A. Honecker, N. Fukushima, B. Normand, G. Chaboussant and H.-U. Güdel
Exchange constants and spin dynamics in Mn₁₂-acetate
J. Magn. Magn. Mater. 290-291, 966-969 (2005)                 

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.