Conservation of uniaxial symmetry in Fe/Ag multilayers grown on stepped Ag(0 0 1)

Abstract

We obtained a stepped Ag(0 0 1) surface by growing a 100 nm thick Ag film on a polished MgO(0 0 1) crystal with a miscut of 1.8° in the [ 1 ̄ 1 0] direction. With scanning tunneling microscopy we observe terraces of (7±3) nm wide separated by mono-atomic steps that are straight over at least 200 nm in the [1 1 0] direction. The interface structure of Fe/Ag multilayers grown at room temperature (RT) on vicinal Ag(0 0 1) is investigated for 15 monolayers (ML) of Fe and a Ag thickness ranging from 2 to 10 ML. During Fe growth the step structure disappears at the surface of the film. When Ag is deposited on top, steps already reappear at 2 ML. For increased Ag thickness, the steps straighten out and the roughness on terraces decreases. At 8 ML of Ag the step length and surface roughness is comparable to the uncovered Ag surface. However, on larger terraces, Ag islands are observed. In addition we compare the direction of magnetization with respect to the surface normal of an [Fe(15 ML)/Ag(4 ML)] 16 multilayer grown on vicinal and flat Ag(0 0 1). For the vicinal substrate, at RT, we observe in-plane magnetization whereas for the flat substrate the magnetization is 29° out-of-plane. The results are discussed with respect to step anisotropy and step-related symmetry.