The Landau-Zener method allows to measure very small tunnel splittings Δ in mol. clusters Fe8. The obsd. oscillations of Δ as a function of the magnetic field applied along the hard anisotropy axis are explained in terms of topol. quantum interference of two tunnel paths of opposite windings. Studies of the temp. dependence of the Landau-Zener transition rate P gives access to the topol. quantum interference between excited spin levels. The influence of nuclear spins is demonstrated by comparing P of the std. Fe8 sample with two isotopically substituted samples. The need of a generalized Landau-Zener transition rate theory is shown.
Nonadiabatic Landau Zener Tunneling and Quantum Phase Interference in Fe-8 Molecular Nanomagnets / W., Wernsdorfer; R., Sessoli; A., Caneschi; D., Gatteschi; Cornia, Andrea. - In: JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN. - ISSN 0031-9015. - STAMPA. - 69:(2000), pp. 375-382.