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.
@article{arxiv.cond-mat/0408576,
title = {Exchange constants and spin dynamics in Mn12-acetate},
author = {A. Honecker and N. Fukushima and B. Normand and G. Chaboussant and H. -U. Guedel},
journal= {arXiv preprint arXiv:cond-mat/0408576},
year = {2007}
}
Comments
3 pages including 3 figures, uses elsart style files (included); to appear in JMMM (proceedings of JEMS'04)