Abstract of Publication No. 328
I. Mirebeau, M. Hennion,
H. Casalta, H. Andres, H. U. Güdel, A. V. Irodova and A.
We studied Mn12-acetate by inelastic neutron scattering
and diffraction. We separated the energy levels corresponding to the
splitting of the lowest S multiplet (S = 10 ground
state). The irregular spacing of the transition energies
unambiguously shows the presence of high-order terms in the spin
Hamiltonian [D = -0.457(2) cm–1,
B04 = -2.33(4)×10–5 cm–1]. The
relative intensity of the lowest energy peaks is very sensitive to
the small transverse term that is responsible for quantum tunneling,
providing the first determination of this term in zero magnetic field
[B44 = ±3.0(5)×10–5 cm–1].