Spin Reorientation Transition Induced by Surface Reconstruction in Epitaxial Fe/Co Bilayers

Abstract 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 (112)-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 tCo = 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.