Quantum transformation of spin structure of a Fe-8 nanocluster in ultrastrong magnetic fields

The transformation of the spin structure of a high-spin Fe-8 cluster in a s trong magnetic field has been investigated. The magnetization and magnetic susceptibility of the material are calculated at different external magneti c fields and temperatures. It is shown that the magnetic field induces tran sformation of the spin structure of a Fe-8 cluster from the quasi-ferrimagn etic structure with an average magnetic moment of 20 mu(B) per molecule to the quasi-ferromagnetic structure with a magnetic moment of 40 mu(B). Unlik e a similar transformation of a Neel ferrimagnet, which is continuous and o ccurs through an intermediate angular phase, this process in Fe-8 at low te mperatures manifests itself as a cascade of discrete quantum jumps, each be ing the transition accompanied by an increase in the spin number of the com plex. At high temperatures, the behavior of the magnetic cluster approaches the cluster behavior described by the classical theory. The nature of quan tum jumps is discussed in terms of the magnetic-field-induced energy level crossing in the ground state of a magnetic cluster. (C) 2000 MAIK "Nauka/In terperiodica".