Investigation of highly ferromagnetic Mn 2 Ge 4 and Mn 2 Ge 5 clusters via photoelectron spectroscopy and theoretical calculations.

We investigate the structures and properties of Mn 2 Ge 4 -/0 and Mn 2 Ge 5 -/0 by anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies (VDEs) of Mn 2 Ge 4 - and Mn 2 Ge 5 - are measured to be 2.69 eV and 2.49 eV, respectively. It is found that neutral Mn 2 Ge 4 has an approximate quadrilateral bipyramidal structure with C 2v symmetry and 11 B 2 electronic state. Neutral Mn 2 Ge 5 has a pentagonal bipyramidal structure with C 2v symmetry and 11 B 2 electronic state. The 4s-based molecular orbitals of the Mn atoms participate in the chemical bonding with the Ge 4 and Ge 5 fragments in Mn 2 Ge 4 and Mn 2 Ge 5 . In Mn 2 Ge 4 , the two Mn atoms interact with the Ge 4 moiety via four GeGeMn 3c-2e σ bonds. In Mn 2 Ge 5 , the two Mn atoms interact with the Ge 5 moiety via one MnGeMn 3c-2e σ bond and four GeMnGe 3c-2e σ bonds. The analysis of magnetic properties reveals that both Mn 2 Ge 4 and Mn 2 Ge 5 exhibit highly ferromagnetic characteristics with a magnetic moment of 10 μ B which mainly originated from the Mn atoms. These double Mn atom doped germanium clusters may provide new opportunities to design novel spintronic devices featuring high magnetic moments.