Quantum tunneling of the magnetic moment in manganese and iron molecular clusters

Molecular clusters containing a large number of metal ions have recently attracted a great deal of interest from the physics community because they exhibit the phenomenon of quantum tunneling of the magnetization (QTM). Here we present the results on two clusters, the well-known Mn12ac compound and all octanuclear iron (III) cluster, Fe8. The two clusters present some similarities, like S = 10 ground state, but are characterized by different magnetic anisotropy. Furthermore, the two systems differ in the hyperfine interactions, a term of the spin Hamiltonian whose role in QTM is still under investigation The comparison of the tunneling rate and of its field dependence in this two sq stems provides precious information on the mechanism of quantum tunneling in this class of nanosized magnetic materials. (C) 1998 Elsevier Science B.V. All rights reserved.