Inelastic neutron scattering study of Mn12–acetate

We report zero-field inelastic neutron scattering experiments on a deuterated powder sample of Mn12–acetate consisting of a large number of nominally identical spin-10 magnetic clusters. Our resolution enables us to see a series of peaks corresponding to transitions between the anisotropy levels within the spin-10 manifold. A fit to the spin Hamiltonian H=−DSz2−μBB⋅g⋅S−ASz4+C(S+4+S−4) yields an anisotropy constant D=(0.54±0.02) K and a fourth-order diagonal anisotropy coefficient A=(1.2±0.1)×10−3 K (the other terms being negligible). Performed in the absence of a magnetic field, our experiments do not involve the g values as fitting parameters, thereby yielding particularly reliable values of D and A.