Ultrathin Metallic Films of Manganese, Silver - and Vanadium-Manganese Grown by Molecular Beam Epitaxy.

Ultrathin metal films of Mn, AgMn and VMn etc. have been grown on Ru(001) in an MBE system for the study of the epitaxy and the magnetic properties of the first few Mn layers when the Mn lattice is expanded to match the Ru lattice. It was found that Mn can grow on Ru epitaxially layer by layer and the first two layers of Mn on Ru have an expanded structure with a Ru lattice spacing. A new phase of Mn metal formed from the third layer on up to over 60 layers. This new phase of Mn has a so-called trimerized structure with the closest approach of ~ 2.39A. Mn can also grow on Fe(100) epitaxially with an Fe spacing up to over 15 layers. The above conclusions have been demonstrated by AES, XPS, RHEED and EELFS analysis. The magnetic properties of these MBE-grown thin films have been deduced from 3s XPS multiplet splittings by comparison with all the 3d transition elements using the computer data processing technique and Doniach-Sunjic lineshape curve fittings. It was found that it is the intensity of the satellite peak, not the energy splitting, which is more sensitive to the spin polarization of 3d electrons. The satellite intensity decreases from the expanded Mn and Mn in Ag to the trimerized Mn and Mn on Fe to Mn in V. This observation is related to the lattice spacing between Mn atoms and to the thermodynamical measurements of magnetic moment for AgMn (which has 5mu _{rm B} per Mn atom) and VMn (which has no local moment). It is concluded that the satellite peak represents a 5mu_ {rm B} state which exists in every form of Mn on the time scale of 4 times 10^{-15}s and the magnetic moment of Mn atoms increases as the lattice spacing increases.