Structure of ultrathins Fe films on Cu3Au(001)

Fe films grown on Cuj1u(OOJ) single crystal at room temperature, have been studied from a structural point of view hy means of Primary-beam Diffraction Modulated Electron Emission (PDMEE), in the 0-37 monolayers (ML) thickness range. A face centered cubic (fee) structure has been found for films thinner than 4 ML. In a region ofthiekness extending up to "" 23 ML, two phases, with fee and body centered tetragonal (bet) structure, are present. For thicker films only a bet phase is detected. At 37 ML the surface layers of the film show an unstrained bcc(OOJ) structure with the [ 1001 crystal direction parallel to the [I 101 direction of the substrate.