Inelastic neutron scattering study of Mn{sub 12}{endash}acetate

We report zero-field inelastic neutron scattering experiments on a deuterated powder sample of Mn{sub 12}{endash}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={minus}DS{sub z}{sup 2}{minus}{mu}{sub B}{bold B{center_dot}g{center_dot}S}{minus}AS{sub z}{sup 4}+C(S{sub +}{sup 4}+S{sub {minus}}{sup 4}) yields an anisotropy constant D=(0.54{plus_minus}0.02)K and a fourth-order diagonal anisotropy coefficient A=(1.2{plus_minus}0.1){times}10{sup {minus}3}K (the other terms being negligible). Performed in the absence of a magnetic field, our experiments do not involve the {ital g} values as fitting parameters, thereby yielding particularly reliable values of {ital D} and {ital A}. {copyright} {ital 1999 American Institute of Physics.}