Nonadiabatic Landau-Zener tunneling in molecular nanomagnets
Laboratoire de Magnetisme Louis Néel, CNRS - BP166, 38042 Grenoble, France
2 Dipartimento di Chimica, Università di Firenze Via Maragliano 77, 50144 Firenze, Italy
3 Dipartimento di Chimica, Università di Modena Via G. Campi 183, 41100 Modena, Italy
Accepted: 16 March 2000
The Landau-Zener method allows to measure very small tunnel splittings Δ in molecular clusters Fe8. The observed oscillations of Δ as a function of the magnetic field applied along the hard anisotropy axis are explained in terms of topological quantum interference of two tunnel paths of opposite windings. Studies of the temperature dependence of the Landau-Zener transition rate P gives access to the topological quantum interference between excited spin levels. The influence of nuclear spins is demonstrated by comparing P of the standard Fe8 sample with two isotopically substituted samples. The need of a generalised Landau-Zener transition rate theory is shown.
PACS: 75.45.+j – Macroscopic quantum phenomena in magnetic systems / 75.50.Tt – Fine-particle systems / 75.60.Ej – Magnetisation curves, hysteresis, Barkhausen and related effects
© EDP Sciences, 2000