Nanoscale manganese structures on graphite studied using synchrotron radiation.

The growth mode and the electronic and magnetic properties of nanoscale Mn structures, in the form of islanded films and deposited mesoscopic clusters, have been investigated using synchrotron radiation. The Volmer-Weber growth of Mn films was studied by modelling the surface reflectivity in the extreme ultraviolet region (6-36 nm). The island growth at 423 K showed a change in growth mode as a function of coverage. Spin Polarised Photoelectron Diffraction (SPPED) from thick Mn revealed that the short range magnetic order (SRMO) is lost at a temperature of 505 K, 5.3 times the bulk Neel Temperature. Results for an islanded film, where the average island size was 6 nm, showed surprisingly that SRMO breaks down at the bulk Mn Neel temperature, with the interpretation that a complete loss of magnetic order is induced down to atomic length scales in the mesoscopic system. Core level and valence band photoemission from islanded Mn films have shown modified lineshapes in comparison to the bulk. The peak asymmetry of the 3p core level increases with decreasing particle size indicating a perturbation of the collective electron response upon the production of a core hole. The valence band and 3p core level photoemission also showed marked changes in lineshape as the temperature was increased through the bulk Mn Neel temperature. Mesoscopic Mn clusters have been deposited in-situ with the use of a high temperature gas aggregation source. Both unfiltered and size-selected 2.5 nm clusters have been investigated. Photoemission from exposed clusters showed significant changes in the Mn 3s core level line shape with respect to the bulk, interpreted as an enhanced atomic magnetic moment. Unfiltered Mn clusters were also embedded in a V matrix revealing a satellite structure in the 3s photoemission from V suggesting that the Mn clusters magnetically polarise surrounding V atoms.