Probing Structural, Electronic, and Magnetic Properties of Iron-Doped Semiconductor Clusters Fe2Gen-/0 (n=3-12) via Joint Photoelectron Spectroscopy and Density Functional Study

We present a joint experimental and theoretical study on double iron atom doped germanium clusters, Fe2Gen-\0 (n = 3-12). The experimental photoelectron spectra of cluster anions are reasonably reproduced by theoretical simulations. The low-lying structures of the iron-doped semiconductor clusters are obtained by using an ab initio computation-based genetic-algorithm global optimization method. We find that the smaller-sized Fe2Gen- (n =3-8) clusters adopt bipyramid-based geometries, while the larger ones (n >= 9) adopt polyhedral cagelike structures with one interior Fe atom. Interestingly, starting from n = 8, the most stable anionic clusters Fe2Gen- exhibit structures that are different from that of their neutral counterparts Fe2Gen. Robust ferromagnetic interaction is found between the two doped iron atoms in the neutral clusters Fe,Ge, while the total spin moment always remains at 4 mu(B) for all the neutral double iron atom doped germanium clusters up to n = 12. This behavior is in stark contrast to the magnetic quenching behavior typically observed in germanium clusters doped with a single Fe atom.