Abstract
Perhaps the most anticipated, yet experimentally elusive, macroscopic quantum phenomenon1 is spin tunnelling in a ferromagnet2, which may be formulated in terms of domain wall tunnelling3,4. One approach to identifying such a process is to focus on mesoscopic systems where the number of domain walls is finite and the motion of a single wall has measurable consequences. Research of this type includes magnetotransport measurements on thin ferromagnetic wires5, and magnetization experiments on single particles6,7, nanomagnet ensembles8,9,10 and rare-earth multilayers11. A second method is to investigate macroscopic disordered ferromagnets12,13,14,15, whose dynamics are dominated by domain wall motion, and search the associated relaxation-time distribution functions for the signature of quantum effects. But whereas the classical, thermal processes that operate in these experiments are easily regulated via temperature, the quantum processes have so far not been tunable, making difficult a definitive interpretation of the results in terms of tunnelling. Here we describe a disordered magnetic system for which it is possible to adjust the quantum tunnelling probabilities. For this material, we can model both the classical, thermally activated response at high temperatures and the athermal, tunnelling behaviour at low temperatures within a unified framework, where the domain wall is described as a particle with a fixed mass. We show that it is possible to tune the quantum tunnelling processes by adjusting the ‘mass’ of this particle with an external magnetic field.
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References
Leggett, A. J. et al. Dynamics of the dissipative two-state system. Rev. Mod. Phys. 59, 1–85 (1987).
Chudnovsky, E. M. & Gunther, L. Quantum tunneling of magnetization in small ferromagnetic particles. Phys. Rev. Lett. 60, 661–664 (1988).
Stamp, P. C. E., Chudnovsky, E. M. & Barbara, B. Quantum tunneling of magnetization in solids. Int. J. Mod. Phys. B 6, 1355–1473 (1992).
Braun, H.-B., Kyriakidis, J. & Loss, D. Macroscopic quantum tunneling of ferromagnetic domain walls. Phys. Rev. B 56, 8129–8137 (1997).
Hong, K. & Giordano, N. Evidence for domain wall tunneling in a quasi-one dimensional ferromagnet. J. Phys. Condens. Matter 8, L301–L306 (1996).
Coppinger, F. et al. Single domain switching investigated using telegraph noise spectroscopy: possible evidence for macroscopic quantum tunneling. Phys. Rev. Lett. 75, 3513–3516 (1995).
Wernsdorfer, W. et al. Macroscopic quantum tunneling of magnetization of single ferrimagnetic nanoparticles of barium ferrite. Phys. Rev. Lett. 79, 4014–4017 (1997).
Awschalom, D. D., Smyth, J. F., Grinstein, G., DiVincenzo, D. P. & Loss, D. Macroscopic quantum tunneling in magnetic proteins. Phys. Rev. Lett. 68, 3092–3095 (1992).
Friedman, J. R., Sarachik, M. P., Tejada, J. & Ziolo, R. Macroscopic measurement of resonant magnetization tunneling in high-spin molecules. Phys. Rev. Lett. 76, 3830–3833 (1996).
Thomas, L. et al. Macroscopic quantum tunneling of magnetization in a single crystal of nanomagnets. Nature 383, 145–147 (1996).
Barbara, B. et al. Quantum tunnelling in magnetic particles, layers and multilayers. Phys. Scripta T 49, 268–273 (1993).
Uehara, M. & Barbara, B. Noncoherent quantum effects in the magnetization reversal of a chemically disordered magnet: SmCo3.5Cu1.5. J. Phys. 47, 235–238 (1986).
Tejada, J., Zhang, X. X. & Chudnovsky, E. M. Quantum relaxation in random magnets. Phys. Rev. B 47, 14977–14987 (1993).
Vitale, S., Cavalleri, A., Cerdonio, M., Maraner, A. & Prodi, G. A. Thermal equilibrium noise with 1/f spectrum in a ferromagnetic alloy: Anomalous temperature dependence. J. Appl. Phys. 76, 6332–6334 (1994).
Arnaudas, J. I., del Moral, A., de la Fuente, C., Ciria, M. & de Groot, P. A. J. Mesoscopic spin tunneling in the hard-random-axis-magnet amorphous alloy Tb2Fe. Phys. Rev. B 50, 547–550 (1994).
Bitko, D., Rosenbaum, T. F. & Aeppli, G. Quantum critical behavior for a model magnet. Phys. Rev. Lett. 77, 940–943 (1996).
Barbara, B. Magnetization processes in high anisotropy systems. J. Magn. Magn. Mater. 129, 79–86 (1994).
Debye, P. Polar Molecules 91–94 (Chemical Catalogue, New York, 1929).
Brooke, J., Bitko, D., Rosenbaum, T. F. & Aeppli, G. Quantum annealing of a disordered magnet. Science 284, 779–781 (1999).
Sachdev, S. Quantum Phase Transitions 39–46 (Cambridge Univ. Press, New York, 1999).
Döring, W. Z. Naturforsch. 3A, 373–379 (1948).
Kyriakidis, J. & Loss, D. Bloch oscillations of magnetic solitons in anisotropic spin-1/2 chains. Phys. Rev. B 58, 5568–5583 (1998).
Pugel, E., Shung, E., Rosenbaum, T. F. & Watkins, S. P. Local magnetometry at high fields and low temperatures using InAs Hall sensors. Appl. Phys. Lett. 71, 2205–2207 (1997).
Hansen, P. E., Johansson, T. & Nevald, R. Magnetic properties of rare-earth fluorides: ferromagnetism in LiErF4 and LiHoF4 and crystal-field parameters at the rare-earth and Li sites. Phys. Rev. B 12, 5315–5324 (1975).
Acknowledgements
We thank D. Bitko, S. Girvin, S. Nagel, P. Stamp and T. Witten for discussions. The work at the University of Chicago was supported primarily by the MRSEC Program of the National Science Foundation.
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Brooke, J., Rosenbaum, T. & Aeppli, G. Tunable quantum tunnelling of magnetic domain walls. Nature 413, 610–613 (2001). https://doi.org/10.1038/35098037
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DOI: https://doi.org/10.1038/35098037
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