QUANTUM TUNNELING OF THE MAGNETIC-MOMENT IN MANGANESE AND IRON MOLECULAR CLUSTERS

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