Element-specific study of the anomalous magnetic interlayer coupling across NiO spacer layer in Co/NiO/Fe/Ag(001) using XMCD and XMLD

Abstract

Co/NiO/Fe trilayers are grown on Ag(001) substrate using molecular-beam epitaxy and investigated by element-specific magnetic domain images using x-ray magnetic circular dichroism and x-ray magnetic linear dichroism techniques. By comparing the Co, Fe, and NiO magnetic domain images, we identify that the anomalous Co-Fe interlayer coupling from a $90\ifmmode^\circ\else\textdegree\fi{}$ coupling to a collinear coupling with increasing the NiO film thickness is due to a transition from a collinear to $90\ifmmode^\circ\else\textdegree\fi{}$ coupling at the NiO/Fe interface while retaining a $90\ifmmode^\circ\else\textdegree\fi{}$ coupling at the Co/NiO interface. Uncompensated Ni spins are found at the Co/NiO interface but are absent at the NiO/Fe interface. No evidence of spiral NiO spin structure is found in this Co/NiO/Fe sandwich.