Letter | Published:

Macroscopic quantum tunnelling of magnetization in a single crystal of nanomagnets

Naturevolume 383pages145147 (1996) | Download Citation



THE precise manner in which quantum-mechanical behaviour at the microscopic level underlies classical behaviour at the macroscopic level remains unclear, despite seventy years of theoretical investigation. Experimentally, the crossover between these regimes can be explored by looking for signatures of quantum-mechanical behaviour—such as tunneling—in macroscopic systems1. Magnetic systems (such as small grains, spin glasses and thin films) are often investigated in this way2–12 because transitions between different magnetic states can be closely monitored. But transitions between states can be induced by thermal fluctuations, as well as by tunnelling, and definitive identification of macroscopic tunnelling events in these complex systems is therefore difficult13. Here we report the results of low-temperature experiments on a single crystal composed of super-paramagnetic manganese clusters (Mn12-ac), which clearly demonstrate the existence of quantum-mechanical tunnelling of the bulk magnetization. In an applied magnetic field, the magnetization shows hysteresis loops with a distinct 'staircase' structure: the steps occur at values of the applied field where the energies of different collective spin states of the manganese clusters coincide. At these special values of the field, relaxation from one spin state to another is enhanced above the thermally activated rate by the action of resonant quantum-mechanical tunnelling. These observations corroborate the results of similar experiments performed recently on a system of oriented crystallites made from a powdered sample4.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Leggett, A. J. in Quantum Tunneling of the Magnetisation (eds Gunther, L. & Barbara, B.) 1–18 (NATO ASI Series E: Applied Sciences-Vol. 301) (Kluwer, Dordrecht, 1995)

  2. 2

    Barbara, B. et al. J. Appl. Phys. 73, 6703–6708 (1993).

  3. 3

    Barbara, B. et al. J. Mag. Magn. Mater. 140–144, 1825–1828 (1995).

  4. 4

    Friedman, J., Sarachik, M. P., Tejada, J., Maciejewski, J. & Ziolo, R. Phys. Rev. Lett. 76, 3820–3833 (1996).

  5. 5

    Barbara, B. et al. in Studies of Magnetic Properties of Fine Particles and their Relevance to Material Science (eds Dormann, J. L. & Fiorani, D.) 235–242 (Elsevier, Amsterdam, 1991).

  6. 6

    Paulsen, C. & Park, J.-G. in Quantum Tunneling of the Magnetisation (eds Gunther, L. & Barbara, B.) 189–207 (NATO ASI Series E: Applied Sciences-Vol. 301) (Kluwer, Dordrecht, 1995).

  7. 7

    Wernsdorfer, W. et al. J. Mag. Mag. Mat. 145, 33–37 (1995).

  8. 8

    Giordano, N. & Hong, K. in Quantum Tunneling of the Magnetisation (eds Gunther, L. & Barbara, B.) 257–272 (NATO ASI Series E: Applied Sciences-Vol. 301) (Kluwer, Dordrecht, 1995).

  9. 9

    Awschalom, D. D., Smyth, J. F., Grinstein, G., Di Vincenzo, D. P. & Loss, D. Phys. Rev. Lett. 68, 3092–3095 (1992).

  10. 10

    Gider, S. Awschalom, D. D., Douglas, T., Mann, S. & Chaparala, M. Science 268, 77–80 (1995).

  11. 11

    Tejada, J. Science 272, 424–424 (1996).

  12. 12

    Garg, A. Science 272, 424–425 (1996).

  13. 13

    Stamp, P. C. E. Nature 359, 366–367 (1992).

  14. 14

    Sessoli, R. et al. J. Am. Chem. Soc. 113, 5873–5874 (1991).

  15. 15

    Caneschi, A. et al. J. Am. Chem. Soc. 113, 5873–5874 (1991).

  16. 16

    Sessoli, R., Gatteschi, D., Caneschim, A. & Novak, M. A. Nature 365, 141–143 (1993).

  17. 17

    Politi, P., Rettori, A., Hartmann-Boutron, F. & Villain, J. Phys. Rev. Lett. 75, 537–540 (1995).

  18. 18

    Prokof'ev, N. V. & Stamp, P. C. E. J. Low Temp. Phys. (in the press).

  19. 19

    Burin, A., Prokof'ev, N. V. & Stamp, P. C. E. Phys. Rev. Lett. 76, 3040 (1995).

  20. 20

    Taft, K. L. et al. J. Am. Chem. Soc. 116, 823 (1994).

  21. 21

    Chudnovsky, E. M. & Di Vincenzo, D. P. Phys. Rev. B 48, 10548–10551 (1993).

Download references

Author information


  1. Laboratoire de Magnétisme Louis Néel, CNRS, BP166, 38042, Grenoble, Cedex 9, France

    • L. Thomas
    • , F. Lionti
    • , R. Ballou
    •  & B. Barbara
  2. Department of Chemistry University of Firenze, 50144, Italy

    • D. Gatteschi
    •  & R. Sessoli


  1. Search for L. Thomas in:

  2. Search for F. Lionti in:

  3. Search for R. Ballou in:

  4. Search for D. Gatteschi in:

  5. Search for R. Sessoli in:

  6. Search for B. Barbara in:

About this article

Publication history



Issue Date



Further reading


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.