GROWTH AND MORPHOLOGY OF ULTRATHIN FE FILMS ON CU(001)

The relationship between magnetism and morphology of pseudomorphic ult rathin films of fee Fe on Cu(001) is reexamined in view of morphologic al data obtained with scanning tunneling microscopy. Two types of film s showing different magnetic properties were investigated. Films prepa red at 300 K are found to grow in a good layer-by-layer mode. Their ma gnetism appears to be influenced by structural instabilities connected with a martensitic fcc-->bcc transformation. Films deposited at 130 K and later annealed at 300 K grow in a Stranski-Krastanov-like mode, r esulting in a drastically different surface morphology. They are found to be structurally stable in the region where the spin reorientation takes place. An attempt is made to correlate the enhanced roughness of these films with their magnetic properties. Finally, the connection b etween the morphological percolation and the onset of long-range ferro magnetic ordering is discussed. The percolation of the first layer is found to be insufficient to establish long-range ferromagnetic orderin g in these films.