Abstract
We have measured the relaxation of the magnetization of single crystals of a Mn12 acetate complex (Mn12Ac). We were able to study the evolution of the relaxation as a function of field and temperature. For a given field and temperature, the relaxation of the bulk of the sample can be described by a single exponential relaxation time, τ. The relaxation time is observed to deviate from thermal activation at approximately 1.8 K when H = 0 tesla. Below this crossover temperature, τ tends to saturate at values of around 108 seconds. We believe that the low temperature relaxation arises from Magnetic Quantum Tunneling. We also present the hysteresis properties of Mn12Ac measured at low temperatures. The properties differ from those of ferromagnetic materials. They are not due to arrangements of magnetic domains, but to a self-induced magnetization reversal, the socalled avalanche.
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References
See for example Leggett, A.J. Chakravarty, C. Dorsey, A.T. , Fisher, M.P.A. ,Garg, A. , Zwerger, W.(1987) Dynamics of the dissipative two-state system, Rev. Mod. Phys. 59 1–84
For an excellent introduction to Quantum Tunneling of the Magnetization see Gunther ,L. (1990) Quantum tunnelling of the magnetisation, Phys. Wld. 3 28–34. For a recent review see
Stamp, P.C.E., Chudnovsky, E.M. and Barbara, B. (1992) Quantum Tunneling of the Magnetization in Solids, Int. J. Mod. Phys. B 6 1355–1473.
Chudnovsky, E.M. and Gunther,L (1988) Quantum Tunneling of Magnetization in Small Ferromagnetic Particles, Phys. Rev. Lett. 60 661–664.
Barbara, B., and Chudnovsky, E.M., (1990) Macroscopic Quantum Tunneling in Antiferromagnets, Phys. Lett. A 145205–208.
Stamp, P.C.E. (1991) Quantum Dynamics and Tunneling of Domain Walls in Feromagnetic Insulators, Phys. Rev. Lett. 66 2802–2805.
Calderia, A. O. and Leggett, A. J. (1981) Influence of Dissipation on Quantum Tunneling in Macroscopic Systems, Phys. Rev. Lett. 46 211–214.
See for example Riehenmann, W. and Nembach, E. (1984) Tunneling of domain walls in ferromagnetic materials, J. Appl. Phys. 55 1081-1091;
C. Paulsen, Sampaio,L.C., Barbara, B., Tucoulou-Tachoueres, R., Fruchard, D., Marchand, A., Tholence, J.L., Uehara, M. (1992) Macroscopic quantum tunneling of Bloch walls in small ferromagnetic particles, Europhys. Lett. 19 643–648;
Tejarda, J., Zhang, X.X., and Chudnovsky, E.M. (1993) Quantum Tunneling in random magnets, Phys. Rev. B 47 14997–14986.
Awschalom, D.D., McCord, M.A., and Grinstein, G. (1990) Oberservation of Macroscopic Spin Phenomena in Nanometer-scale Magnets, Phys. Rev. Lett. 65 783–787.
Garg, A. (1995) Suppression of Macroscopic Quantum Coherence in Magnetic Particles By Nuclear Spins, Phys. Rev. Lett. 74 1458–1461.
Sampaio, L.C., Paulsen, C. and Barbara, B. (1995) Effects of the Distribution of Energy Barriers on the Magnetic Relaxation of Ba-Ferrite Small Particles at low Temperature, to be published in J. Magn. Magn. Mater. 140–144 (1995),
Sampaio, L.C. (1994) Etude de la relaxation de l’aimantation de petites perticules et couche minces a basse temperatures, Ph.D. Thesis, Université Joseph Fourier, Grenoble, France
Street, R. and Wollley, J. C. (1949)Proc. Phys. Soc. A 62 562
For a recent review see Miller, J.S. and Epstein, A.J. (1994) Organic and Organometallic Molecular Magnetic Materials-Designer Magnets, Angew. Chem. Int. Ed. Engl 33 385–415.
Paulsen, C, Park, J.-G., Barbara, B., Sessoli, R., Caneschi, A. (1995) Novel Features in the Relaxation times of Mnl2Ac, to be published in J. Magn. Magn. Mater. 140–144
Paulsen, C, Park, J.-G., Barbara, B., Sessoli, R., Caneschi, A. (1995) Studies of hysteresis in Mn12Ac, to be published in J. Magn. Magn. Mater. 140–144
Lis, T. (1980) Preparation, Structure, and Magnetic Properties of a Dodecanuclear Mixed-Valence Manganese Carboxylate, Acta Cryst. B 36 2042–2046.
Novak,M.A. and Sessoli, R. (1995) AC Susceptibility Relaxation Studies on a Organometalic Cluster Compound: Mnl2Ac, these proceedings.
Caneschi, A., Gatteschi, G., Sessoli, R., Barra, A.L., Brunei, L.C., and Gouillot, M. (1991) Alternating Current Susceptibility, High Field Magnetization, and Millimeter Band EPR Evidence for a Ground S=10 State in Mnl2Ac, J. Am. Chem Soc. 113 5873–5874.
Caneschi, A., Gatteschi, D., Sessoli, R. and Novak, M.A. (1993) Magnetic bistability in a metal-ion cluster, Nature 365 141–143.
Sessoli, R. private communications.
Lionti, F. and Novak, M. private communications.
van Hemmen, J.L. and Sutö, S. (1986) Tunneling of Quantum Spins, Physica 141B 37–75.
Villain, J., Hartmann-Boutron, F., Sessoli, R. and Rettori, A. (1994) Magnetic Relaxation in Big Magnetic Molecules, Europhys. Lett. 27 159–164.
Politi, P., Rettori, A., Villain, J., and Hartmann-Boutron, F. (1994) Tunneling in Mesoscopic Magnetic Molecules, submitted to Phys. Rev. Lett.
Novak, M.A., Sessoli, R., Caneschi, A., Gatteschi, D. (1995) Magnetic Properties of a Mn Cluster Organic Compound, to be published in J. Magn. Magn. Mater. 145.
Bak, P. and Paczuski, M. (1993) Why Nature is Complex Physics World 6–12, 39–43
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Paulsen, C., Park, JG. (1995). Evidence for Quantum Tunneling of the Magnetization in Mn12A C. In: Gunther, L., Barbara, B. (eds) Quantum Tunneling of Magnetization — QTM ’94. NATO ASI Series, vol 301. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-0403-6_11
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DOI: https://doi.org/10.1007/978-94-011-0403-6_11
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