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.

# Direct probing of the exchange interaction at buried interfaces

## Abstract

The fundamental interactions between magnetic moments at interfaces have an important impact on the properties of layered magnetic structures. Hence, a direct probing of these interactions is highly desirable for understanding a wide range of phenomena in low-dimensional solids. Here we propose a method for probing the magnetic exchange interaction at buried interfaces using spin-polarized electrons and taking advantage of the collective nature of elementary magnetic excitations (magnons). We demonstrate that, for the case of weak coupling at the interface, the low-energy magnon mode is mainly localized at the interface. Because this mode has the longest lifetime of the modes and has a finite spectral weight across the layers on top, it can be probed by electrons. A comparison of experimental data and first-principles calculations leads to the determination of the interface exchange parameters. This method may help the development of spectroscopy of buried magnetic interfaces.

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

## Relevant articles

• ### Unconventional magnonic surface and interface states in layered ferromagnets

Communications Physics Open Access 04 February 2021

• ### Ultrafast dynamics of exchange stiffness in Co/Pt multilayer

Communications Physics Open Access 06 May 2020

• ### A multiscale model of the effect of Ir thickness on the static and dynamic properties of Fe/Ir/Fe films

Scientific Reports Open Access 01 March 2018

## Access options

\$32.00

All prices are NET prices.

## References

1. Nolting, F. et al. Direct observation of the alignment of ferromagnetic spins by antiferromagnetic spins. Nature 405, 767–769 (2000).

2. Mills, D. L. Surface corrections to the specific heat of ferromagnetic films. Phys. Rev. B 1, 264–274 (1970).

3. Costa, A. T., Muniz, R. B. & Mills, D. L. Spin waves and their damping in itinerant ultrathin ferromagnets: intermediate wave vectors. Phys. Rev. B 74, 214403 (2006).

4. Ibach, H. et al. A novel spectrometer for spin-polarized electron energy-loss spectroscopy. Rev. Sci. Instrum. 74, 4089–4095 (2003).

5. Ibach, H., Rajeswari, J. & Schneider, C. M. An electron energy loss spectrometer designed for studies of electronic energy losses and spin waves in the large momentum regime. Rev. Sci. Instrum. 82, 123904 (2011).

6. Vollmer, R., Etzkorn, M., Kumar, P. S. A., Ibach, H. & Kirschner, J. Spin-polarized electron energy loss spectroscopy of high energy, large wave vector spin waves in ultrathin fcc Co films on Cu(001). Phys. Rev. Lett. 91, 147201 (2003).

7. Heinrich, A. J., Gupta, J. A., Lutz, C. P. & Eigler, D. M. Single-atom spin-flip spectroscopy. Science 306, 466–469 (2004).

8. Balashov, T., Takács, A. F., Wulfhekel, W. & Kirschner, J. Magnon excitation with spin-polarized scanning tunneling microscopy. Phys. Rev. Lett. 97, 187201 (2006).

9. Tang, W. X. et al. Large wave vector spin waves and dispersion in two monolayer Fe on w(110). Phys. Rev. Lett. 99, 087202 (2007).

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

11. Prokop, J. et al. Magnons in a ferromagnetic monolayer. Phys. Rev. Lett. 102, 177206 (2009).

12. Zhang, Y. et al. Nonmonotonic thickness dependence of spin wave energy in ultrathin Fe films: experiment and theory. Phys. Rev. B 81, 094438 (2010).

13. Zakeri, K. et al. Asymmetric spin-wave dispersion on Fe(110): direct evidence of the Dzyaloshinskii–Moriya interaction. Phys. Rev. Lett. 104, 137203 (2010).

14. Zakeri, K., Zhang, Y., Chuang, T-H. & Kirschner, J. Magnon lifetimes on the Fe(110) surface: the role of spin–orbit coupling. Phys. Rev. Lett. 108, 197205 (2012).

15. Hong, J. & Mills, D. L. Theory of the spin dependence of the inelastic mean free path of electrons in ferromagnetic metals: a model study. Phys. Rev. B 59, 13840–13848 (1999).

16. Hong, J. & Mills, D. L. Spin dependence of the inelastic electron mean free path in Fe and Ni: explicit calculations and implications. Phys. Rev. B 62, 5589–5600 (2000).

17. Zakeri, K. & Kirschner, J. in Probing Magnons by Spin-Polarized Electrons Ch. 7, 84–99 (Topics in Applied Physics Magnonics From Fundamentals to Applications 125, Springer, 2013).

18. Zhang, Y., Chuang, T-H., Zakeri, K. & Kirschner, J. Relaxation time of terahertz magnons excited at ferromagnetic surfaces. Phys. Rev. Lett. 109, 087203 (2012).

19. Martin, V. et al. Pseudomorphic growth of Fe monolayers on Ir(001)(1×1): from a fct precursor to a bct film. Phys. Rev. B 76, 205418 (2007).

20. Zakeri, K., Zhang, Y. & Kirschner, J. Surface magnons probed by spin-polarized electron energy loss spectroscopy. J. Electron Spectrosc. Rel. Phenom. http://dx.doi.org/10.1016/j.elspec.2012.06.009 (in the press).

21. Buczek, P., Ernst, A. & Sandratskii, L. M. Different dimensionality trends in the landau damping of magnons in iron, cobalt, and nickel: time-dependent density functional study. Phys. Rev. B 84, 174418 (2011).

22. Zakeri, K., Peixoto, T., Zhang, Y., Prokop, J. & Kirschner, J. On the preparation of clean tungsten single crystals. Surf. Sci. 604, L1–L3 (2010).

23. Deák, A., Szunyogh, L. & Ujfalussy, B. Thickness-dependent magnetic structure of ultrathin Fe/Ir(001) films: from spin-spiral states toward ferromagnetic order. Phys. Rev. B 84, 224413 (2011).

24. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

25. Lüders, M., Ernst, A., Temmerman, W. M., Szotek, Z. & Durham, P. J. Ab initio angle-resolved photoemission in multiple-scattering formulation. J. Phys. 13, 8587–8606 (2001).

26. Liechtenstein, A. I., Katsnelson, M. I., Antropov, V. P. & Gubanov, V. A. Local spin density functional approach to the theory of exchange interactions in ferromagnetic metals and alloys. J. Magn. Magn. Mater. 67, 65–74 (1987).

## Acknowledgements

A.E. acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG priority programme SPP 1538 ‘Spin Caloric Transport’). The calculations were performed at the Rechenzentrum Garching of the Max Planck Society.

## Author information

Authors

### Contributions

Kh.Z. supervised the project, conceived and planned the experiments, participated in the analysis of the experimental data and wrote the paper. T.-H.C. carried out the experiments and analysed the experimental data. A.E. and P.B. performed the theoretical calculations. A.E. analysed the theoretical results. L.M.S. participated in the analysis of the theoretical results, the development of the structure of the paper and in writing the paper. H.J.Q. performed one part of the experiments and analysed the experimental data. Y.Z. contributed to the experiments. J.K. supervised the project. All authors contributed to the discussion of the results and improving the manuscript.

### Corresponding author

Correspondence to Kh. Zakeri.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary information

Supplementary information (PDF 1103 kb)

## Rights and permissions

Reprints and Permissions

Zakeri, K., Chuang, TH., Ernst, A. et al. Direct probing of the exchange interaction at buried interfaces. Nature Nanotech 8, 853–858 (2013). https://doi.org/10.1038/nnano.2013.188

• Accepted:

• Published:

• Issue Date:

• DOI: https://doi.org/10.1038/nnano.2013.188

• ### Characterization of magnons created inside the bulk and at the surface of ferromagnetic multilayer $$\text {Co}_{1-x}\text {Fe}_{x}/\text {Cu}$$

• Ahmed Qachaou
• Mohamed Lharch

Applied Physics A (2022)

• ### Unconventional magnonic surface and interface states in layered ferromagnets

• Khalil Zakeri
• Huajun Qin
• Arthur Ernst

Communications Physics (2021)

• ### Ultrafast dynamics of exchange stiffness in Co/Pt multilayer

• Je-Ho Shim
• Akbar Ali Syed
• Dong Eon Kim

Communications Physics (2020)

• ### A multiscale model of the effect of Ir thickness on the static and dynamic properties of Fe/Ir/Fe films

• László Oroszlány
• Thomas A. Ostler

Scientific Reports (2018)

• ### Long-living terahertz magnons in ultrathin metallic ferromagnets

• H. J. Qin
• Kh. Zakeri
• J. Kirschner

Nature Communications (2015)