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Exchange constants and spin dynamics in Mn12-acetate

A. Honecker·N. Fukushima·B. Normand·G. Chaboussant·H. -U. Guedel
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Abstract

We have obtained new inelastic neutron scattering (INS) data for the molecular magnet Mn12-acetate which exhibit at least six magnetic peaks in the energy range 5-35 meV. These are compared with a microscopic Heisenberg model for the 12 quantum spins localised on the Mn ions, coupled by four inequivalent magnetic exchange constants. A fit to the magnetic susceptibility under the constraint that the spin of the ground state be S=10 yields two dominant exchange constants of very similar value, J1 ~ J2 ~ 65 K (~ 5.5 meV), and two smaller exchange constants J3 and J4. We compute the low-lying excitations by exact numerical diagonalisation and demonstrate that the parameters determined from the ground state and susceptibility fit provide qualitative agreement with the excitations observed by INS.

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A. Honecker, N. Fukushima, B. Normand, G. Chaboussant, H. -U. Guedel. 2004-08-26. Exchange constants and spin dynamics in Mn12-acetate. https://doi.org/10.1016/j.jmmm.2004.11.302

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