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.

Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets

Abstract

The successful operation of spin-based data storage devices depends on thermally stable magnetic bits. At the same time, the data-processing speeds required by today’s technology necessitate ultrafast switching in storage devices. Achieving both thermal stability and fast switching requires controlling the effective damping in magnetic nanoparticles. By carrying out a surface chemical analysis, we show that through exposure to ambient oxygen during processing, a nanomagnet can develop an antiferromagnetic sidewall oxide layer that has detrimental effects, which include a reduction in the thermal stability at room temperature and anomalously high magnetic damping at low temperatures. The in situ deposition of a thin Al metal layer, oxidized to completion in air, greatly reduces or eliminates these problems. This implies that the effective damping and the thermal stability of a nanomagnet can be tuned, leading to a variety of potential applications in spintronic devices such as spin-torque oscillators and patterned media.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Cross-sectional view of a nanopillar spin-valve device.
Figure 2: Spin-torque switching and magnetic-field-induced switching characteristics of an Al-passivated device.
Figure 3: Temperature dependence of coercivity and spin-torque switching currents.
Figure 4: Spin-torque phase diagrams measured at 4.2 K.

References

  1. 1

    Meiklejohn, W. H. & Bean, C. P. New magnetic anisotropy. Phys. Rev. 102, 1413–1414 (1956).

    Article  Google Scholar 

  2. 2

    Hagedorn, F. B. Exchange anisotropy in oxidized permalloy thin films at low temperatures. J. Appl. Phys. 38, 3641–3645 (1967).

    CAS  Article  Google Scholar 

  3. 3

    Patton, C. E. & Wilts, C. H. Temperature dependence of ferromagnetic resonance linewidth in thin Ni–Fe films. J. Appl. Phys. 38, 3537–3540 (1967).

    CAS  Article  Google Scholar 

  4. 4

    Nogues, J. et al. Exchange bias in nanostructures. Phys. Rep. 422, 65–117 (2005).

    Article  Google Scholar 

  5. 5

    Krivorotov, I. N., Leighton, C., Nogues, J., Schuller, I. K. & Dahlberg, E. D. Relation between exchange anisotropy and magnetization reversal asymmetry in Fe/MnF2 bilayers. Phys. Rev. B 65, 100402 (2002).

    Article  Google Scholar 

  6. 6

    McMichael, R. D., Stiles, M. D., Chen, P. J. & Egelhoff, W. F. Ferromagnetic resonance studies of NiO-coupled thin films of Ni80Fe20 . Phys. Rev. B 58, 8605–8612 (1998).

    CAS  Article  Google Scholar 

  7. 7

    Krishnan, K. M. et al. Exchange biasing of permalloy films by MnxPt1−x: Role of composition and microstructure. J. Appl. Phys. 83, 6810–6812 (1998).

    CAS  Article  Google Scholar 

  8. 8

    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).

    CAS  Article  Google Scholar 

  9. 9

    Fitzsimmons, M. R., Silva, T. J. & Crawford, T. M. Surface oxidation of permalloy thin films. Phys. Rev. B 73, 014420 (2006).

    Article  Google Scholar 

  10. 10

    Krivorotov, I. N. et al. Temperature dependence of spin-transfer-induced switching of nanomagnets. Phys. Rev. Lett. 93, 166603 (2004).

    CAS  Article  Google Scholar 

  11. 11

    Florez, S. H., Katine, J. A., Carey, M., Folks, L. & Terris, B. D. Modification of critical spin torque current induced by rf excitation. J. Appl. Phys. 103, 07A708 (2008).

    Article  Google Scholar 

  12. 12

    Kurkijarvi, J. Intrinsic fluctuations in a superconducting ring closed with a Josephson junction. Phys. Rev. B 6, 832–835 (1972).

    Article  Google Scholar 

  13. 13

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

    CAS  Article  Google Scholar 

  14. 14

    Sharrock, M. P. Time-dependent magnetic phenomena and particle-size effects in recording media. IEEE Trans. Magn. 26, 193–197 (1990).

    Article  Google Scholar 

  15. 15

    Wernsdorfer, W. et al. Experimental evidence of the Neel–Brown model of magnetization reversal. Phys. Rev. Lett. 78, 1791–1794 (1997).

    CAS  Article  Google Scholar 

  16. 16

    Leighton, C. et al. Coercivity enhancement above the Neel temperature of an antiferromagnet/ferromagnet bilayer. J. Appl. Phys. 92, 1483–1488 (2002).

    CAS  Article  Google Scholar 

  17. 17

    Fitzsimmons, M. R. et al. Influence of in-plane crystalline quality of an antiferromagnet on perpendicular exchange coupling and exchange bias. Phys. Rev. B. 65, 134436 (2002).

    Article  Google Scholar 

  18. 18

    Braganca, P. M. et al. Reducing the critical current for short-pulse spin-transfer switching of nanomagnets. Appl. Phys. Lett. 87, 112507 (2005).

    Article  Google Scholar 

  19. 19

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

    Google Scholar 

  20. 20

    Blundell, S. Magnetism in Condensed Matter 188–189 (Oxford Univ. Press, Oxford, 2001).

    Google Scholar 

  21. 21

    Gruyters, M. J. Structural and magnetic properties of transition metal oxide/metal bilayers prepared by in situ oxidation. J. Magn. Magn. Mater. 248, 248–257 (2002).

    CAS  Article  Google Scholar 

  22. 22

    Khapikov, A. F., Harrell, J. W., Fujiwara, H. & Hou, C. Temperature dependence of exchange field and coercivity in polycrystalline NiO/NiFe film with thin antiferromagnetic layer: Role of antiferromagnet grain size distribution. J. Appl. Phys. 87, 4954–4956 (2000).

    CAS  Article  Google Scholar 

  23. 23

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

    CAS  Article  Google Scholar 

  24. 24

    Compton, R. L., Pechan, M. J., Maat, S. & Fullerton, E. E. Probing the magnetic transitions in exchange-biased FePt3/Fe bilayers. Phys. Rev. B. 66, 054411 (2002).

    Article  Google Scholar 

  25. 25

    Dubowik, D. et al. Temperature dependence of ferromagnetic resonance in permalloy/NiO exchange-biased films. Eur. Phys. J. B 45, 283–288 (2005).

    CAS  Article  Google Scholar 

  26. 26

    Slonczewski, J. C. Currents and torques in metallic magnetic multilayers. J. Magn. Magn. Mater. 247, 324–338 (2002).

    CAS  Article  Google Scholar 

  27. 27

    Nadgorny, B. et al. Transport spin-polarization of NixFe1−x: Electron kinematics and band structure. Phys. Rev. B 61, R3788–R3791 (2000).

    CAS  Article  Google Scholar 

  28. 28

    Fuchs, G. D. et al. Spin-torque ferromagnetic resonance measurements of damping in nanomagnets. Appl. Phys. Lett. 91, 062507 (2007).

    Article  Google Scholar 

Download references

Acknowledgements

We thank J. C. Sankey for providing us with the macrospin simulation code and T. Hauet for helpful discussions. This work was supported in part by the Semiconductor Research Corporation, the Office of Naval Research, the NSF/NSEC program through the Cornell Center for Nanoscale Systems and an IBM-Faculty Partnership award. The work was carried out in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECS 03-35765), and it benefited from use of the facilities of the Cornell Center for Materials Research, which is supported by the NSF/MRSEC program.

Author information

Affiliations

Authors

Corresponding author

Correspondence to O. Ozatay.

Supplementary information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Ozatay, O., Gowtham, P., Tan, K. et al. Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets. Nature Mater 7, 567–573 (2008). https://doi.org/10.1038/nmat2204

Download citation

Further reading

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