Heisenberg model of an {Fe8}-cubane cluster

Abstract

An analysis of the measured magnetic susceptibility of the recently synthesized magnetic molecule Fe8-cubane Fe 8 O4sao8py4 leads to a detailed proposal based on an isotropic Heisenberg model for the interactions between the eight Fe III ions. In the theoretical model, the magnetic ions are situated on the vertices of a cube with one exchange constant linking nearest neighbors and a second exchange constant appearing as a single diagonal across each of the six faces of the cube linking four of the eight ions on alternate sites. Excellent agreement between the experimental and theoretical susceptibility data is achieved, thereby providing estimates for the numerical values of the two exchange constants. Independent tests of the theoretical model are proposed in terms of inelastic neutron scattering and high-field magnetic susceptibility measurements at low temperatures that would probe the predicted low-lying magnetic energy levels of the system.