Structural and magnetic studies of Co layer in epitaxially grown Fe/Co bilayers

Epitaxial Fe/Co bilayers were grown on MgO (001) substrates by molecular beam epitaxy, characterized in situ by reflection high-energy electron diffraction and ex situ by x-ray diffraction (XRD), as well as high-resolution transmission electron microscopy (HRTEM). The hexagonal close packed (hcp) structure in two perpendicular domains was identified for the Co layer using XRD and HRTEM techniques. Co is found to grow in the (11-20) orientation with the c axis in plane, parallel either to Fe[110] or Fe[1-10] The magnetic properties as a function of Co thickness in Fe (10 nm)/Co (t) (t=5-20 nm) bilayers were investigated. The Fe/Co bilayers exhibit in plane magnetization with easy axes parallel to Fe[100] and Fe[010] axes. The magnetic behavior is consistent with the orientation relationship between the Fe and Co layers.