Strain engineering of magnetic anisotropy in thin ferromagnetic films

Magnetic properties of iron films grown on Au layers with different thicknesses on a W(110) surface are studied with spin polarized low energy electron microscopy. The iron thickness for the onset of ferromagnetic order depends approximately linearly on the thickness of underlying gold film. The easy axis direction also depends upon the Au thickness. It is parallel to the tungsten [1 (1) over bar0] direction at the onset of magnetization for one and two monolayers of gold. For thicker gold films the easy axis is parallel to the [001] direction. The direction of the easy axis and the onset of ferromagnetic order are discussed in terms of magnetic anisotropies, interaction between the iron overlayer, gold and tungsten substrate, Fe film strain and morphology.