Electronic structure of a Mn-6 (S=4) single molecule magnet grafted on Au(111)

Single molecule magnets (SMMs) form a new class of magnetic materials consisting of identical nanoscale particles that can show magnetization in the absence of a magnetic field. We have experimentally and theoretically investigated the low-spin (S=4) member of the Mn6 SMM family, properly functionalized with two 3-thiophenecarboxylate (3tpc) ligands in order to graft it on to a Au(111) surface. We report the theoretical density of states calculated within the local density approximation (LDA) scheme accounting for the on-site Coulomb repulsion (LDA+U) for U values ranging from 0 to 8 eV. On the experimental side, by exploiting resonant photoemission at the Mn 2p edge, we were able to single out the Mn 3d derived states in the valence band energy region for a submonolayer distribution of Mn6-3tpc deposited on Au(111). From the comparison between the experimentally derived 3d density of states and the theoretical one, we found that the best agreement occurs for a U value of 4 eV. From the binding energy of Mn 2p(3/2) core line, measured in situ, we also derived a value for the 2p-3d correlation energy of about 5 eV-in agreement with previous determination.