Interface effects on Gd induced disordering of Co films on Pt(111)

► Amorphization of Co films on Pt(111) by Gd overlayers depends on Co thickness. ► Gd induced relaxation in thick Co films decreases in-plane lattice constant. ► Gd induced relaxation in thin Co films increases in-plane lattice constant. ► Co-Pt interface influences the amorphization mechanism. ► Amorphization of thin Co films flips magnetization from perpendicular to parallel.