Internal magnetic structure of Mn-12 acetate by polarized neutron diffraction

The internal magnetic structure of [Mn12O12(CD3COO)(16)(H2O)(4)]. 2CD(3)COO H . 4H(2)O as determined by polarized-beam single-crystal neutron diffracti on is reported. The standard picture, in which the inner tetrahedron of(S = 3/2) Mn4+ ions is polarized antiparallel to an outer ring of eight (S = 2) Mn3+ ions, is confirmed directly. While the total magnetization for the mo lecule is in good agreement with bulk measurements, the individual moment c omponents on each of the three symmetry-independent Mn sites are less than predicted by the standard picture. There is no evidence for net moments on the oxygen atoms, but overlap of positive and negative magnetization on the oxygen sites cannot be ruled out.