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Exchange couplings in the magnetic molecular cluster Mn12Ac

N. Regnault·Th. Jolicoeur·R. Sessoli·D. Gatteschi·M. Verdaguer
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Abstract

The magnetic properties of the molecular cluster Mn12Ac are due to the four Mn3+ ions which have spins S=3/2 and the eight Mn4+ ions with spins S=2. These spins are coupled by superexchange mechanism. We determine the four exchange couplings assuming a Heisenberg-type interaction between the ions. We use exact diagonalization of the spin Hamiltonian by a Lanczos algorithm and we adjust the couplings to reproduce the magnetization curve of Mn12Ac. We also impose the constraint of reproducing a gap of 35K between a S=10 ground state and a first excited state with S=9. We predict that there is an excited level with S=8 at 37K above the ground state, only slightly above the S=9 excited state which lies at 35K and the next excited state is a S=9 multiplet at 67K above the S=10 ground state.

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N. Regnault, Th. Jolicoeur, R. Sessoli, D. Gatteschi, M. Verdaguer. 2002-04-08. Exchange couplings in the magnetic molecular cluster Mn12Ac. https://doi.org/10.1103/physrevb.66.054409

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