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Imaging of spin waves in atomically designed nanomagnets

Nature Materials volume 13, pages 782–785 (2014)Cite this article

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Abstract

The spin dynamics of all ferromagnetic materials are governed by two types of collective phenomenon: spin waves and domain walls. The fundamental processes underlying these collective modes, such as exchange interactions and magnetic anisotropy, all originate at the atomic scale. However, conventional probing techniques based on neutron1 and photon scattering2 provide high resolution in reciprocal space, and thereby poor spatial resolution. Here we present direct imaging of standing spin waves in individual chains of ferromagnetically coupled S = 2 Fe atoms, assembled one by one on a Cu2N surface using a scanning tunnelling microscope. We are able to map the spin dynamics of these designer nanomagnets with atomic resolution in two complementary ways. First, atom-to-atom variations of the amplitude of the quantized spin-wave excitations are probed using inelastic electron tunnelling spectroscopy. Second, we observe slow stochastic switching between two opposite magnetization states3,4, whose rate varies strongly depending on the location of the tip along the chain. Our observations, combined with model calculations, reveal that switches of the chain are initiated by a spin-wave excited state that has its antinodes at the edges of the chain, followed by a domain wall shifting through the chain from one end to the other. This approach opens the way towards atomic-scale imaging of other types of spin excitation, such as spinon pairs and fractional end-states5,6, in engineered spin chains.

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Figure 1: Magnetic switching of a ferromagnetic spin chain.
Figure 2: Observation of spin-wave states.
Figure 3: Time evolution of the switching process.
Figure 4: Current and bias dependences of the switching rates.

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References

  1. Mourigal, M. et al. Fractional spinon excitations in the quantum Heisenberg antiferromagnetic chain. Nature Phys. 9, 435–441 (2013).

    Article  CAS  Google Scholar 

  2. Kampfrath, T. et al. Coherent terahertz control of antiferromagnetic spin waves. Nature Photon. 5, 31–34 (2010).

    Article  Google Scholar 

  3. Loth, S., Baumann, S., Lutz, C. P., Eigler, D. M. & Heinrich, A. J. Bistability in atomic-scale antiferromagnets. Science 335, 196–199 (2012).

    Article  CAS  Google Scholar 

  4. Khajetoorians, A. A. et al. Current-driven spin dynamics of artificially constructed quantum magnets. Science 339, 55–59 (2013).

    Article  CAS  Google Scholar 

  5. Balents, L. Spin liquids in frustrated magnets. Nature 464, 199–208 (2010).

    Article  CAS  Google Scholar 

  6. Delgado, F., Batista, C. D. & Fernández-Rossier, J. Local probe of fractional edge states of S = 1 Heisenberg spin chains. Phys. Rev. Lett. 111, 167201 (2013).

    Article  CAS  Google Scholar 

  7. Rohart, S. et al. Spin-wave-assisted thermal reversal of epitaxial perpendicular magnetic nanodots. Phys. Rev. Lett. 104, 137202 (2010).

    Article  CAS  Google Scholar 

  8. Acremann, Y. et al. Time-resolved imaging of spin transfer switching: Beyond the macrospin concept. Phys. Rev. Lett. 96, 217202 (2006).

    Article  CAS  Google Scholar 

  9. Mangin, S. et al. Current-induced magnetization reversal in nanopillars with perpendicular anisotropy. Nature Mater. 5, 210–215 (2006).

    Article  CAS  Google Scholar 

  10. Sankey, J. C. et al. Measurement of the spin-transfer-torque vector in magnetic tunnel junctions. Nature Phys. 4, 67–71 (2007).

    Article  Google Scholar 

  11. Park, J., Eames, P., Engebretson, D., Berezovsky, J. & Crowell, P. Spatially resolved dynamics of localized spin-wave modes in ferromagnetic wires. Phys. Rev. Lett. 89, 277201 (2002).

    Article  CAS  Google Scholar 

  12. Puzic, A. et al. Spatially resolved ferromagnetic resonance: Imaging of ferromagnetic eigenmodes. J. Appl. Phys. 97, 10E704 (2005).

    Article  Google Scholar 

  13. Heinze, S. et al. Real-space imaging of two-dimensional antiferromagnetism on the atomic scale. Science 288, 1805–1808 (2000).

    Article  CAS  Google Scholar 

  14. Hirjibehedin, C. F., Lutz, C. P. & Heinrich, A. J. Spin coupling in engineered atomic structures. Science 312, 1021–1024 (2006).

    Article  CAS  Google Scholar 

  15. Khajetoorians, A. A., Wiebe, J., Chilian, B. & Wiesendanger, R. Realizing all-spin-based logic operations atom by atom. Science 332, 1062–1064 (2011).

    Article  CAS  Google Scholar 

  16. Zhou, L. et al. Strength and directionality of surface Ruderman–Kittel–Kasuya–Yosida interaction mapped on the atomic scale. Nature Phys. 6, 187–191 (2010).

    Article  CAS  Google Scholar 

  17. Bryant, B., Spinelli, A., Wagenaar, J. J. T., Gerrits, M. & Otte, A. F. Local control of single atom magnetocrystalline anisotropy. Phys. Rev. Lett. 111, 127203 (2013).

    Article  CAS  Google Scholar 

  18. Loth, S. et al. Controlling the state of quantum spins with electric currents. Nature Phys. 6, 340–344 (2010).

    Article  CAS  Google Scholar 

  19. Stipe, B. C. Single-molecule vibrational spectroscopy and microscopy. Science 280, 1732–1735 (1998).

    Article  CAS  Google Scholar 

  20. Hirjibehedin, C. F. et al. Large magnetic anisotropy of a single atomic spin embedded in a surface molecular network. Science 317, 1199–1203 (2007).

    Article  CAS  Google Scholar 

  21. Otte, A. F. et al. Spin excitations of a Kondo-screened atom coupled to a second magnetic atom. Phys. Rev. Lett. 103, 107203 (2009).

    Article  CAS  Google Scholar 

  22. Gao, C. et al. Spin wave dispersion on the nanometer scale. Phys. Rev. Lett. 101, 167201 (2008).

    Article  CAS  Google Scholar 

  23. Fernández-Rossier, J. Theory of single-spin inelastic tunneling spectroscopy. Phys. Rev. Lett. 102, 256802 (2009).

    Article  Google Scholar 

  24. Persson, M. Theory of inelastic electron tunneling from a localized spin in the impulsive approximation. Phys. Rev. Lett. 103, 050801 (2009).

    Article  Google Scholar 

  25. Fransson, J. Spin inelastic electron tunneling spectroscopy on local spin adsorbed on surface. Nano Lett. 9, 2414–2417 (2009).

    Article  CAS  Google Scholar 

  26. Lorente, N. & Gauyacq, J-P. Efficient spin transitions in inelastic electron tunneling spectroscopy. Phys. Rev. Lett. 103, 176601 (2009).

    Article  Google Scholar 

  27. Gauyacq, J-P., Yaro, S., Cartoixà, X. & Lorente, N. Correlation-mediated processes for electron-induced switching between Néel states of Fe antiferromagnetic chains. Phys. Rev. Lett. 110, 087201 (2013).

    Article  Google Scholar 

  28. Gauyacq, J. P. & Lorente, N. Magnetic reversal of a quantum nanoferromagnet. Phys. Rev. B 87, 195402 (2013).

    Article  Google Scholar 

  29. Delgado, F. & Fernández-Rossier, J. Spin dynamics of current-driven single magnetic adatoms and molecules. Phys. Rev. B 82, 134414 (2010).

    Article  Google Scholar 

  30. Sonntag, A. et al. Electric-field-induced magnetic anisotropy in a nanomagnet investigated on the atomic scale. Phys. Rev. Lett. 112, 017204 (2014).

    Article  CAS  Google Scholar 

  31. Oberg, J. C. et al. Control of single-spin magnetic anisotropy by exchange coupling. Nature Nanotech. 9, 64–68 (2014).

    Article  CAS  Google Scholar 

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Acknowledgements

This work was supported by the Dutch funding organizations FOM and NWO (VIDI) and by the Kavli Foundation. F.D. and J.F-R. acknowledge support from the Ministry of Science and Education Spain (FIS2010-21883-C02-01) and from GV grant Prometeo (ACOMP/2010/070).

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Authors and Affiliations

  1. Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands

    A. Spinelli, B. Bryant & A. F. Otte

  2. International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal

    F. Delgado & J. Fernández-Rossier

Authors
  1. A. Spinelli
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  2. B. Bryant
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  3. F. Delgado
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  4. J. Fernández-Rossier
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  5. A. F. Otte
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Contributions

A.S. and B.B. performed the measurements and analysed the results. F.D. and J.F-R. performed the master equation calculations and provided theoretical support. A.F.O. conceived the experiment and supervised the work. All authors contributed to writing the manuscript and gave critical comments.

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Correspondence to A. F. Otte.

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The authors declare no competing financial interests.

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Spinelli, A., Bryant, B., Delgado, F. et al. Imaging of spin waves in atomically designed nanomagnets. Nature Mater 13, 782–785 (2014). https://doi.org/10.1038/nmat4018

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