Hybridization and magnetism in ultrathin Mn films

We have studied the electronic and magnetic structure of ultrathin Mn films grown on 3d transition metal surfaces using X-ray absorption and resonant photoemission. At submonolayer coverages Mn deposition leads to a highly localized 3d(5)-like ground state, A delocalized metallic ground state is formed upon increasing Mn-Mn 3d orbital overlap after percolation of the film. A similar state can also be formed through hybridization between Mn and substrate 3d states even at very low coverages. As shown by magnetic circular dichroism Mn exhibits long-range ferromagnetic order only in the latter systems, which evidences the importance of 3d hybridization for exchange coupling.