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Magnetic vortex oscillator driven by d.c. spin-polarized current

Abstract

Transfer of angular momentum from a spin-polarized current to a ferromagnet provides an efficient means to control the magnetization dynamics of nanomagnets. A peculiar consequence of this spin torque, the ability to induce persistent oscillations in a nanomagnet by applying a d.c. current, has previously been reported only for spatially uniform nanomagnets. Here, we demonstrate that a quintessentially non-uniform magnetic structure, a magnetic vortex, isolated within a nanoscale spin-valve structure, can be excited into persistent microwave-frequency oscillations by a spin-polarized d.c. current. Comparison with micromagnetic simulations leads to identification of the oscillations with a precession of the vortex core. The oscillations, which can be obtained in essentially zero magnetic field, exhibit linewidths that can be narrower than 300 kHz at 1.1 GHz, making these highly compact spin-torque vortex-oscillator devices potential candidates for microwave signal-processing applications, and a powerful new tool for fundamental studies of vortex dynamics in magnetic nanostructures.

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Figure 1: GMR and microwave data for sample 1.
Figure 2: Micromagnetic simulation for I=6.6 mA and H =200Oe.
Figure 3: Dependence of microwave frequencies on H for sample 2.
Figure 4: Dependence of microwave frequencies on H for sample 1.

References

  1. 1

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

    ADS  Article  Google Scholar 

  2. 2

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

    ADS  Article  Google Scholar 

  3. 3

    Kiselev, S. I. et al. Microwave oscillations of a nanomagnet driven by a spin-polarized current. Nature 425, 380–383 (2003).

    ADS  Article  Google Scholar 

  4. 4

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

    ADS  Article  Google Scholar 

  5. 5

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

    ADS  Article  Google Scholar 

  6. 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  Google Scholar 

  7. 7

    Katine, J. A., Albert, F. J., Buhrman, R. A., Myers, & Ralph, D. C. Current-driven magnetization reversal and spin-wave excitations in Co/Cu/Co pillars. Phys. Rev. Lett. 84, 3149–3152 (2000).

    ADS  Article  Google Scholar 

  8. 8

    Wegrove, J. E., Kelly, D., Guitienne, P., Jaccard, Y. & Ansermet, J. P. Current-induced magnetization reversal in magnetic nanowires. Europhys. Lett. 45, 626–632 (1999).

    ADS  Article  Google Scholar 

  9. 9

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

    ADS  Article  Google Scholar 

  10. 10

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

    ADS  Article  Google Scholar 

  11. 11

    Rippard, W. H., Pufall, M. R., Kaka, S., Russek, S. E. & Silva, T. J. Direct-current induced dynamics in Co90Fe10/Ni80Fe20 point contacts. Phys. Rev. Lett. 92, 027201 (2004).

    ADS  Article  Google Scholar 

  12. 12

    Krivorotov, I. N. et al. Time-domain measurements of nanomagnet dynamics driven by spin-transfer torques. Science 307, 228–231 (2005).

    ADS  Article  Google Scholar 

  13. 13

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

    ADS  Article  Google Scholar 

  14. 14

    Shinjo, T., Okuno, T., Hassdorf, R., Shigeto, K. & Ono, T. Magnetic vortex core observation in circular dots of permalloy. Science 289, 930–932 (2000).

    ADS  Article  Google Scholar 

  15. 15

    Wachowiak, A. et al. Direct observation of internal spin structure of magnetic vortex cores. Science 298, 577–580 (2002).

    ADS  Article  Google Scholar 

  16. 16

    Guslienko, K. Yu. et al. Eigenfrequencies of vortex state excitations in magnetic submicron-size disks. J. Appl. Phys. 91, 8037–8039 (2002).

    ADS  Article  Google Scholar 

  17. 17

    Park, J. P., Eames, P., Engebretson, D. M., Berezovsky, J. & Crowell, P. A. Imaging of spin dynamics in closure domain and vortex structures. Phys. Rev. B 67, 020403(R) (2003).

    ADS  Article  Google Scholar 

  18. 18

    Choe, S.-B. et al. Vortex core-driven magnetization dynamics. Science 304, 420–422 (2004).

    ADS  Article  Google Scholar 

  19. 19

    Novosad, V. et al. Magnetic vortex resonance in patterned ferromagnetic dots. Phys. Rev. B 72, 024455 (2005).

    ADS  Article  Google Scholar 

  20. 20

    Van Waeyenberge, B. et al. Magnetic vortex core reversal by excitation with short bursts of an alternating field. Nature 444, 461–464 (2006).

    ADS  Article  Google Scholar 

  21. 21

    Yamada, K. et al. Electrical switching of a vortex core in a magnetic disk. Nature Mater. 6, 269–273 (2007).

    ADS  Article  Google Scholar 

  22. 22

    Kasai, S., Nakatani, Y., Kobayashi, K., Kohno, H. & Ono, T. Current-driven resonant excitation of magnetic vortices. Phys. Rev. Lett. 97, 107204 (2006).

    ADS  Article  Google Scholar 

  23. 23

    Bode, M. et al. Thickness dependent magnetization states of Fe islands on W(110): From single domain to vortex and diamond patterns. Appl. Phys. Lett. 84, 948–950 (2004).

    ADS  Article  Google Scholar 

  24. 24

    Cowburn, R. P., Koltsov, D. K., Adeyeye, A. O., Welland, M. E. & Tricker, D. M. Single-domain circular nanomagnets. Phys. Rev. Lett. 83, 1042–1045 (1999).

    ADS  Article  Google Scholar 

  25. 25

    Donahue, M. J. & Porter, D. G. OOMMF User’s Guide, Version 1.0. Interagency Report NISTIR 6376 (National Institute of Standards and Technology, Gaithersburg, 1999).

  26. 26

    Rahm, M., Biberger, J., Umansky, V. & Weiss, D. Vortex pinning at individual defects in magnetic nanodisks. J. Appl. Phys. 93, 7429–7431 (2003).

    ADS  Article  Google Scholar 

  27. 27

    Uhlig, T. et al. Shifting and pinning of a magnetic vortex core in a permalloy dot by a magnetic field. Phys. Rev. Lett. 95, 237205 (2005).

    ADS  Article  Google Scholar 

  28. 28

    Rippard, W. H., Pufall, M. R., Kaka, S., Silva, T. J. & Russek, S. E. Current-driven microwave dynamics in magnetic point contacts as a function of applied field angle. Phys. Rev. B 70, 100406(R) (2004).

    ADS  Article  Google Scholar 

  29. 29

    Emley, N. C. et al. Time-resolved spin-torque switching and enhanced damping in permalloy/Cu/permalloy spin-valve nanopillars. Phys. Rev. Lett. 96, 247204 (2006).

    ADS  Article  Google Scholar 

  30. 30

    Sankey, J. C. et al. Mechanisms limiting the coherence time of spontaneous magnetic oscillations driven by d.c. spin-polarized currents. Phys. Rev. B 72, 224427 (2005).

    ADS  Article  Google Scholar 

  31. 31

    Compton, R. L. & Crowell, P. A. Dynamics of a pinned magnetic vortex. Phys. Rev. Lett. 97, 137202 (2006).

    ADS  Article  Google Scholar 

  32. 32

    Kiselev, S. I. et al. Spin-transfer excitations of permalloy nanopillars for large applied currents. Phys. Rev. B 72, 064430 (2005).

    ADS  Article  Google Scholar 

  33. 33

    Lax, M. Classical noise. V. Noise in self-sustained oscillators. Phys. Rev. 160, 290–307 (1967).

    ADS  Article  Google Scholar 

  34. 34

    Kim, J.-V. Stochastic theory of spin-transfer oscillator linewidths. Phys. Rev. B 73, 174412 (2006).

    ADS  Article  Google Scholar 

  35. 35

    Xiao, J., Zangwill, A. & Stiles, M. D. Boltzmann test of Slonczewski’s theory of spin-transfer torque. Phys. Rev. B 70, 172405 (2004).

    ADS  Article  Google Scholar 

  36. 36

    Soulen, R. J. Jr et al. Measuring the spin polarization of a metal with a superconducting point contact. Science 282, 85–88 (1998).

    ADS  Article  Google Scholar 

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Acknowledgements

We thank P. Crowell for useful discussions and materials and M. Donahue for helpful guidance on the OOMMF simulations. This research was supported in part by the National Science Center through the NSEC program support for the Center for Nanoscale Systems, by ARO-DAAD19-01-1-0541 and by the Office of Naval Research/MURI program. Additional support was provided by NSF through use of the facilities of the Cornell Nanoscale Facility—NNIN and the facilities of the Cornell MRSEC.

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Correspondence to I. N. Krivorotov or R. A. Buhrman.

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Pribiag, V., Krivorotov, I., Fuchs, G. et al. Magnetic vortex oscillator driven by d.c. spin-polarized current. Nature Phys 3, 498–503 (2007). https://doi.org/10.1038/nphys619

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