O. Waldmann, R. Bircher, G. Carver, A. Sieber, H. U. Güdel and H. Mutka
Exchange-coupling constants, spin density map, and Q dependence of the inelastic neutron scattering intensity in single-molecule magnets
Phys. Rev. B 75, 174438/1-11 (2007)                 

Abstract: The Q dependence of the inelastic neutron scattering (INS) intensity of transitions within the ground-state spin multiplet of single-molecule magnets is considered. For these transitions, the Q dependence is related to the spin density map in the ground state, which, in turn, is governed by the Heisenberg-exchange interactions in the cluster. This provides the possibility to infer the exchange-coupling constants from the Q dependence of the INS transitions within the spin ground state. The potential of this strategy is explored for the M=±10  ±9 transition within the S=10 multiplet of the molecule Mn₁₂ as an example. The Q dependence is calculated for powder as well as single-crystal Mn₁₂ samples for various exchange-coupling situations discussed in the literature. The results are compared to literature data on a powder sample of Mn₁₂ and to measurements on an oriented array of about 500 single crystals of Mn₁₂. The calculated Q dependence exhibits significant variation with the exchange-coupling constants, in particular, for a single-crystal sample, but the experimental findings did not permit an unambiguous determination. However, although challenging, suitable experiments are within reach of today's instruments.