STAGES OF STRUCTURAL TRANSFORMATION IN IRON THIN-FILM GROWTH ON COPPER(100)

We report on an attempt for a complete qualitative investigation of gamma --> alpha phase transformation in iron films grown at room temperature on Cu(100). To this end we characterize the surface morphology across the full transformation range using a special scanning tunneling microscope that allows imaging one particular area of the sample as it undergoes the growth induced transformation. We report for the first time, that the system is unstable toward a structural rearrangement at coverages as low as 4.6 ML, that it develops a very characteristic network of surface features and we will describe these features and their evolution in detail. The structural transformation is initiated by formation of dislocation-like thin elongated ridges which later transform into a very complicated system of bcc precipitates. Several paths of these transformations are identified. Their multiplicity reflects the complexity of processes that drive this transformation. A brief description of driving forces, a possible transformation mechanism and a correlation with magnetic properties will be given.