Spin reorientation transition induced by surface reconstruction in epitaxial Fe/Co bilayers

Surface reconstruction is a common physical phenomenon, driving the atoms near the surface to form a different spacing or symmetry from the bulk atoms to minimize the free enthalpy of the system. The formation of an asymmetric (7 × 2) reconstruction was observed on (1 1 2)-oriented Fe surface, which may be related to the anisotropic strain distribution induced by lattice mismatch. The influence of reconstruction on in-plane magnetic anisotropy has been studied in epitaxial Fe/Co bilayers grown by molecular beam epitaxy. The evolutions of Co layer thickness-dependent magnetic anisotropy for reconstructed and unreconstructed configurations were investigated by magneto-optic Kerr effect technique. The most significant difference caused by reconstruction took place when t_Co = 3 nm, showing a reconstruction-dependent in-plane spin reorientation transition with a rotation of 90°, which can be attributed to the dramatically enhanced magnetic interface anisotropy of Fe/Co bilayers.