Quantum Transformations of Fe8 Magnetic Nanoclusters in Megagauss Magnetic Fields

We have studied the magnetization of high-spin metal-organic clusters Fe₈ in megagauss magnetic fields at low and high temperatures. It is shown that in these mesoscopic clusters the transition from the ferrimagnetic to ferromagnetic states induced by the magnetic field is quantum in nature. At low temperatures, this transition experiences a sequence of jumps in magnetization rather than demonstrating classic, continuous behavior. These jumps are related to the intersections of the quantum energy levels of a Fe₈ cluster with increasing magnetic field. Such intersections should give rise to a change in the type of the cluster ground state, manifesting them as sharp jumps in magnetization.