Structural and magnetic anisotropies of Fe/ZnSe(001) thin films

The morphology, the atomic structure, and the strain of very thin Fe epilayers grown on ZnSe(001) have been studied by combined scanning tunnel microscope (STM) and extended x-ray-absorption fine-structure experiments. It turns out that the crystal structure of the flat and anisotropic islands (up to 5 monolayers) and terraces (higher coverages) observed by STM is close to bulk iron but affected by a weak out-of-plane tetragonal distortion. Strain measurements and magnetic anisotropy constants of very thin films obtained by ferromagnetic resonance measurements allow us to conclude that the important out-of-plane anisotropy term is determined by the interface atomic structure. Finally, we put forward two hypotheses to explain why the measured out-of-plane anisotropy is one order of magnitude larger than the [110] in-plane anisotropy. The former is related to a disordered configuration of iron and zinc atoms between bonding and antibonding sites at the interface. The latter hypothesis is related to the direction of the demagnetization field due to the morphology of iron films.