A high resolution inelastic neutron scattering (INS) study of fully deuterated Mn12-acetate provides the most accurate spin Hamiltonian parameters for this prototype single molecule magnet so far. The Mn12-clusters deviate from axial symmetry, a non-zero rhombic term in the model Hamiltonian leading to excellent agreement with observed positions and intensities of the INS peaks. The following parameter set provides the best agreement with the experimental data: D=−0.0570(1) meV, B40=−2.78(7)⋅10−6 meV, B44=−3.2(6)⋅10−6 meV and ∣\textit{E}∣=6.8(15)⋅10−4 meV. Crystal dislocations are not the likely cause of the symmetry lowering. Rather, this study lends strong support to a recently proposed model, which is based on the presence of several molecular isomers with distinct spin Hamiltonian parameters.
@article{arxiv.cond-mat/0407239,
title = {Transverse Magnetic Anisotropy in Mn12-acetate: Direct Determination by Inelastic Neutron Scattering},
author = {Roland Bircher and Gregory Chaboussant and Andreas Sieber and Hans U. Guedel and Hannu Mutka},
journal= {arXiv preprint arXiv:cond-mat/0407239},
year = {2009}
}