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Phase-locking in double-point-contact spin-transfer devices


Spin-transfer1,2 in nanometre-scale magnetic devices results from the torque on a ferromagnet owing to its interaction with a spin-polarized current and the electrons' spin angular momentum. Experiments have detected either a reversal3,4,5,6,7,8,9,10,11,12,13,14,15,16 or high-frequency (GHz) steady-state precession17,18,19,20,21,22,23 of the magnetization in giant magnetoresistance spin valves and magnetic tunnel junctions with current densities of more than 107 A cm-2. Spin-transfer devices may enable high-density, low-power magnetic random access memory24,25 or direct-current-driven nanometre-sized microwave oscillators. Here we show that the magnetization oscillations induced by spin-transfer in two 80-nm-diameter giant-magnetoresistance point contacts in close proximity to each other can phase-lock into a single resonance over a frequency range from approximately <10 to >24 GHz for contact spacings of less than about 200 nm. The output power from these contact pairs with small spacing is approximately twice the total power from more widely spaced (400 nm and greater) contact pairs that undergo separate resonances, indicating that the closely spaced pairs are phase-locked with zero phase shift. Phase-locking may enable control of large arrays of coupled spin-transfer devices with increased power output for microwave oscillator applications.

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Figure 1: Overview of double-point-contact device.
Figure 2: High-frequency output for devices with two 80-nm point contacts and varied intercontact spacing.
Figure 3: Histograms showing statistical distribution of spin-transfer behaviour in devices with two 80-nm-diameter contacts and varied centre-to-centre contact spacing.
Figure 4: High-frequency output for two 80-nm point contacts with 150-nm intercontact spacing.


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

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  3. 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)

    CAS  Article  Google Scholar 

  4. Wegrowe, J.-E., Kelly, D., Jaccard, Y., Guittienne, Ph. & Ansermet, J.-Ph. Current-induced magnetization reversal in magnetic nanowires. Europhys. Lett. 45, 626–632 (1999)

    ADS  Article  Google Scholar 

  5. 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, 3149–3152 (2000)

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  7. 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)

    ADS  CAS  Article  Google Scholar 

  8. Urazhdin, S., Birge, N. O., Pratt, W. P. Jr & Bass, J. Current-driven magnetic excitations in permalloy-based multilayer nanopillars. Phys. Rev. Lett. 91, 146803 (2003)

    ADS  CAS  Article  Google Scholar 

  9. Mancoff, F. B. et al. Angular dependence of spin-transfer switching in a magnetic nanostructure. Appl. Phys. Lett. 83, 1596–1598 (2003)

    ADS  CAS  Article  Google Scholar 

  10. Huai, Y., Albert, F., Nguyen, P., Pakala, M. & Valet, T. Observation of spin-transfer switching in deep submicron-sized and low-resistance magnetic tunnel junctions. Appl. Phys. Lett. 84, 3118–3120 (2004)

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  12. Yagami, K., Tulapurkar, A. A., Fukushima, A. & Suzuki, Y. Low-current spin-transfer switching and its thermal durability in a low-saturation-magnetization nanomagnet. Appl. Phys. Lett. 85, 5634–5636 (2004)

    ADS  CAS  Article  Google Scholar 

  13. Jiang, Y. et al. Substantial reduction of critical current for magnetization switching in an exchange-biased spin valve. Nature Mater. 3, 361–363 (2004)

    ADS  CAS  Article  Google Scholar 

  14. Chen, T. Y., Ji, Y., Chien, C. L. & Stiles, M. D. Current-driven switching in a single exchange-biased ferromagnetic layer. Phys. Rev. Lett. 93, 026601 (2004)

    ADS  CAS  Article  Google Scholar 

  15. Lacour, D., Katine, J. A., Smith, N., Carey, M. J. & Childress, J. R. Thermal effects on the magnetic-field dependence of spin-transfer-induced magnetization reversal. Appl. Phys. Lett. 85, 4681–4683 (2004)

    ADS  CAS  Article  Google Scholar 

  16. Lee, K. J. et al. Spin transfer effect in spin-valve pillars for current-perpendicular-to-plane magnetoresistive heads. J. Appl. Phys. 95, 7423–7428 (2004)

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  19. Covington, M., AlHajDarwish, M., Ding, Y., Gokemeijer, N. J. & Seigler, M. A. Current-induced magnetization dynamics in current perpendicular to the plane spin valves. Phys. Rev. B 69, 184406 (2004)

    ADS  Article  Google Scholar 

  20. 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  CAS  Article  Google Scholar 

  21. Kiselev, S. I. et al. Current-induced nanomagnet dynamics for magnetic fields perpendicular to the sample plane. Phys. Rev. Lett. 93, 036601 (2004)

    ADS  CAS  Article  Google Scholar 

  22. 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 (2004)

    ADS  Article  Google Scholar 

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

    ADS  CAS  Article  Google Scholar 

  24. Engel, B. N. et al. A 4-Mbit toggle MRAM based on a novel bit and switching method. IEEE Trans. Mag. 41, 132–136 (2005)

    ADS  Article  Google Scholar 

  25. Parkin, S. S. P. et al. Exchange-biased magnetic tunnel junctions and application to nonvolatile magnetic random access memory. J. Appl. Phys. 85, 5828–5833 (1999)

    ADS  CAS  Article  Google Scholar 

  26. Russek, S. E., Kaka, S., Rippard, W. H., Pufall, M. R. & Silva, T. J. Finite-temperature modeling of nanoscale spin-transfer oscillators. Phys. Rev. B 71, 104425 (2005)

    ADS  Article  Google Scholar 

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We thank W. H. Rippard, T. J. Silva and S. E. Russek for discussions. This work was supported in part by the DARPA SPINS programme through Motorola.

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Correspondence to F. B. Mancoff.

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Mancoff, F., Rizzo, N., Engel, B. et al. Phase-locking in double-point-contact spin-transfer devices. Nature 437, 393–395 (2005).

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