Temperature-induced structure instability and magnetism of FeÕCu„100..

The structure and magnetism of epitaxially grown Fe films on Cu~100! at 300 K have been investigated in situ using high energy electron diffraction, low energy electron diffraction, scanning tunneling microscopy, and the magneto-optical Kerr effect. Based on a careful thickness calibration, the three well-known regions with distinct magnetic properties are determined accurately for Fe films on Cu~100!. We claim that the traditional region II should be further divided into two parts II~1! and II~2!, where the former remains region II in the traditional sense but the latter is a transition region between regions II and III. A theoretically predicted temperature driven Martensitic phase transition from face-centered-cubic ~fcc! Fe to body-centered-cubic Fe is indeed realized in the transition region II~2!.