Electronic and magnetic states of Mn₂ and Mn₂H on Ag(111)

Manganese dimers on Ag(111) are investigated with scanning tunneling microscopy and density functional calculations. Two species of dimers coexist that differ in their apparent heights and the absence or presence of submolecular structure. These species can be interconverted by electron and hole injection from the microscope tip. Calculations identify the two kinds of dimers as pristine Mn₂ and Mn₂H and show that hydrogen attachment to Mn₂ leads to marked changes in the dimer electronic and magnetic structure. Antiferromagnetic coupling between Mn magnetic moments in Mn₂H leaves its spectroscopic signature in the electronic structure of the monohydride compound. (paper)