Quantum Tunnelling of Magnetization in Uniaxial Magnetic Clusters |
| V.V. Dobrovitski, E.R. Rakhmetov Moscow State University, Physics Dept., Vorobievy gory, Moscow 119899, Russia B. Barbara CNRS - Laboratoire Louis Néel, 25, Av. des Martyrs, 38042, BP166, Grenoble, Cedex 9, France and A.K. Zvezdin Institute of General Physics of Russian Academy of Sciences, Vavilova st., 38, Moscow 117942, Russia |
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| In the present paper the uniaxial cluster, such as Mn12, is considered. For explanation of magnetization tunnelling in such a system, we propose to account for vibron excitations of Mn12 cluster; the presence of vibron can reduce the symmetry of the system and create the second-order anisotropy in the basal plane, necessary for tunnelling. Using the fact that the vibron frequency is low in comp arison with magnetic moment precession rate, we calculated the rate of magnetization tunnelling within WKB-approximation using the instanton techniques. The exact analytic instanton solution was obtained for arbitrary values of the external field, uniaxial and transversal anisotropy. We discuss also the mechanisms of quantum oscillations of the parameters of tunnelling. |
| DOI: 10.12693/APhysPolA.92.473 PACS numbers: 75.45.+j, 75.50.Tt |