High-frequency resonant experiments in Fe-8 molecular clusters

Precise resonant experiments on Fe-8 magnetic clusters have been conducted down to 1.2 K at various transverse magnetic fields, using a cylindrical re sonator cavity with 40 different frequencies between 37 and 110 GHz. All th e observed resonances for both single crystal and oriented powder have been fitted by the eigen-states of the Hamiltonian H = -DSz2 + ESx2 - g mu(B)H. S + C(S-+(4) + S--(4)). We have identified the resonances corresponding to the coherent quantum oscillations for different orientations of spin S=10.