MAGNETIC AND STRUCTURAL INSTABILITIES OF FERROMAGNETIC AND ANTIFERROMAGNETIC FE CU(100)/

Fe wedges epitaxially grown on Cu(100) have been employed to investiga te the interplay between magnetic and structural instabilities. 2-4 mo nolayer (ML) clean Fe films grown at room temperature are ferromagneti c with perpendicular easy axes. bcc Fe films>11 ML thick are ferromagn etic with in-plane easy axes. Most importantly, 6-11 ML fee Fe films a re antiferromagnetic and have a ferromagnetic surface. Films grown bel ow 200 K and annealed to room temperature do not exhibit the antiferro magnetic phase, but remain ferromagnetic and undergo a spin-reorientat ion transition from perpendicular to in plane at similar to 6 ML. A ne w phase diagram for Fe/Cu(100) is proposed as a function of thickness and growth temperature. In addition, an impurity-stabilized layer-by-l ayer growth that persists to 30-40 ML Fe is also reported.