Skip to main content
Log in

Microwave oscillations of a nanomagnet driven by a spin-polarized current

  • Letter
  • Published:

From Nature

View current issue Submit your manuscript

Abstract

The recent discovery that a spin-polarized electrical current can apply a large torque to a ferromagnet, through direct transfer of spin angular momentum, offers the possibility of manipulating magnetic-device elements without applying cumbersome magnetic fields1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16. However, a central question remains unresolved: what type of magnetic motions can be generated by this torque? Theory predicts that spin transfer may be able to drive a nanomagnet into types of oscillatory magnetic modes not attainable with magnetic fields alone1,2,3, but existing measurement techniques have provided only indirect evidence for dynamical states4,6,7,8,12,14,15,16. The nature of the possible motions has not been determined. Here we demonstrate a technique that allows direct electrical measurements of microwave-frequency dynamics in individual nanomagnets, propelled by a d.c. spin-polarized current. We show that spin transfer can produce several different types of magnetic excitation. Although there is no mechanical motion, a simple magnetic-multilayer structure acts like a nanoscale motor; it converts energy from a d.c. electrical current into high-frequency magnetic rotations that might be applied in new devices including microwave sources and resonators.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Figure 1: Resistance and microwave data for sample 1.
Figure 2: Resistance and microwave data for sample 2.
Figure 3: Results of numerical solution of the Landau–Lifshitz–Gilbert equation for a single-domain nanomagnet at zero temperature.

Similar content being viewed by others

References

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

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

    Article  ADS  CAS  Google Scholar 

  4. Tsoi, M. et al. Excitation of a magnetic multilayer by an electric current. Phys. Rev. Lett. 80, 4281–4284 (1998); erratum Phys. Rev. Lett. 81, 493 (1998)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  6. 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 

  7. 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. Phys. Rev. Lett. 84, 4212–4215 (2000)

    Article  Google Scholar 

  8. Tsoi, M. et al. Generation and detection of phase-coherent current-driven magnons in magnetic multilayers. Nature 406, 46–48 (2000)

    Article  ADS  CAS  Google Scholar 

  9. Grollier, J. et al. Spin-polarized current induced switching in Co/Cu/Co pillars. Appl. Phys. Lett. 78, 3663–3665 (2001)

    Article  ADS  CAS  Google Scholar 

  10. Stiles, M. D. & Zangwill, A. Anatomy of spin-transfer torque. Phys. Rev. B 65, 014407 (2002)

    Article  ADS  Google Scholar 

  11. Wegrowe, J.-E. et al. Exchange torque and spin transfer between spin polarized current and ferromagnetic layers. Appl. Phys. Lett. 80, 3775–3777 (2002)

    Article  ADS  CAS  Google Scholar 

  12. Sun, J. Z., Monsma, D. J., Abraham, D. W., Rooks, M. J. & Koch, R. H. Batch-fabricated spin-injection magnetic switches. Appl. Phys. Lett. 81, 2202–2204 (2002)

    Article  ADS  CAS  Google Scholar 

  13. Bauer, G. E. W., Tserkovnyak, Y., Huertas-Hernando, D. & Brataas, A. Universal angular magnetoresistance and spin torque in ferromagnetic/normal metal hybrids. Phys. Rev. B 67, 094421 (2003)

    Article  ADS  Google Scholar 

  14. Rippard, W. H., Pufall, M. R. & Silva, T. J. Quantitative studies of spin-momentum-transfer-induced excitations in Co/Cu multilayer films using point-contact spectroscopy. Appl. Phys. Lett. 82, 1260–1262 (2003)

    Article  ADS  CAS  Google Scholar 

  15. Özyilmaz, B. et al. Current-induced magnetization reversal in high magnetic fields in Co/Cu/Co nanopillars. Phys. Rev. Lett. 91, 067203 (2003)

    Article  ADS  Google Scholar 

  16. Urazhdin, S., Birge, N. O., Pratt, W. P. Jr & Bass, J. Current-driven magnetic excitations in permalloy-based multilayer nanopillars. Preprint at 〈http://arXiv:cond-mat/0303149〉 (2003).

  17. Albert, F. J. The Fabrication and Measurement of Current Perpendicular to the Plane Magnetic Nanostructures for the Study of the Spin Transfer Effect. PhD dissertation, Cornell Univ. (2003)

    Google Scholar 

  18. 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 

  19. Pozar, D. M. Microwave Engineering 2nd edn, 566 (John Wiley & Sons, New York, 1998)

    Google Scholar 

  20. Kittel, C. Introduction to Solid State Physics 7th edn, 505 (John Wiley & Sons, New York, 1996)

    Google Scholar 

  21. Johnson, M. T., Bloemen, P. J. H., den Broeder, F. J. A. & de Vries, J. J. Magnetic anisotropy in metallic multilayers. Rep. Prog. Phys. 59, 1409–1458 (1996)

    Article  ADS  CAS  Google Scholar 

  22. Lee, C. H. et al. Magnetic anisotropy in epitaxial Co superlattices. Phys. Rev. B 42, 1066–1069 (1990)

    Article  ADS  CAS  Google Scholar 

  23. Myers, E. B. et al. Thermally activated magnetic reversal induced by a spin-polarized current. Phys. Rev. Lett. 89, 196801 (2002)

    Article  ADS  CAS  Google Scholar 

  24. Nazarov, A. V., Cho, H. S., Nowak, J., Stokes, S. & Tabat, N. Tunable ferromagnetic resonance peak in tunneling magnetoresistive sensor structures. Appl. Phys. Lett. 81, 4559–4561 (2002)

    Article  ADS  CAS  Google Scholar 

  25. Sun, J. Z. Spin-current interaction with a monodomain magnetic body: A model study. Phys. Rev. B 62, 570–578 (2000)

    Article  ADS  CAS  Google Scholar 

  26. Bazaliy, Y. B., Jones, B. A. & Zhang, S. C. Towards metallic magnetic memory: How to interpret experimental results on magnetic switching induced by spin-polarized currents. J. Appl. Phys. 89, 6793–6795 (2001)

    Article  ADS  CAS  Google Scholar 

  27. Grollier, J. et al. Field dependence of magnetization reversal by spin transfer. Phys. Rev. B 67, 174402 (2003)

    Article  ADS  Google Scholar 

  28. Li, Z. & Zhang, S. Magnetization dynamics with a spin-transfer torque. Phys. Rev. B 68, 024404 (2003)

    Article  ADS  Google Scholar 

  29. Suhl, H. The theory of ferromagnetic resonance at high signal powers. J. Phys. Chem. Solids 1, 209–227 (1957)

    Article  ADS  Google Scholar 

  30. Polianski, M. & Brouwer, P. W. Current-induced transverse spin wave instability in a thin nanomagnet. Preprint at 〈http://arxiv.org/abs/cond-mat/0304069〉 (2003).

Download references

Acknowledgements

We thank K. W. Lehnert, I. Siddiqi and other members of the groups of R. J. Schoelkopf, D. E. Prober and M. H. Devoret for advice about microwave measurements. We acknowledge support from DARPA through Motorola, from the Army Research Office, and from the NSF/NSEC programme through the Cornell Center for Nanoscale Systems. We also acknowledge use of the NSF-supported Cornell Nanofabrication Facility/NNUN.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to D. C. Ralph.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Kiselev, S., Sankey, J., Krivorotov, I. et al. Microwave oscillations of a nanomagnet driven by a spin-polarized current. Nature 425, 380–383 (2003). https://doi.org/10.1038/nature01967

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature01967

  • Springer Nature Limited

This article is cited by

Navigation