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.

  • Letter
  • Published:

Generation and detection of phase-coherent current-driven magnons in magnetic multilayers

Abstract

The magnetic state of a ferromagnet can affect the electrical transport properties of the material; for example, the relative orientation of the magnetic moments in magnetic multilayers1 underlies the phenomenon of giant magnetoresistance. The inverse effect—in which a large electrical current density can perturb the magnetic state of a multilayer—has been predicted2,3,4,5,6,7 and observed experimentally with point contacts8,9 and lithographically patterned samples10,11. Some of these observations were taken as indirect evidence for current-induced excitation of spin waves, or ‘magnons’. Here we probe directly the high-frequency behaviour and partial phase coherence of such current-induced excitations, by externally irradiating a point contact with microwaves. We determine the magnon spectrum and investigate how the magnon frequency and amplitude vary with the exciting current. Our observations support the feasibility of a spin-wave maser2 or ‘SWASER’ (spin-wave amplification by stimulated emission of radiation).

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

Figure 1: Experimental geometry and typical influence of the externally applied radiation on point-contact characteristics.
Figure 2: Phase diagram for the current-driven magnons.
Figure 3: Frequency variation of the current-driven magnons with magnetic field.
Figure 4: Variation of the amplitude of current-driven magnons with the exciting current.

Similar content being viewed by others

References

  1. Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472– 2475 (1988).

    Article  ADS  CAS  Google Scholar 

  2. Berger, L. Emission of spin waves by a magnetic multilayer traversed by a current. Phys. Rev. B 54, 9353–9358 (1996).

    Article  ADS  CAS  Google Scholar 

  3. Slonczewski, J. C. Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159, L1–L7 ( 1996).

    Article  ADS  CAS  Google Scholar 

  4. Berger, L. Multilayer as spin-wave emitting diodes. J. Appl. Phys. 81, 4880–4882 (1997).

    Article  ADS  CAS  Google Scholar 

  5. Bazaliy, Ya. B., Jones, B. A. & Zhang, S.-C. Modification of the Landau-Lifshitz equation in the presence of a spin-polarized current in colossal- and giant-magnetoresistive materials. Phys. Rev. B 57, R3213– R3216 (1998).

    Article  ADS  CAS  Google Scholar 

  6. Berger, L. Spin-wave emitting diodes and spin diffusion in magnetic multilayers. IEEE Trans. Magn. 34, 3837–3841 (1998).

    Article  ADS  Google Scholar 

  7. Slonczewski, J. C. Excitation of spin waves by an electric current. J. Magn. Magn. Mater. 195, L261–L268 ( 1999).

    Article  ADS  CAS  Google Scholar 

  8. Tsoi, M. et al. Excitation of a magnetic multilayer by an electric current. Phys. Rev. Lett. 80, 4281–4284 (1998).

    Article  ADS  CAS  Google Scholar 

  9. Myers, E. B., Ralph, D. C., Katine, J. A., Louie, R. N. & Buhrman, R. A. Current-induced switching of domains in magnetic multilayer devices. Science 285 , 867–870 (1999).

    Article  CAS  Google Scholar 

  10. Katine, J. A., Albert, F. J., Buhrman, R. A., Myers, E. B. & Ralph, D. C. Current-driven magnetization reversal and spin wave excitations in Co/Cu/Co pillars. Preprint cond-mat/9908231 at 〈xxx.lanl.gov〉 (1999).

  11. Sun, J. Z. Current-driven magnetic switching in manganite trilayer junctions. J. Magn. Magn. Mater. 202, 157–162 (1999).

    Article  ADS  CAS  Google Scholar 

  12. Jansen, A. G. M., van Gelder, A. P. & Wyder, P. Point-contact spectroscopy in metals. J. Phys. C 13, 6073–6118 ( 1980).

    Article  ADS  CAS  Google Scholar 

  13. Tsoi, M., Jansen, A. G. M. & Bass, J. Search for point-contact giant magnetoresistance in Co/Cu multilayers. J. Appl. Phys. 81, 5530 –5532 (1997).

    Article  ADS  CAS  Google Scholar 

  14. Seck, M. & Wyder, P. A sensitive broadband high-frequency electron spin resonance/electron nuclear double resonance spectrometer operating at 5-7. 5 mm wavelength. Rev. Sci. Instrum. 69, 1817–1822 (1998).

    Article  ADS  CAS  Google Scholar 

  15. van der Heijden, R. W., Jansen, A. G. M., Stoelinga, J. H. M., Swartjes, H. M. & Wyder, P. A new mechanism for high-frequency rectification at low temperatures in point contacts between identical metals. Appl. Phys. Lett. 37, 245–248 (1980).

    Article  ADS  CAS  Google Scholar 

  16. Javan, A. in Fundamental and Applied Laser Physics (eds Field, M. S., Javan, A. & Kurnit, N. A.) 295–334 (Wiley, New York, 1973).

    Google Scholar 

  17. Seavey, M. H. Jr & Tannenwald, P. E. Direct observation of spin-wave resonance. Phys. Rev. Lett. 1, 168–169 (1958).

    Article  ADS  CAS  Google Scholar 

  18. Herring, C. & Kittel, C. On the theory of spin waves in ferromagnetic media. Phys. Rev. 81, 869– 880 (1951).

    Article  ADS  Google Scholar 

  19. Damon, R. W. & Eshbach, J. R. Magnetostatic modes of a ferromagnet slab. J. Phys. Chem. Solids 19, 308– 320 (1961).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

This work was supported in part by the NSF, RU MNT, and RFFI.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to M. Tsoi.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Tsoi, M., Jansen, A., Bass, J. et al. Generation and detection of phase-coherent current-driven magnons in magnetic multilayers. Nature 406, 46–48 (2000). https://doi.org/10.1038/35017512

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/35017512

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

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