539, 509–517 (2016).

  17. 17.

    , & Dzyaloshinskii–Moriya interaction accounting for the orientation of magnetic domains in ultrathin films: Fe/W(110). Phys. Rev. B 78, 140403 (2008).

  18. 18.

    et al. Thickness dependence of the interfacial Dzyaloshinskii–Moriya interaction in inversion symmetry broken systems. Nat. Commun. 6, 7635 (2015).

  19. 19.

    , , & Tailoring magnetic skyrmions in ultra-thin transition metal films. Nat. Commun. 5, 4030 (2014).

  20. 20.

    , , , & Anatomy of Dzyaloshinskii–Moriya interaction at Co/Pt interfaces. Phys. Rev. Lett. 115, 267210 (2015).

  21. 21.

    et al. Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature. Nat. Nanotech. 11, 444–448 (2016).

  22. 22.

    et al. Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets. Nat. Mater. 15, 501–506 (2016).

  23. 23.

    et al. Room-temperature chiral magnetic skyrmions in ultrathin magnetic nanostructures. Nat. Nanotech. 11, 449–454 (2016).

  24. 24.

    , , & Room temperature skyrmion ground state stabilized through interlayer exchange coupling. Appl. Phys. Lett. 106, 242404 (2015).

  25. 25.

    , & Interlayer exchange coupling: a general scheme turning chiral magnets into magnetic multilayers carrying atomic-scale skyrmions. Phys. Rev. Lett. 116, 177202 (2016).

  26. 26.

    et al. Blowing magnetic skyrmion bubbles. Science 349, 283–286 (2015).

  27. 27.

    et al. Dynamics and inertia of skyrmionic spin structures. Nat. Phys. 11, 225–228 (2015).

  28. 28.

    , , & Chiral skyrmions in thin magnetic films: new objects for magnetic storage technologies? J. Phys. D 44, 392001 (2011).

  29. 29.

    & Skyrmion confinement in ultrathin film nanostructures in the presence of Dzyaloshinskii–Moriya interaction. Phys. Rev. B 88, 184422 (2013).

  30. 30.

    et al. The properties of isolated chiral skyrmions in thin magnetic films. New J. Phys. 18, 065003 (2016).

  31. 31.

    et al. A strategy for the design of skyrmion racetrack memories. Sci. Rep. 4, 6784 (2014).

  32. 32.

    , , , & Magnetic skyrmion transistor: skyrmion motion in a voltage-gated nanotrack. Sci. Rep. 5, 11369 (2015).

  33. 33.

    et al. Topological Hall effect in the A phase of MnSi. Phys. Rev. Lett. 102, 186602 (2009).

  34. 34.

    et al. Skyrmions in a doped antiferromagnet. Phys. Rev. Lett. 106, 227206 (2011).

  35. 35.

    , & Scattering mechanisms in textured FeGe thin films: magnetoresistance and the anomalous Hall effect. Phys. Rev. B 90, 024403 (2014).

  36. 36.

    et al. Unwinding of a skyrmion lattice by magnetic monopoles. Science 340, 1076–1080 (2013).

  37. 37.

    , , , & Engineering skyrmions in transition-metal multilayers for spintronics. Nat. Commun. 7, 11779 (2016).

  38. 38.

    , , , & Controlling Dzyaloshinskii–Moriya interaction via chirality dependent layer stacking, insulator capping and electric field. Preprint at (2016).

  39. 39.

    , , & Magnetic anisotropy in metallic multilayers. Rep. Prog. Phys. 59, 1409–1458 (1999).

  40. 40.

    , , & Anomalous Hall effect. Rev. Mod. Phys. 82, 1539–1592 (2010).

  41. 41.

    & Extended skyrmion phase in epitaxial FeGe(111) thin films. Phys. Rev. Lett. 108, 267201 (2012).

  42. 42.

    et al. Interface-driven topological Hall effect in SrRuO3–SrIrO3 bilayer. Sci. Adv. 2, e1600304 (2016).

  43. 43.

    et al. Dopant clustering, electronic inhomogeneity, and vortex pinning in iron-based superconductors. Phys. Rev. B 87, 214519 (2013).

  44. 44.

    , & Magnetic domain-wall racetrack memory. Science 320, 190–194 (2008).

  45. 45.

    et al. Voltage controlled magnetic skyrmion motion for racetrack memory. Sci. Rep. 6, 23164 (2016).

  46. 46.

    et al. The design and verification of MuMax3. AIP Adv. 4, 107133 (2014).

  47. 47.

    & Magnetic Domain Walls in Bubble Materials 1st edn (Academic, 1979).

Download references

Acknowledgements

We acknowledge K. Masgrau, S. He and B. Satywali for experimental inputs, W. S. Lew for allowing us to access his instruments, and P. Fischer, O. Auslaender and A. Fert for insightful discussions. We also acknowledge the support of the A*STAR Computational Resource Center (A*CRC), Singapore and the National Supercomputing Centre (NSCC), Singapore for performing computational work. This work was supported by the Singapore Ministry of Education (MoE), Academic Research Fund Tier 2 (Ref. No. MOE2014-T2-1-050), the National Research Foundation (NRF) of Singapore, NRF - Investigatorship (Ref. No.: NRF-NRFI2015-04), and the A*STAR Pharos Fund (Ref. No. 1527400026) of Singapore. M.Y.I. acknowledges support from Leading Foreign Research Institute Recruitment Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Education, Science and Technology (MEST) (2012K1A4A3053565) and by the DGIST R&D programme of the Ministry of Science, ICT and future Planning (17-BT-02). The work at ALS was supported by the Director, Office of Science, Office of Basic Energy Sciences, Scientific User Facilities Division of the US Department of Energy under Contract No. DE-AC02-05CH11231.

Author information

Author notes

    • A. L. Gonzalez Oyarce
    •  & Anthony K. C. Tan

    Present addresses: Institute of High Performance Computing, 1 Fusionopolis Way, 138632, Singapore (A.L.G.O.); Data Storage Institute, 2 Fusionopolis Way, 138634, Singapore (A.K.C.T.).

Affiliations

  1. Data Storage Institute, 2 Fusionopolis Way, 138634, Singapore

    • Anjan Soumyanarayanan
    • , A. L. Gonzalez Oyarce
    • , Pin Ho
    • , M. Tran
    •  & F. Ernult
  2. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore

    • Anjan Soumyanarayanan
    • , M. Raju
    • , Anthony K. C. Tan
    • , A. P. Petrović
    •  & C. Panagopoulos
  3. Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    • Mi-Young Im
  4. Department of Emerging Materials Science, DGIST, Daegu 42988, Korea

    • Mi-Young Im
  5. Institute of High Performance Computing, 1 Fusionopolis Way, 138632, Singapore

    • K. H. Khoo
    •  & C. K. Gan

Authors

  1. Search for Anjan Soumyanarayanan in:

  2. Search for M. Raju in:

  3. Search for A. L. Gonzalez Oyarce in:

  4. Search for Anthony K. C. Tan in:

  5. Search for Mi-Young Im in:

  6. Search for A. P. Petrović in:

  7. Search for Pin Ho in:

  8. Search for K. H. Khoo in:

  9. Search for M. Tran in:

  10. Search for C. K. Gan in:

  11. Search for F. Ernult in:

  12. Search for C. Panagopoulos in:

Contributions

A.S., M.T., F.E. and C.P. designed and initiated the research. M.R. deposited the films, and characterized them with A.S. M.Y.I. conducted the MTXM experiments. A.K.C.T. performed the MFM experiments and analysed the imaging data with A.S., and P.H. validated the MFM results. M.R. and A.P.P. performed transport experiments and analysed the data with A.S. A.L.G.O. performed micromagnetic simulations. K.H.K. and C.K.G. carried out the DFT calculations. A.S. and C.P. coordinated the project and wrote the manuscript. All authors discussed the results and provided inputs to the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Anjan Soumyanarayanan or C. Panagopoulos.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Information

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/nmat4934

Further reading